Women and Exercise - Physiology and Sports Medicine

32 Basic Concepts of Exercise Physiology EXERCISE AND WEIGHT have found that combining exercise and di- CONTROL etary change produces greater weight loss than diet change alone. Data reveal a pattern of weight regain when dietary interventions are used alone It appears, however, that exercise exerts a to control weight, whereas diet combined special impact on weight maintenance. Be- with exercise leads to better maintenance.29 havior modification dietary programs, ex- The importance of exercise for weight con- ercise, and combinations of diet and exer- trol is clear: regular exercise is a central cise have about the same short-term effect component of losing weight and is the single on weight loss.26 Thus, physical activity has best predictor of long-term weight mainte- a modest effect on initial weight loss, per- nance.11'29-37 haps because dietary compliance is good early in a program and there is little room Correlational studies reveal consistently for additional weight loss. However, long- that exercise is associated with successful term effects are clear: exercise is critical for weight loss and maintenance.35,38-41Kayman weight maintenance. When the participants and associates35 studied formerly obese in experimental studies are followed for 1 or women who lost weight and kept it off and 2 years, striking effects of exercise emerge. compared them with obese women who had A study by Pavlou and colleagues29 provides lost weight and regained. Of the maintain- persuasive evidence for the benefit of exer- ers, 90% were exercising regularly (mini- cise in weight maintenance—regardlessof mum of three times a week for >30 min- the type of dietary intervention. In this utes), compared to only 34% of the regainers study, 160 male members of the Boston Po- (Fig. 2-3). lice Department and the Metropolitan Dis- trict Commission were randomly assigned Experimental weight loss treatment stud- to one of four 12-week programs (balanced ies with random assignment and control caloric-deficit diet [BCDD] of 100 kcal; a groups comparing exercise to no exercise ketogenic protein-sparing modified fast provide the strongest scientific support for [PSMF]; and two liquid forms of these bal- the role of exercise in weight control. Many anced and ketogenic diets [DPC-70 and DPC- of these studies,29,34,37,42-46 but not all,47-49 Figure 2-3. Maintenance and re- lapse after weight loss in women. (Adapted from Kayman et al,35 p 803, with permission.)

Exercise and Regulation of Body Weight 33 800]) and to either an exercise or nonexer- which bolster energy expenditure by as lit- cise group. Figure 2-4 displays 8- and 18- tle as 200 to 400 calories per day, result in month follow-up data,29 showing no differ- enhanced maintenance in children.51,52 We ence between the initial and the 18-month would like to underscore the connection be- follow-up weight for those who did not ex- tween exercise and weight maintenance, be- ercise, regardless of the four types of diets cause for many people, keeping the weight used for weight loss. In sharp contrast, the off is a greater challenge than losing weight exercise group maintained weight loss. Fur- initially. thermore, whether one added or stopped exercise following treatment predicted LIKELY MECHANISMS LINKING weight maintenance. As shown in Fig. 2-5, EXERCISE AND WEIGHT participants who ceased exercise at the end CONTROL of treatment regained weight, whereas those who started exercise at the end of treatment Conventional wisdom suggests that over- maintained their weight loss at an 18-month weight persons should exercise more, pre- follow-up. In sum, exercisers were much less sumably because \"it burns calories.\" It is likely to regain their weight during follow- unlikely, however, that exercise exerts its up. No comparable studies have been per- powerful effects on weight control simply formed using women, but we may tentatively because it burns calories. Exercise can alter assume that the findings would be similar. body weight, body composition, appetite, and basal metabolism, and can affect health, Exercise facilitates maintenance with independent of weight loss. Moreover, ex- both balanced diets29,50 and very low calorie ercise can enhance psychologic well-being, diets.29,37 Furthermore, even minimal in- improve self-esteem, and increase motiva- creases in lifestyle activities (e.g., walking instead of riding,doing errands by walking), Figure 2-4. Exercise as an adjunct to weight-loss maintenance in moderately obese subjects. Follow-up data after 18 months confirm the long-term effectiveness of exercise intervention for as short a period as 8 weeks. There is no difference between initial and 18-month follow-up weight for those who did not exercise, regardless of the diet used for weight loss. In contrast, the exercise group maintained weight loss. (From Pavlou et al,29 p 1121,with permission.)

34 Basic Concepts of Exercise Physiology Figure 2-5. The addition or removal of learned exercise would appear to be a major contributing factor relative to weight maintenance.Subjects who ceased exercise regained or demonstrated a strong tendency to return to pre- study weights. Poststudy introduction of exercise (learned but nonsupervised) creates a positive effect. (Numberof subjects given in parentheses.) (From Pavlou et al,29 p 1122, with permission.) tion. Although the exact links are not fully for individuals. For example, if metabolic understood, there are multiple pathways by variables emerge as important, the types which exercise may aid in weight control and amount of exercise needed to boost (Table 2-1). metabolic rate should be prescribed. If psy- chologic mechanisms are important, consis- Understanding the potential mechanisms tency, rather than type or amount, may be is crucial for prescribing exercise programs the central feature of a program. As a result, different programs might be prescribed de- Table 2-1. POSSIBLE LINKS BETWEEN pending on the nature of the links between EXERCISE AND WEIGHT CONTROL exercise and weight control. 1. Exerciseexpends energy. 2. Exercisemay decrease appetite. Energy Expenditure 3. Exercise may enhance metabolicrate. 4. Exercise may preserve lean body tissue. Exercise Expends Energy 5. Exercise may limit preference for dietary fat. 6. Exercise enhanceshealth. Any activity uses energy, so any increase 7. Exercise improves risk factors associated with in activity can aid in weight control. Table 2- 2 provides values for caloric expenditure of overweight. various physical activities. Several impor- 8. Exercisehas positive psychologic effects: tant points are highlighted by this chart. First, routine activities like using stairs and Improves self-esteem and psychologicwell- walking are useful ways of expending en- being, ergy. For example, walking up and down two Decreases mild stress and anxiety, Increases confidence, May enhance dietaryadherence. Source: Adapted from Grilo et al.,26 p 257, with permission.

Exercise and Regulation of Body Weight 35 Table 2-2. CALORIC VALUES FOR 10 Body Weight MINUTES OF ACTIVITY 125 175 250 20 28 40 Body Weight 35 48 69 32 44 64 125 175 250 28 40 57 32 44 64 Personal Necessities 10 14 20 Light Work 29 40 58 Sleeping 10 14 18 Assembly line 56 78 110 Sitting (watching TV) 15 21 30 Auto repair 60 84 121 Sitting (talking) 26 37 53 Carpentry 158 220 315 Dressing or washing 12 16 24 Bricklaying 79 111 159 Standing Farming chores 43 65 94 House painting 39 54 78 Locomotion 56 78 111 58 82 117 Walking downstairs 146 202 288 Heavy Work 56 78 111 Walking upstairs 29 40 58 Pick and shovel work 90 128 182 Walking at 2 mph 52 72 102 Chopping wood 35 48 69 Walking at 4 mph 90 125 178 Dragging logs 48 66 94 Running at 5.5 mph 118 164 232 Drilling coal 69 96 137 Running at 7 mph 164 228 326 33 48 68 Running at 12 mph 42 58 83 Recreation 56 78 112 Cycling at 5.5 mph 89 124 178 Badminton 32 45 64 Cycling at 13 mph Baseball 75 104 144 Basketball 80 112 160 Housework Bowling (nonstop) 60 88 130 Canoeing (4 mph) 98 138 194 Making beds 32 46 65 Dancing (moderate) 75 104 144 Washing floors 38 53 75 Dancing (vigorous) 32 45 64 Washing windows 35 48 69 Football 40 56 80 Dusting 22 31 44 Golfing 56 80 115 Preparing a meal 32 46 65 Horseback riding 43 65 94 Shoveling snow 65 89 130 Ping-pong Light gardening 30 42 59 Racquetball Weeding garden 49 68 98 Skiing (alpine) Mowing grass (power) 34 47 67 Skiing (water) Mowing grass (manual) 38 52 74 Skiing (cross-country) Squash Sedentary Occupation 15 21 30 Swimming (backstroke) Silting writing 25 34 50 Swimming (crawl) Light office work 20 28 40 Tennis Standing, lightactivity 19 27 39 Volleyball Typing (electric) Source: From Brownell,135 pp 66-67, with permission. flights of stairs per day, in place of using an typical fast-food meal consisting of a quar- elevator, would account for approximately6 ter-pound cheeseburger, a small order of Ib of weight loss per year for an average- french fries, and a chocolate shake contains weight man.53 Second, heavier people burn about 1100calories. To expend 1100 calories more calories than normal-weight people through exercise would require running 11 while doing the same activity, because more miles or playing tennis for 3 hours. energy is required to move the extra mass. However, Bray55 and others have ob- Despite these facts, many people are dis- served that weight loss in people who exer- appointed when they learn that even very cise tends to be greater than would be ex- rigorous physical activities produce rela- pected through the direct expenditure of tively small energy deficits.54 For example, a energy. Consequently,other physiologic or

36 Basic Concepts of Exercise Physiology psychologic mechanisms are likely to be im- ventions with weight-cyclers, as they may portant. bolster RMR.46 Exercise May Enhance Metabolic Rate Appetite and Hunger Resting metabolic rate (RMR) accounts Exercise May Decrease Appetite for approximately 60% to 75% of a person's total daily energy needs.55–57 Thus, small A number of studies with both humans changes that either decrease or increase and animals have examined the association RMR can have a dramatic effect on a per- between exercise and appetite.26 A frequent son's total daily energy expenditure. For in- misconception is that increased activity will stance, dieting can lead to a rapid andsig- be met with increased food intake, so there nificant reduction in RMR.55,57–62 Since is no net benefit of the exercise. Although dieting and weight loss often lower RMR, it the effects of exercise on appetite are com- is important to find ways to help offset this plex, this regulatory mechanism tends to be metabolic slowdown.57,63 in effect for only certain levels ofactivity.26 Exercise may prevent or at least reduce Studies with humans suggest that exercise the decline in the body's metabolic rate pro- can be effective in regulating appetite. In- duced by dieting.57,60,64,65 Tremblay and creasing physical activity moderately tends colleagues65 found a significant increase in to decrease appetite, food intake, and body RMR (8% of pretraining value) in obese in- weight, whereas increasing exercise to vig- dividuals who engaged in an 11-week train- orous levels leads to increased appetite but ing program, despite significant reductions stable body weight.67–70 However, women in body weight and body fat mass. Broeder may benefit less from the suppression ef- and colleagues66 observed that 12 weeks of fects of exercise on appetite than do men.67 either high-intensity endurance or resist- Some studies have found that increased ance training helped to prevent an attenua- physical activity does not decrease appetite tion in RMR normally observed during ex- in lean women, and that they may in fact eat tended periods of negative energy balance, more,67,70,71 although their appetite does not by either preserving the person's fat-free appear to increase beyond the level needed mass via endurance training, or increasing it to maintain weight. via resistance training. In contrast, Phinney and colleagues49 found that when physical In sum, exercise is unlikely to increase ap- activity was added while on a very low cal- petite beyond the level to keep body weight orie diet, it further depressed the metabolic stable, and often may lead to decreased food rate rather than raised it. These conflicting intake. However, a potential problem exists, findings underscore the need for more re- since people may \"believe\" they will be hun- search to define the amount and types of ex- grier after they exercise. Monitoring one's ercise that have the most beneficial meta- feelings of hunger before and after exercise bolic effects. may help dispel this myth. In fact, some in- dividuals find it useful to exercise at times Another dilemma confronting dieters is when they are tempted to overeat. the potential metabolic consequences of successive episodes of weight loss followed Exercise May Limit Preference for by regain (i.e., weight cycling or yo-yo diet- Dietary Fat ing). There is inconclusive evidence about whether weight cycling produces greater Another potential benefit of exercise may drops in RMRwith repeated dieting efforts.26 be its influence on the intake of fat in the To the extent that this does occur, it may be diet. Several animal studies have found that particularly important to use exercise inter- weight cycling (repeated cycles of weight

Exercise and Regulation of Body Weight 37 loss and regain) results in a highercon- exists that regular physical activity is asso- sumption of dietary fat,72,73 accompanied by ciated with good health.82–84 Moreover, even larger adipose tissue depots.72 Exercise, modest levels of exercise are sufficient for however, seems to limit this increased di- significant health benefits.79,85,86 Lee87 re- etary fat selection in weight-cycled female viewed the literature pertaining to women rats, and reduces the amount of body fat re- and aerobic exercise and concluded that gained during refeeding periods.73 These middle-aged and older women incur the findings may have important implications same physiologic and health benefits from for the treatment of overweight in humans, exercise as do men (see Appendices 2-1 and since weight cycling is common. 2-2). Body Composition One study provides convincing evidence Exercise May Preserve Lean (Muscle) that even low levels of activity can have Tissue a substantial health impact. Blair and colleagues79 calculated the age-adjusted all- Unfortunately, weight loss is not due cause death rates over an 8-year period in solely to the loss of body fat. Weight loss is 10,224 men and 3120 women who were ap- accounted for by several changes, including parently healthy at baseline. Each person the loss of both lean and fat body tissue. As was assigned to a fitness category (based on much as 25% of the weight lost by dieting entry maximal treadmill testing), ranging alone can be lean body mass (LBM).57 In from the very unfit (Fitness Level 1) to the fact, the often observed slowing of weight very fit (Fitness Level 5). In all BMI strata, loss despite continued dieting (reaching a the low-fit men and women had higher death plateau) may be due partly to the loss of lean rates than moderate- and high-fit subjects. tissue, since lean tissue requires more en- Therefore, physically fit individuals had ergy to sustain itself. much lower mortality rates (Fig. 2-6). The largest reductions in risk, however, came The loss of LBM decreases when exercise from moving from very low to moderate lev- (even low to moderate) is combined with els of fitness, not from being extremely ac- diet.74 Several studies have found that regu- tive. This study and others have helped lar aerobic exercise, even in the absence of counter the notion that one must exercise dietary restriction, can produce significant vigorously to obtain the health benefits of body fat loss with minimal loss of lean tis- exercise,83,85 and is critically important for sue.75–77 More recently, resistance training overweight persons, in whom adherence is has been used to improve the ratio of lean to fat tissue, which may have the added benefit of increasing energy expenditure.78 Since in- creasing LBMand decreasing body fat may increase metabolic rate (because muscle re- quires more calories than does fat), exercise prescriptions with this goal in mind may be especially useful. Physical Activity and Health Figure 2-6.The relationship between fitness level and death rate in women. (From Brownell,135 p 178, with Prospective studies reveal an inverse re- permission, based on findings of Blair et al.79) lationship between exercise or fitness level and morbidity and mortality in overweight men and women.79–82 Substantial evidence

38 Basic Concepts of Exercise Physiology greatest in the low to moderate intensity diet was related to adherence to exercise, range.5,33,51 and that adherence was better in programs with lower rather than higher caloric expen- Exercise Improves Medical Conditions diture. Often Associated with Overweight In these studies,51,96 low calorie expendi- Exercise helps offset medical conditions ture was related to increased dietary adher- prevalent in the overweight. Conditions ence and weight loss. Physiologic factors such as high blood pressure, elevated cho- (e.g., increased metabolic rate) alone can- lesterol, and diabetes improve with exer- not account for the weight loss when the cise.83 Exercise can provide these benefits amount of exercise is so minimal. These independent of weight loss.53,54,83,88,89 Several findings raise the important issue of studies have now shown an association be- whether perceived or actual fitness is the tween distribution of body fat (abdomi- key factor in linking exercise to weight con- nal fat) and increased health risk (e.g., trol. Since adherence is better for low- to higher incidence of myocardial infarctions moderate-intensity exercise, low levels may and strokes).90 Recent population-based evoke feelings of mastery. Improved self- studies show that physically active men and concept due to exercising may then gener- women have lower (more favorable)waist- alize to other aspects of functioning, thereby to-hip ratios.91–94 Therefore, in the absence increasing confidence for controlling di- of clinical intervention data, it seems rea- etary practices. One's perception of being sonable to recommend exercise for over- physically fit thus may be more important weight persons with a high waist-to-hip than physical fitness per se.95 Developing ratio, although research is needed to docu- the self-image of an exerciser should en- ment whether exercise reduces abdominal hance self-efficacy, which could lead to in- fat. creased self-determination. Psychologic Changes Collectively, these studies show that ex- Exercise has important psychologic ef- ercise of low to moderate intensity is asso- ciated with improved dietary patterns and fects and is associated with positive psycho- weight loss. These results parallel others logic health. Physical activity improves that suggest that exercise may not need to mood, psychologic well-being (especially be aerobic or of high intensity to engender immediately following exercise), and self- positive psychologic correlates.98–101 In- concept, and also decreases mild anxiety, deed, high-intensity exercise can increase depression, and stress.95,96 In persons at- negative mood states such as tension,anxi- tempting to lose or maintain weight, exer- ety, and fatigue.102 Such negative conse- cise may relieve stress or other negative quences are important to avoid, since they feelings that precede dietary lapses.97 represent potential barriers to exercise ad- herence. Surprisingly low levels of exercise seem to complement dieting by increasing dietary In sum, exercise is an importantpredictor adherence.51,96 Rodin and Plante96 reported of success at weight reduction and mainte- that findings from their weight control stud- nance and has numerous health and ies suggest that people who engage in mod- psychologic benefits. The link between ex- est exercise (i.e., jumping jacks for 10 min- ercise, weight control, and positive psycho- utes a day, three times a week) are logic functioning dictates the importanceof substantially more successful at weightcon- finding strategies to help individuals be- trol than nonexercisers. Similarly, Epstein come more active. In the next section, we and colleagues51 found that adherence to will discuss the challenge of adherence and suggest ways to maximize an overweight person's ability to complywith exercise reg- imens.

Exercise and Regulation of Body Weight 39 THE CHALLENGE OF Table 2-3. POTENTIAL PHYSICAL AND ADHERENCE PSYCHOLOGIC BARRIERS TO EXERCISE IN OVERWEIGHT PERSONS Poor adherence has long been considered a challenge in exercise programs. Although Physical Barriers there have been over 200studies conducted Poor fitness in the past 20years on various determinants Excess weight of exercise behavior,103 little systematic in- vestigation has been conducted on over- Psychologic Barriers weight persons. We will draw from the exist- Negative experiences ing studies on adherence relevant for overweight persons and suggest ways to de- Teased by peers velop a program. The reader is referred to Picked last for teams prior reviews for a more general overviewof Social Anxiety exercise adherence, since they provide Shame of being observed a framework from which a program for Body image dissatisfaction the overweight individual can be estab- Lack of confidence lished.5,26,83,103 Lack of knowledge or experience Source: Adapted from Grilo et al,26 p 264, with Adherence and the permission. Demographics of Obesity physical and psychologic barriers to exer- Although most people who are over- cise among overweight individuals is criti- weight know that increased exercise may cal. Table 2-3 summarizespotential barriers help them lose weight, many are unable to to exercise. establish and maintain a personal exercise program. Professionals are confronted with Physical Burden the challenge of helping these individuals increase their level of physical activity. For many overweight persons, exercise is unpleasant due to poor physical condition- One reason that exercise adherence is a ing and excess weight. Weight becomes a special challenge in overweight persons is burden that must be overcome. Increasing that groups most likelyto be overweight are physical activity may be difficult, painful, also least likely to exercise. Overweight oc- and fatiguing. Startinga program too quickly curs with especially high prevalence in mi- or vigorously may lead to excess fatigue, nority populations104,105and in persons with physical discomfort, and injuries, each of lower socioeconomic status (SES).21,106 In ad- which can deter a person from future efforts. dition, the incidence of obesity increases Starting overweight people with a low- to with age, particularly in women.21,107 For Af- moderate-paced program is crucial for pre- rican-American women ages 45 to 75 years, venting injuries, enhancing exercise self- obesity rates are as high as 60%.21 Exercise efficacy, and sustaining adherence. rates for obese persons, the elderly,minor- ity groups, and those with low SES, however, Negative Associations are very low.103,108 Psychologic barriers are sometimes for- Obstacles to Exercise for the midable obstacles for overweight people to Overweight Individual overcome in order to exercise regularly.For people who have been overweight since Several obstacles can impede the transi- childhood, early memories such as being tion from the desire to exercise to the actof teased, being picked last for teams, and suf- exercising. Careful attention to potential fering from poor athletic performance leave many obese persons ashamed and self-con- scious about their bodies.109,110 Overweightis

40 Basic Concepts of Exercise Physiology often associated with social rejection.111,112 diet for weight control. It will be important Consequently, many overweight persons to keep this inexperience in mind when de- manifest disturbances in areas of life af- veloping exercise programs for these indi- fected by weight, such as body image, social viduals. interactions, and self-esteem.112 Adherence Studies It is not surprising that thoughts of exer- Exercise adherence has been understud- cise may evoke unpleasant memories, feel- ings of inadequacy, and shame at the pros- ied with overweight persons. This is unfor- pect of being observed. Not only does the tunate, since overweight persons have low excess weight add a physical burden, but a exercise participation rates and are at a high persistent negative body image may dis- risk for health problems that can be im- courage a person from exercising withoth- proved with exercise.103 For instance, ers, and the lack of self-confidence maypre- Gwinup115 found that only 32%of overweight vent a person from starting an exercise women enrolled in a walking exercise pro- program. It is important to be sensitive to gram remained in the program for 1year. In such experiences and to create a supportive a prospective study with a large community atmosphere so that overweight persons can sample, Sallis and co-workers116 found that identify and initiate activities they enjoy in a overweight subjects were less likely to adopt positive way. Helping overweight persons exercise than were normal-weightsubjects. identify clothing that they feel comfortable wearing, from shoes to workout apparel, and Intensity explaining where to obtain exerciseclothing in large sizes is useful and appreciated. It is Less intense, \"lifestyle\" activity or mod- essential to encourage patients to experi- erate-intensity activities (those that require ment with different activities until they ex- less than 60% of maximal capacity, such as perience pleasure and satisfaction. This walking) generally have superior initiation may include exploring community options and adherence rates and lower drop-out that provide opportunities to exercise with rates than do vigorous activities.51,83,87,116,117 other overweight individuals. This seems to hold true among widely di- verse groups of people. A large community Developmental and Gender Issues study in California116 found that both men and women were more likely to adopt mod- Exercise initiation and maintenance may erate activity than a vigorous fitness regi- be enhanced by tailoring interventions to men. Moderate activity programs showed a specific developmental milestones.113An ex- dropout rate (25% to 35%) roughly one half ecutive woman with an ill mother will have of that seen for vigorous exercise (50%). Ad- different developmental and practical issues ditionally, moderate activity appears to be than a teenager with minimal responsibili- more readily maintained over the life span, ties. Table 2-4 presents features and exam- whereas participation in vigorous activity ples of physical activity programs for sev- declines dramaticallywith age.118 This is es- eral important periods. It is also important pecially important to consider with over- to tailor interventions specifically for weight persons, since overweight increases women. For example, manywomen have not with age. In fact, low-intensityexercise (30% been involved in physical activity programs. to 45% MHR) has produced significant in- The fact that inactivityis considered a prob- creases in fitness for women in their 60s and lem for women reflects a substantial shift in 70s.119 Overweight children also do better attitudes in the past 25 years.114 Many when low-intensity, lifestyle exercise regi- women over 30 were never encouraged to mens are prescribed, versus high-intensity participate in team sports or recreational activities; Epstein and colleagues52,120 found physical activity; instead, many learned to

Exercise and Regulation of Body Weight 41 Table 2-4. PHYSICALACTIVITY PROGRAMS FOR SEVERAL MAJOR DEVELOPMENTAL MILESTONES Milestone Goals/Strategies (Critical Period) Specific Features Adolescence Rapid physical and emotional changes Exercise as part of a program of healthyweight Initial work entry Increased concern with appearance regulation (both sexes) and weight Noncompetitive activities that are fun, varied Need for independence Emphasis on independence, choice Short-term perspective Focus on proximal outcomes (e.g., body image, Increased peer influence Increased time and scheduling stress management) Peer involvement, support constraints Choice of activities that are convenient, enjoyable Short-term perspective Focus on proximal outcomes Employer demands Involvement of worksite (environmental Parenting Increased family demands and time prompts, incentives) constraints Realistic goal setting, injury prevention Coeducational, noncompetitive activities Family-directed focus Emphasis on benefits to self and family (e.g., Postpartum effects on weight, mood stress management, weight control, well-being) Retirement age Increased time availability and Activities appropriate with children (e.g., flexibility walking) Longer-term perspective on health; Flexible, convenient, personalized regimen increased health concerns, Inclusion of activities of daily living \"readiness\" Neighborhood involvement, focus Family-based public monitoring, goal-setting Caregiving duties, responsibilities Availability of child-related services (child care) (parents, spouse, children, or Identification of current and previous enjoyable grandchildren) activities Matching of activities to current health status Emphasis on mild- and moderate-intensity activities, including activities of daily living Use of \"life path point\" information and prompts Emphasis on activities engendering independence Garnering support of family members, peers Availability of necessary services (e.g., caretaking services for significant other) Source: From King,113 p 250, with permission. that lifestyle exercise was superior to pro- extreme effort. Adherence is increased grammed aerobic exercise for long-term when the activity can be readily incorpo- weight maintenance (Fig. 2-7). It may be rated into daily life; this, in turn, may en- that since lifestyle programs are moreflexi- hance one's confidence in the ability to per- ble and easily incorporated into one's daily form physical activity (self-efficacy), which routine, fewer barriers emerge to preclude may improve adherence. Moderate-inten- continued participation.51,121 sity activity has many of the health benefits of vigorous exercise,79,116,122 with the added In sum, prescription of lifestyle activity benefit of easier maintenance.83 over vigorous, programmed exercise may represent one key to adherence for over- Relapse Prevention Strategies weight persons. Beginning individuals with Cognitive behavioral therapy (CBT) pro- modest activity goals that are readily incor- porated into their daily life is preferable to grams for exercise adherence that have in- approaches that promote sweat, pain, and

42 Basic Concepts of Exercise Physiology Figure 2-7. Percent overweight for children in three groups (calis- thenics, programmed aerobic ex- ercise, and lifestyle exercise) at 0, 2, 6, 12, and 24 months. (From Ep- stein et al,120 p 351, with permis- sion.) corporated components of Marlatt and nance of exercise and proposed that indi- Gordon's123 relapse prevention model result viduals in the different stages may require in better physical activity rates at follow- different cognitive and behavioral ap- up.124–128 Although originally developed for proaches.5,129,130 This model proposes that other areas such as smoking and alcohol, people proceed through five stages: precon- this model offers several important sugges- templation, contemplation, preparation, ac- tions to persons trying to maintain any be- tion, and maintenance, as follows:131 havior change. Three elements are particu- larly useful for increasing adherence: (1) Precontemplation. Precontemplators do flexible rather than rigid exercise goals,128 not intend to change their behavior in (2) training individuals in specific tech- the foreseeable future. These individu- niques to cope with missed exercise ses- als are unaware of the benefits of exer- sions,126 and (3) identifying potential situa- cise or are uncertain about whether the tions that might interfere with exercise or benefits are greater than the negative lifestyle changes and developing plans for aspects. Movement to the next stage coping with those high-risk situations and would require acknowledging and be- setbacks.124 Moreover, relapse training, in coming more aware of the negative as- comparison to a treatment with no relapse pects of their lack of exercise. training, results in significantly greater weight maintenance.124 Even minimal inter- Contemplation. Contemplators are aware vention strategies such as telephone con- of the negative aspects of their lack of tacts or mailings,however, may enhance ad- exercise and are seriously considering herence and maintenance of weight loss.31,36 taking action. Both the positive and negative aspects are considered. Con- Stages of Change in Exercise Adoption templators have not, however,commit- and Maintenance ted themselves to the necessary steps for change. Exercisers will progress to Recently, several researchers have sug- the next stage only after a decision to gested that individuals proceed through change their lack of exercise. specific stages in the initiation and mainte- Preparation. Exercisers in the prepara- tion stage are characterized by a readi-

Exercise and Regulation of Body Weight 43 ness and intention to begin exercise or study134 found a significant interaction be- change their behavior in the foreseea- tween weight loss treatment and gender: ble future. These individuals have eval- women did better when treated with their uated past successes and failures and spouses, whereas men did better when are on the verge of takingaction. Move- treated alone. This study is an example of ment to the next stage requires setting the potential need to match particular sup- attainable goals and steps for action. port interventions to the individual's needs Action. Persons in the action stage begin and characteristics. to make changes in their behavior. A central focus is setting appropriate Equivalent studies looking at social sup- goals and taking action to implement port and exercise adherence in overweight them. They are aware of the cognitive, persons have not been done. Our clinical ex- behavioral, and/or environmental fac- perience suggests, however, that there tend tors that may interfere with continued to be \"solo\" versus \"social\" exercisers. The progress. \"solo\" type individual typicallydoes not de- Maintenance. Persons in the mainte- sire the company of others and tends to se- nance stage focus their attention on lect activities such as walking or jogging preventing relapse to former behaviors alone. A \"social\" exerciser may prefer an as well as continuing the exercise pat- aerobics class or jogging with a partner. Our terns begun in the action stage. Exercis- experience is that a better match between ers in the maintenance stage are con- personality type and type of exercise results centrating on identifying potential in a better fit.135 situations that may interfere with their continued success. Further research is needed to identify the A potential major contribution of this factors that predict success with spouse, model for increasing and maintaining exer- family, or peer interventions for exercise cise lies in its consideration of the readiness and dietary adherence with obese persons. of individuals for change.5 Awareness of Brownell135 and Brownell and Rodin136 pro- variables such as readiness can facilitate pa- vide specific strategies and techniques to tient-treatment matching, thus improving aid overweight individuals in identifying outcome.132 In fact, a recent study129 found and pursuing the type of social support they that exercise programs must accommodate need. the large percentage of individualswho are not ready to change their exercise habits. PROGRAM Research is needed on how to best match RECOMMENDATIONS exercise interventions to patient's stages of change. The concepts of readiness and Three basic issues confront the clinician: patient-treatment matching apply not only (1) the type of exercise to prescribe, (2) to exercise in overweight persons, but also ways to maximize adherence, and (3) re- to dieting itself.11 lapse prevention. Table 2-5 outlines our rec- ommendations for exercise programs for Social Support overweight persons. Important elements are discussed below. All health behaviors, including exercise, are Influenced by social context. Attempts to Avoid a Threshold Mentality improve weight loss by involvingsignificant others have met with mixed results,133 per- Any activity, even those not normallyla- haps because of a failure to assess the needs beled as exercise, can provide substantial and characteristics of the target groups. One benefit. It is important to avoid the trap of defining physical activity in traditional terms (70% of maximal heart rate, three

44 Basic Concepts of Exercise Physiology Table 2-5. RECOMMENDATIONS FOR d. Use exercise following dietary lapses to MAXIMIZING EXERCISEADHERENCE IN psychologically regain a sense of control, OBESE PERSONS mastery, and commitment. General Principles e. Convey philosophy that a lapse can be used as a signal to re-initiate small amounts of physical 1. Be sensitive to psychologic barriers. activity (e.g., a 2-minute walk). Encourage 2. Be sensitive to physical barriers. notion that all exercise has a cumulative effect 3. Decrease focus on exercise threshold. on a number of domains (health, mood, senseof 4. Increase focus on enhanced self-efficacy. mastery). 5. Emphasize consistency and enjoyment, not f. Use of minimal intervention strategies, including amount and type. phone contacts, may foster exercise 6. Begin at a person's level of fitness. maintenance. 7. Encourage people to define routine activities as Source: Adapted from Grilo et al,26 p 266, with \"exercise.\" permission. 8. Focus on compliance and avoid emphasis on times per week, for at least 15minutes). This minor metabolic issues (e.g., whether to exercise three-part equation (frequency, intensity, before or after a meal). and duration) has been defined as essential 9. Consider life-span developmental context. for cardiorespiratoryconditioning,57 but it 10. Consider sociocultural issues and gender implies an exercise \"threshold\"—that is, influences. that exercise must occur in a specific 11. Evaluate social support network. amount to be beneficial. This threshold may 12. Evaluate stage of change and intervene motivate physically active or athletic per- accordingly. sons, but it may deter others, including the overweight. Since any exercise is worth- Specific Interventions while, the threshold mentality may hinder more than help. As a professional working 1. Prescription with overweight people, it is important for a. Provide clear information about importance of you to stress that low to moderatelevels of activity, including the psychologic benefits. exercise provide many health,79 psycho- b. Maximize routine activity. Define daily activities logic,96 and weight-loss benefits.52,120 Show- as exercise. ing overweight persons data such as Figure c. Maximize walking (e.g., walk while doing 2-6 can help make this point. errands). d. Increase use of stairs in lieu of escalators and Consistency May Be More elevators. Important than the Type or e. Incorporate a programmed activity that is Amount of Exercise enjoyable, fits with lifestyle, and is feasible as client's fitness improves. We believe the most important question to ask about exercise is, \"Will 1be doing this a 2. Behavioral year from now?\" It is important to help pa- a. Introduce self-monitoring, feedback, and goal- tients choose activities that will be enjoya- setting techniques. ble in the long run. Developing a consistent b. Identify important targets other than weight form of activity, or a consistent set of activ- loss, includingphysical changes, increased ities, is the primary focus. It is preferable to mobility (flexibility, endurance, ease), and have a person regularly play tennis twice a lowered heart rate. week and walk for one additional day than to c. Suggest that exercise may help soothe emotional run 4 miles/d for a week and then stop en- distress when risk for overeating is high. tirely. Lifestyle change, consistency, and d. Stimulus control: increase exercise cues (e.g., moderation are the keygoals. reminders for increasing activity) and decrease competing cues (e.g., do not schedule exercise when it might conflict with work or social obligations). 3. Maintenance and relapse prevention a. Use flexible guidelinesand goal-setting, but avoid rigid rules. b. Identify potential high-risksituations for skipping exercise (e.g., stressful times, busy schedule). c. Develop plans to cope with high-risk situations.

Exercise and Regulation of Body Weight 45 Provide Thorough Education for the increase in dieting and exercise be- It is important to emphasize that even havior.137 Consumers are frantically search- ing for information to achieve the perfect low-intensity exercise leads to enhanced di- body. One need only look at the multibillion etary adherence and weight control. Other- dollar industry to help people look more at- wise, people will feel they are always exer- tractive—diets, exercise paraphernalia, cising \"less than they should.\" Education cosmetics, fashions, and various forms of regarding the physical and psychologicben- cosmetic surgery—to realize the extent to efits of exercise can expand the patient's un- which there is societal pressure to \"look derstanding of the potential benefits. Dis- good.\"141 pelling erroneous notions such as \"no pain, no gain\" is an essential component. Poor Two beliefs fuel this search for the \"ideal\" health behaviors can result from inadequate body. The first belief is that the body is infi- information as well as nonadherence. nitely malleable,and that with the right diet, exercise program,and personal effort, an in- Be Sensitive to the Special dividual can achieve the aesthetic ideal. The Needs of Overweight Persons second belief is that once the ideal is achieved, there will be considerable re- Since obese persons have special psycho- wards, such as career advancement, wealth, logic and physical barriers to exercise, help- interpersonal attraction, and happiness.137 ing them feel comfortable with exercise and helping them define even low levels of activ- Ideal Versus Healthy Versus ity as exercise is an important step toward Reasonable Weight adherence. Simply conveying understand- ing and sensitivity can be helpful. The body cannot be shaped at will. Ge- netic factors play a substantial role in limit- SPECIAL ISSUES ing our ability to change body weight142,143 and body shape.144 Certain individuals may It is important to develop \"reasonable\" be prone to gain weight or to have specific weight-loss goals and healthy attitudes re- body shapes and these factors may resist at- garding exercise and diet. Our culture's pre- tempts to lose weight.11 This creates a mis- occupation with shape and weight may match between cultural pressures and bio- foster unhealthy attitudes. Health care pro- logicrealities.137 fessionals should be aware of methods to encourage the pursuit of \"reasonable\" This collision between cultural pressures weight-loss goals. and biologic realities leads to the critical question of how much control a person has The Role of Exercise In the over weight and shape.145 Scientists have es- Search for the Perfect Body timated that current aesthetic ideals (popu- lar models and actresses) have 10% to 15% Today's aesthetic ideal is becoming in- body fat, compared with 22% to 26% for creasingly lean,coupled with an added pres- healthy, normal-weight women.137,140,146 For sure to be physicallyfit.137–140The symbolic instance, a study by Wiseman and connotations of having the ideal body (suc- colleagues140 found that the majority of Play- cess, self-control, acceptance), current stan- boy centerfolds and Miss America contes- dards about ideal body weight and shape, tants were 15% or more below their ex- and the overstated health benefits of slen- pected weight, one of the criteria for derness are important factors responsible anorexia nervosa. One may speculate that many of our \"ideals\" have eating disorders. Miss America contestants work out an aver- age of 14 hours per week, with some ap-

46 Basic Concepts of Exercise Physiology preaching 35 hours.147Although the current weight, but a reasonable weight. Table 2-6 societal ideal is unattainable and/or unreal- lists questions to formulate a reasonable istic for most people, those who do not meet weight for an individual patient. The calcu- the ideal are often judged to be lazy, indul- lation of reasonable weight would take into gent, and lacking willpower. The exercise account the individual's weight history, de- and weight loss needed to pursue the aes- velopmental stage, social circumstances, thetic ideal, however, is far in excess ofwhat metabolic profile, and other factors. For in- is necessary (or recommended) for healthy stance, specific milestones, transitions, and living.146 life periods affect how women feel toward their bodies. Females begin life with more Weight-loss programs typically identify body fat than males, and this difference con- some \"goal weight\" or \"ideal weight\" as the tinues to increase during specific develop- desired outcome. Moreover, whether or not mental stages over the life span (at puberty, there are formal goals developed by pro- pregnancy, and menopause). These physi- gram staff, patients often have self-imposed ologic changes promote weight gain.148 Dis- goals influenced by visualizations of an aes- cussing these developmental transitions thetic ideal. The notion of ideal weight may can help women develop an acceptance and be useful for people who are only mildly understanding of the physiologic changes overweight (because the ideal is potentially while also using this information to formu- attainable), or for prevention efforts in late a reasonable weight goal. which excess weight beyond the standard signals the need for intervention. For many In some cases, reasonable weight and people, however, the ideal generates a health ideals may be the same (e.g., the in- search for an elusive goal, which often leads dividual can sustain the effort, calorie re- to poor long-term results. striction, and exercise necessary to main- tain that weight). On the other hand, the Brownell and Wadden11 suggest that it is reasonable weight might exceed the ideal important to think not only of an ideal weight if biologic, psychologic, develop- mental, or culturalvariables interfere. Table 2-6. QUESTIONS USED AS CLINICAL CRITERIA TO HELP ESTABLISH A Nonetheless, any weight loss is likely to \"REASONABLE WEIGHT\" FOR AN be beneficial, particularly if it can be main- INDIVIDUAL* tained. For some individuals, a small weight 1. Is there a history of excess weight in your parents loss can lead to significant improvements in medical conditions149,150 and may have a or grandparents? number of positive outcomes, such as feel- 2. What is the lowest weight you have maintained as ing more energetic, improved mobility, or less dependence on others for basic needs. an adult for at least one year? Thus, patients should be encouraged to set 3. What is the largest size of clothes that you feel goals according to several parameters, since this may help to prevent the commontrap of comfortable in, at the point you say \"I look pretty viewing anything but goal weight as failure. good considering where I have been\"? At what Tracking changes in physiologic factors that weight would you wear these clothes? are likely to change with increased physical 4. Think of a friend or family member (with your age activity and weight loss (e.g., blood sugar, and body frame) who looks \"normal\" to you. What blood pressure, serum cholesterol); anthro- does the person weigh? pometric measures (e.g., skinfold thickness 5. At what weight do you believe you can live with the and circumferences); and psychologic required changes in eating and/or exercise? changes may provide clear evidence of ac- *Thesequestions are based in part on criteria proposed complishment to both patients and health by Brownell and Rodin136 and represent clinical im- professionals. Maintaining these benefits pression. Research-based criteria have not been established. Source: Reprinted from Brownell and Wadden,11 p 509, with permission.

Exercise and Regulation of Body Weight 47 can be one central goal of treatment, even if males said that they were often, usually, or more weight is to be lost. always \"terrified of being fat.\" Exercise Overuse (Abuse) This \"terror of being fat\" can cause some As we have noted, exercise is an impor- individuals to fall into the trap of excessively exercising while still falling short of the tant aspect of weight control and is gener- \"perfect body.\" Many studies evaluate ally viewed as a healthy and positive en- whether people diet or exercise, but mini- deavor. Unfortunately, exercise can become mal attention has been paid to why they do compulsive when done in pursuit of exces- so. A substantial subset of runners may be sive thinness. An enduring fear of being fat motivated by the fear of beingfat and may be is a hallmark of anorexia nervosa and bu- running away from a vision of being fat.Be- limia nervosa.14,151–153 Vigorous exercise can cause both diet and exercise are excessive be a means of weight loss or one of several in some individuals, knowing the motivation tactics used by the individual to counteract may be helpful in detecting unhealthy exer- the ingestion of excess calories or deal with cise and dietary behaviors. Table 2-7 pre- body image concerns. Intense fears of be- sents questions that might aid health profes- coming fat may exist in people across all sionals in determining whether exercise is weight groups and body shapes. excessive or potentially problematic.158 These questions are based on our clinical Even exceptionally lean persons may experience and may not predict exercise have body image disparagement. In fact, a abuse. Rather, affirmative responses sug- growing body of research with athletes sug- gest the need for further evaluation and un- gests that a disproportionately high rate of derstanding of that individual's use (or po- fear of fatness and extreme dieting measures tential abuse) of exercise. It is critically may exist in these lean and fit individuals.19 One group of researchers investigated the Table 2-7. ASSESSMENT QUESTIONS TO functional role of exercise in a group of 112 SCREEN FOR POTENTIAL EXERCISE women who were regular exercise partici- ABUSE pants.154 While only a handful were over- 1. Are there times during the day when you feel weight, 77% of these relatively slender and active women wanted to lose weight, and unable to stop thinking about exercise, even if you most of them were dieting (57%). Another want to? study revealed that 19% of a group of female 2. Do you feel anxious, irritable, or uncomfortable runners met diagnostic criteria for bulimia when you miss an exercise session? nervosa,155 which is a much higher preva- 3. If you miss an exercise session, do you feel that you lence than expected in this group.156 Of the need to make up for it (e.g., by staying up later or bulimic women, most cited exercise as their getting up earlier to do it, by increasing the amount most common compensation tactic for of exercise you do the next day)? binge-eating episodes. Results did not indi- 4. Have you sometimes exercised despite being cate a particular weight or running profile advised against it (i.e., by a doctor, friend, family (that is, the bulimics were not significantly member)? What advice was given? Why did you different on mileage per week or fastest time exercise? for a 10-Krace than nonbulimics), but did 5. Do you try to increase your exercise session (or reveal associated psychologic factors (di- add an additional exercise) when you feel you have etary restraint and depression). A survey overeaten or when you eat \"junk foods\"? conducted in Runner's World magazine157 re- 6. Do you worry about putting on weight or becoming vealed that among the 4000 runners who re- fat if you miss an exercise session? sponded, 48% of the females and 21% of the 7. When you exercise, do you think about the calories or the amount of fat you are burning off? Source: From Grilo and Wilfley,158 p 163, with permission.

48 Basic Concepts of Exercise Physiology important for health professionals to rec- adolescents and adults: Youth risk behavior ognize possible signs and symptoms of ex- survey and behavioral risk factor surveil- ercise abuse. lance system. In Methods for Voluntary Weight Loss and Control. NIH Technology SUMMARY Assessment Conference, 1992, p 46. 5. Dishman RK: Increasing and maintaining Weight control is widely sought after by exercise and physical activity. Behav Ther women in the United States. This pervasive 22:345, 1991. desire for thinness leads women to seek out 6. Kuczmarski RJ: Prevalence of overweight many different combinations of diet and ex- and weight gain in the United States. Am J ercise programs. It is critical, therefore, to Clin Nutr 55:495S-502S,1992. understand the physiologic and psycho- 7. Bray GA: Effects of obesity on health and logic effects of such programs and to iden- happiness. In Brownell KD, and Foreyt JP tify programs that are safe and effective. (eds): Handbook of EatingDisorders: Phys- iology, Psychology, and Treatment of Obe- Physical activity is central to this en- sity, Anorexia, and Bulimia. New York, Basic deavor. It is the most powerful predictor of Books 3, 1986. long-term weight maintenance. Exercise 8. Pi-Sunyer FX: Health implications of obe- programs of low to moderate intensity have sity. Am J Clin Nutr 53:1595S,1991. superior adherence to those of high inten- 9. National Institutes of Health Consensus De- sity and have many health, psychologic, and velopment Panel on the HealthImplications weight-loss benefits. We feel it is critical to of Obesity: Health implications of obesity. encourage overweight and inactive women National Institutes of Health consensus de- to view any activity as beneficial and that velopment conference statement. Ann In- consistency is the key variable. tern Med 103:1073,1985. 10. Bray GA: Pathophysiology of obesity. Am J Conversely, it is important to recognize Clin Nutr 55:488S,1992. possible signs of exercise abuse. Sadly, 11. BrownellKD, and Wadden, TA: Etiology and many women are in pursuit of the current treatment of obesity: Toward understanding societal ideal, which is often unattainable a serious, prevalent, and refractory disor- and/or unrealistic. Women should be en- der. J Consult Clin Psychol 60:505, 1992. couraged to develop reasonable expecta- 12. Pyle RL, Mitchell JE, Eckert ED, et al: Main- tions for weight control and exercise. Focus tenance treatment and 6-monthoutcome for on lifestyle change, consistency, and mod- bulimic patients who respond to initial eration may be the best treatment philoso- treatment. Am J Psychiatry 147:871,1990. phy. 13. Pike KM,and Rodin J: Mothers, daughters, and disordered eating. J Abnorm Psychol REFERENCES 100:198, 1991. 1. Begley CE: Government should strengthen 14. Striegel-Moore RH, Silberstein LR, and regulation in the weight loss industry. J Am Rodin J: Toward an understanding of risk Diet Assoc 91:1255, 1991. factors for bulimia. Am Psychol 41:246, 2. Centers for Disease Control: Body-weight 1986. perceptions and selected weight-manage- 15. Striegel-Moore RH, Silberstein LR, and ment goals and practices of high school stu- Rodin J: The social self in bulimia nervosa: dents—United States, 1990. MMWR 40:741, Public self-consciousness, social anxiety, 1991. and perceived fraudulence. J Abnorm Psy- 3. Kolbe LJ: An epidemiological surveillance chol (in press). system to monitor the prevalence of youth 16. Wilson, GT: Short-term psychological ben- behaviors that most affect health. Health efits and adverse effects of weight loss. In Educ 21:44, 1990. Methods for Voluntary Weight Loss and 4. Serdula M: Weight control practices in U.S. Control NIH Technology Assessment Con- ference, 1992, p 134. 17. Rand CSW, and Kuldau, JM: The epidemiol- ogy of obesity and self-defined weight prob- lem in the general population. Int J Eat Dis 9:329, 1990. 18. Hsu G: Eating Disorders. Guilford Press, New York, 1990. 19. Brownell KD,Rodin J, and WilmoreJH: Eat-

Exercise and Regulation of Body Weight 49 ing, Body Weight and Performance in Ath- Valoski A: Five-year follow-up of family- letes. Lea and Febiger, Philadelphia, 1992. based behavioral treatments for childhood 20. Brownell KD,and Wadden, TA: The hetero- obesity. J Consult Clin Psychol 58:661,1990. geneity of obesity: Fitting treatments to in- 34. Hill JO, Schlundt DG,Sbrocco T, et al: Eval- dividuals. Behav Ther 22:153, 1991. uation of an alternating-calorie diet with 21. Van Itallie TB: Health implications of over- and without exercise in the treatment of weight and obesity in the United States.Ann obesity. Am J Clin Nutr 50:248, 1989. Intern Med 103:983,1985. 35. Kayman S, Bruvold W, and Stern JS: Main- 22. U.S.Department of Agriculture: Nationwide tenance and relapse after weight loss in food consumption survey. Nutrient intakes, women. Behavioral aspects. Am J Clin Nutr individuals in 48 years, year 1977-1978, Re- 52:800, 1990. port No. 1-2, Consumer Nutrition Division, 36. King, AC, Frey-Hewitt B, Dreon DM, and Human Nutrition Information Service. 1984. Wood PD: Diet versus exercise in weight Hyattsville, MD. maintenance: The effects of minimal inter- 23. McGinnis JM: The public health burden of a vention strategies on long-term outcomes in sedentary lifestyle. Med Sci Sports Exerc men. Arch Intern Med 149:2741,1989. 24:S196,1992. 37. Sikand G, Kondo A, Foreyt JP, Jones PH, and 24. Centers for Disease Control: Sex-, age-, and Gotto AM: Two-year follow-up of patients region-specific prevalance for sedentary treated with a very-low-calorie-diet and ex- lifestyle in selected states in 1985—The Be- ercise training. Am Diet Assoc 88:487,1988. havioral Risk Factor Surveillance System. 38. ColvinRH, and Olson SB: A descriptive anal- MMWR 36:195, 1987. ysis of men and women who have lost sig- 25. Centers for Disease Control: CDC surveil- nificant weight and are highly successful at lance summaries. MMWR 39(No. SS-2):8, maintaining the loss. Addict Behav 8:287, 1990. 1983. 26. Grilo CM, Brownell KD, and Stunkard AJ: 39. Gormally J, Rardin D, and Black S: Corre- The metabolic and psychological impor- lates of successful response to a behavioral tance of exercise in weight control. In Stun- weight control clinic. J Counsel Psychol kard AJ, and Wadden T (eds): Obesity: The- 27:179, 1980. ory and Therapy, ed 2. Raven Press, New 40. Gormally J, and Rardin D: Weight loss and York, 1993, pp 253-273. maintenance changes in diet and exercise 27. Klesges RC, Eck LH, Isbell TR, et al: Physical for behavioral counseling and nutrition ed- activity, body composition, and blood pres- ucation. J Consult Clin Psychol 28:295,1981. sure: A multimethod approach. Med Sci 41. Marston AR, and Criss J: Maintenance of Sports Exerc 23:759, 1991. successful weight loss: Incidence and pre- 28. Strazzulo P, Cappuccio M, Trevisan M, et al: diction. Int J Obes 8:435, 1984. Leisure time physical activity and blood 42. Dahlkoetter J, Callahan EJ, and Linton J: pressure in schoolchildren. Am JEpidemiol Obesity and the unbalanced energy equa- 127:726, 1988. tion: Exercise vs. eating habit change. JCon- 29. Pavlou KN, Krey S, and Steffee WP: Exercise sult Clin Psychol 47:898, 1979. as an adjunct to weight loss and mainte- 43. Duddleston AK, and Bennion M: Effect of nance in moderately obese subjects. Am J diet and/or exercise on obese college Clin Nutr 49:1115,1989. women: Weight loss and serum lipids. J Am 30. King AC, Taylor CB, and Haskell WL: Ex- Diet Assoc 56:126, 1970. panding methods for achieving sustained 44. Harris MB, and Hallbauer ES: Self-directed participation in community-based physical weight control through eating and exercise. activity. The First International Congress of Behav Res Ther 11:523,1973. Behavioral Medicine, Upsala, Sweden. In- 45. Stalonas PM, Johnson WG, and ChristM:Be- ternational Society of Behavioral Medicine, havior modification for obesity: The evalu- 1990. ation of exercise, contingency management, 31. Perri MG, McAdooWG, McAllister DA,et al: and program adherence. J Consult Clin Psy- Enhancing the efficacy of behavior therapy chol 46:463, 1978. for obesity: Effects of aerobic exercise and a 46. Van Dale D, and Saris WHM: Repetitive multicomponent maintenance program. J weight loss and weight regain: Effects on Consult Clin Psychol 54:670,1986. weight reduction, resting metabolic rate, 32. Craighead LW, and Blum MD: Supervised and lipolytic activity before and after exer- exercise in behavioral treatment for mod- cise and/or diet treatment. Am J Clin Nutr erate obesity. Behav Ther 20:49,1989. 49:409,1989. 33. Epstein LH, McCurley J, Wing RR, and 47. Belko AZ, Van Loan M, Barbieri TF, and

50 Basic Concepts of Exercise Physiology Maclin P: Diet, exercise, weight loss, and energy expenditure in moderately over- 62. Welle SL, Amatruda JM, Forbes GB, and weight men. Int J Obes 11:93,1987. Lockwood DH: Resting metabolic rates of obese women after rapid weight loss. J Clin 48. Lennon D, Nagle F, Stratman F, Shrago E, Endocrinol Metab 59:41,1984. and Dennis S: Diet and exercise training ef- fects on resting metabolic rate: Int J Obes 63. Brownell KD, and Grilo CM: Weight manage- 9:39,1985. ment. In Durstine JL and Robertson M (eds): Resource Manual for Guidelines for 49. Phinney SD, La Grange BM, O'Connell M, Exercise Testing and Prescription, 1993, p and Danforth E: Effects of aerobic exercise 455. on energy expenditure and nitrogen bal- ance during very low calorie dieting. Metab- 64. Tremblay A, Despres JP, and Bouchard C: olism 37:758, 1988. The effects of exercise-training on energy balance and adipose tissue morphology and 50. Hill JO, Newby FD, Thacker SV, Sykes MN, metabolism. Sports Med 2:223, 1985. and Di Girolamo M: Influence of food restric- tion coupled with weight cycling on carcass 65. Tremblay A, Fontaine E, Poehlman ET, et al: energy restoration during ad libitumrefeed- The effect of exercise-training on resting ing. Int J Obes 12:547, 1988. metabolic rate in lean and moderately obese individuals. Int J Obes 10:511, 1986. 51. Epstein LH, Koeske R, and Wing RR: Adher- ence to exercise in obese children. J Cardiac 66. Broeder CE, Burrhus KA, Svanevik LS, and Rehab 4:185, 1984. Wilmore JH: The effects of either high-inten- sity resistance or endurance training on 52. Epstein LH, Wing RR, Koeske R, Ossip DJ, resting metabolic rate. Am J Clin Nutr and Beck S:A comparison of lifestyle change 55:802, 1992. and programmed aerobic exercise on weight and fitness changes in obese chil- 67. Anderson B, Xu X, Rebuffe-Scrive M, et al: dren. BehavTher 13:651,1982. The effects of exercise training on body composition and metabolism in men and 53. Brownell KD, Stunkard AJ, and Albaum JM: women. Int J Obes 15:75, 1991. Evaluation and modification of exercise pat- terns in the natural environment. Am J Psy- 68. Epstein LH, Wing RR, and Thompson JK: chiatry 137:1540, 1980. The relationship between exercise inten- sity, caloric intake, and weight. Addict 54. Bjorntorp P: Exercise and obesity. Psychiatr Behav 3:185, 1978. Clin North Am 1:691, 1978. 69. Holm G, Bjorntorp P, and Jagenberg R:Car- 55. Bray G: The obese patient. WB Saunders, bohydrate, lipid, and amino acid metabo- Philadelphia, 1976. lism following physical exercise in man. J ApplPhysiol 45:128, 1978. 56. Danforth E, and Landsberg L: Energy expen- diture and its regulation. In Greenwood 70. Woo R, Garrow JS, and Sunyer FXP: Effect of MRC (ed): Obesity. New York, ChurchillLiv- exercise on spontaneous calorie intake in ingstone, 1983, p 103. obesity. Am J Clin Nutr 36:470,1982. 57. McArdleWD, Katch FI, and Katch VL:Exer- 71. Woo R, and Pi-Sunyer FX:Effect of increased cise Physiology: Energy, Nutrition, and physical activity on voluntary intake in lean Human Performance. Lea and Febiger, Phil- women. Metabolism 34:836,1985. adelphia, 1991. 72. Reed DR, Contreras RJ, Maggio C, Green- 58. Barrows K, and Snook JT: Effect of a high- wood MRC, and Rodin J: Weight cycling in protein, very-low-calorie diet on resting me- female rats increases dietary fat selection tabolism, thyroid hormones, and energy ex- and adiposity. Physiol Behav 42:389,1988. penditure of obese middle-aged women.Am J Clin Nutr 45:391,1987. 73. Gerardo-Gettens T, Miller GD, Horwitz BA, et al: Exercise decreases fat selection in fe- 59. Elliot DL,Goldberg L, Kuehl KS, and Bennett male rats during weight cycling. Am J Phys- WM: Sustained depression of resting meta- iol 260:R518,1991. bolic rate after massive weight loss. Am J Clin Nutr 49:93, 1989. 74. Bailor DL, McCarthyJP, and Wilterdink EJ: Exercise intensity does not affect the com- 60. Mole PA, Stern JS, Schultz CL, Bernaver EM, position of diet- and exercise-induced body and Holcomb, BJ: Exercise reverses de- mass loss. Am J Clin Nutr 51:142,1990. pressed metabolic rate produced by severe caloric restriction. Med Sci Sports Exerc 75. Bouchard C, Tremblay A, Despres J-P, et al: 21:29, 1989. The response to long-term overfeeding in identical twins. N Engl J Med 322:1477,1990. 61. Ravussin E, Burnand B, Schutz Y, and Jequier E: Energy expenditure before and 76. Deprés J-P, Bouchard C,Tremblay A, Savard during energy restriction in obese patients. R, and Marcotte M: Effects of aerobic train- Am J Clin Nutr 41:753,1985. ing on fat distribution in male subjects. Med Sci Sports Exerc 17:113,1985.

Exercise and Regulation of Body Weight 51 77. Segal KR, and Pi-Sunyer FX: Exercise, rest- in 38-year-old European men: The European ing metabolic rate, and therrnogenesis. Di- Fat Distribution Study. Am J Epidemiol abet Metabol Rev 2:19,1986. 133:257,1991. 92. Tremblay A, Després J-P, Leblanc C, et al: Ef- 78. Donnelly JE, Pronk NP, Jacobsen DJ, Pronk fect of intensity of physical activity on body SJ, Jakicic JM: Effects of a very-low-calorie fatness and fat distribution. Am J Clin Nutr diet and physical-training regimens on 51:153, 1990. body composition and resting metabolic 93. Troisi RJ, Heinold JW, Vokonas PS, and rate in obese females. Am J Clin Nutr 54:56, Weiss ST:Cigarette smoking, dietary intake, 1991. and physical activity: Effects on body fat dis- tribution—the Normative Aging Study. AmJ 79. Blair SN, Kohl HW, Paffenbarger RS, Clark Clin Nutr 53:1104,1991. DG, Cooper KH, and Gibbons LW: Physical 94. Wing RR, Matthews KA, Kuller LH,Meilahn fitness and all-cause mortality. J Am Med EN, and Plantinga A: Waist to hip ratio in Assoc 262:2395, 1989. middle-aged women: Associations with be- havioral and psychosocial factors and with 80. Helmrich SP, et al: Physical activity and re- changes in cardiovascular risk factors. Ar- duced occurrence of noninsulin-dependent teriosclerosis Thrombosis 11:1250,1991. diabetes mellitus. N Engl J Med 325:147, 95. Plante TG,and Rodin J: Physical fitness and 1991. enhanced psychological health. Curr Psy- chol: Res Rev 9:3,1990. 81. Manson JE, Colditz GA, Stampfer MJ, et al: 96. Rodin J, and Plante TG: The psychological Physical activity and incidence of non-in- effects of exercise. In Williams RS, and Wal- sulin-dependent-diabetes mellitus in lace A (eds): Biological Effects of Physical women. Lancet 338:774, 1991. Activity. Human Kinetics Books. Cham- paign, IL, 1989, p 127. 82. Paffenbarger RS, Hyde RT, Wing AL, and 97. Grilo CM, Shiftman S, and Wing RR: Relapse Hsieh CC: Physical activity, all-cause mor- crises and coping among dieters. J Consult tality, and longevity of college alumni. N Clin Psychol 57:488, 1989. Engl J Med 314:605, 1986. 98. Doyne EJ, Ossip-Klein DJ, Bowman ED, Os- born KM et al: Running versus weight lifting 83. Dubbert PM: Exercise in behavioral medi- in the treatment of depression. J Consult cine. J Consult Clin Psychol 60:613, 1992. Clin Psychol 55:748, 1987. 99. King AC, Taylor CB, Haskell WL, and 84. Hanson DF, and Nedde WH: Long-term De Busk RF: Influence of regular aerobic ex- physical training effect in sedentary fe- ercise on psychological health: A random- males. J Appl Physiol 37:112, 1978. ized, controlled trial of healthy middle-aged adults. Health Psychol 8:305, 1989. 85. DeBusk RF, Stenestrand U, Sheehan M, and 100. Martinsen EW,Medhus A, and Sandvik L: Ef- Haskell HL: Training effects of long versus fects of aerobic exercise on depression: A short bouts of exercise in healthy subjects. controlled study. Br Med J 291:109,1985. Am J Cardiol 65:1010, 1990. 101. Martinsen EW, Strand J, Paulsson G, and Kaggestad J: Physical fitness level in pa- 86. Leon AS, Connett J, Jacobs DR, Rauramaa R: tients with anxiety and depressive disor- Leisure-time physical activity levels and ders. Int J Sports Med 10:58,1989. risk of coronary heart disease and death. 102. Steptoe A, and Cox S: Acute effect of aerobic JAMA 258:2388, 1987. exercise on mood. Health Psychol 7:329, 1988. 87. Lee C: Women and aerobic exercise: Direc- 103. Sallis JF, and Hovell MF:Determinants of ex- tions for research development. Ann Behav ercise behavior. In Pandolf KB, and Hol- Med 13:133, 1991. loszy JO (eds): Exercise and Sport Sciences Reviews, vol 18. Williams & Wilkins, Balti- 88. Powell, Caspersen CJ, Koplan JP, and Ford more, 1990, p 307. ES: Physical activity and chronic disease. 104. Ernst ND,and Harlan, WR: Obesity and car- Am J Clin Nutr 49:999,1989. diovascular disease in minority popula- tions: Executive summary. Conferencehigh- 89. Wood PD, Stefanick ML, Dreon DM, et al: lights, conclusions, and recommendations. Changes in plasma lipids and lipoproteins Am J Clin Nutr 53:1507S, 1991. in overweight men during weight loss 105. Pawson IG, Martorell R, and Mendoza F: through dieting as compared with exercise. N Engl J Med 319:1173, 1988. 90. Lapidus L, Bengtsson C, Larsson B, Pennert K, Rybo E, and Sjostrom L: Distribution of adipose tissue and risk of cardiovascular disease and death: 12 year follow-up of par- ticipants in the population study of women in Gothenburg, Sweden. Br Med J 289:1261, 1984. 91. Seidell JC, Cigolini M, Després J-P, Char- zewski J, et al: Body fat distribution in rela- tion to physical activity and smoking habits

52 Basic Concepts of Exercise Physiology Prevalence of overweight and obesity in 121. Brownell KD,and Stunkard AJ: Physical ac- U.S. Hispanic populations. Am J Clin Nutr tivity in the development and control in 53:1522S, 1991. obesity. In Stunkard AJ (ed): Obesity. WB 106. Sobal J, and Stunkard AJ: Socioeconomic Saunders, Philadelphia, 1980, p 300. status and obesity: A review of the litera- ture. Psychol Bull 105:260,1989. 122. King AC, Haskell WL, Taylor CB, et al: 107. WilliamsonDF, Kahn HS, Remington PL, and Group- vs home-based exercise training in Anda RF: The 10-year incidence of over- healthy older men and women: A commu- weight and major weight gain in U.S. adults. nity-based clinical trial. JAMA 266:1535, Arch Intern Med 150:665,1990. 1991. 108. Caspersen CJ, Christenson GM,and Pollard RA: Status of the 1990 physical fitness and 123. Marlatt GA, and Gordon J (eds): Relapse exercise objectives-evidence from NHIS. Prevention: Maintenance Strategies in the Public Health Rep 101:587,1986. Treatment of Addictive Behaviors. New 109. Thompson JK: Body image disturbance: As- York, Guilford Press, 1985. sessment and treatment. Pergamon, Elms- ford, NY, 1990. 124. Baum JG, Clark HB, and Sandier J: Prevent- 110. Thompson JK, Fabian LJ, Moulton DO, Dunn ing relapse in obesity through posttreat- ME, and Altabe MN: Development and vali- ment maintenance systems: Comparing the dation of the physical appearance related relative efficacy of two levels of therapist teasing scale. J Pers Assess 56:513,1991. support. J Behav Med 14:287,1991. 111. Allon N: The stigma of overweight in every- day life. In Wolman B (ed): Psychological 125. Belisle M, Roskies E, and Levesque MM:Im- Aspects of Obesity: A Handbook. Van Nos- proving adherence to physical activity. trand Reinhold, New York, 1982, p 130. Health Psychol 6:159, 1987. 112. Wadden TA, and Stunkard AJ: Social and psychological consequences of obesity. Ann 126. King AC, and Frederiksen LW: Low-cost Int Med 103:1062, 1985. strategies for increasing exercise behavior: 113. King A: Community intervention for pro- Relapse preparation trainingand social sup- motion of physical activity and fitness. In port. Behav Modif 8:3,1984. Pandolf KB, and Holloszy JO (eds): Exercise and Sport Sciences Reviews, vol 19. Wil- 127. King AC,Taylor CB, HaskellWL,and DeBusk liams &Wilkins, Baltimore, 1991, p 211. RF: Strategies for increasing early adher- 114. Dubbert PM, and Martin JM: Exercise. In ence to and long-term maintenance of Blechman EA, and Brownell KD (eds): home-based exercise training in healthy Handbook of Behavioral Medicine for middle-aged men and women. Am J Cardiol Women. Pergamon, New York, 1988, p 291. 61:628, 1988. 115. Gwinup G: Effect of exercise alone on the weight of obese women. Arch Int Med 128. Martin JE, Dubbert P, Katell AD, et al: Be- 135:676,1975. havioral control of exercise in sedentary 116. Sallis JF, Haskell WL, Fortmann SP, adults: Studies 1 through 6. J Consult Clin Vranizun KM, Taylor CB, and Solomon DS: Psychol 52:795, 1984. Predictors of adoption and maintenance of physical activity in a community sample. 129. Marcus BH, Rossi JS, Selby VC, et al: The Prev Med 15:331,1986. stages and process of exercise adoption and 117. Dishman RK, Sallis JF, and Orenstein DR: maintenance in a worksite sample. Health The determinants of physical activity and Psychol, in press. exercise. Public Health Rep 100:158, 1985. 118. Sallis JF, Haskell WL, Wood PD, et al: Phys- 130. Prochaska JO, Harlow LL,ReddingCA,et al: ical activity assessment methodology in the Stages of change, self-efficacy, and deci- Five-City Project. Am J Epidemiol 121:91, sional balance of condom use in a high HIV- 1985. risk sample. Am J Commun Psychol, in 119. Foster VL, Hume GJ, Byrnes WC, et al: En- press. durance training for elderly women: Mod- erate vs low intensity. J Gerontol 44:M184, 131. DiClementeCC, Prochaska JO, FairhurstSK, 1989. et al: The process of smoking cessation: An 120. Epstein LH,Wing RR, Koeske R, and Valoski analysis of precontemplation, contempla- A: A comparison of lifestyle exercise, aero- tion and preparation stages of change. J bic exercise, and calisthenics on weight loss Consult Clin Psychol 59:2953,1991. in obese children. Behav Ther 16:345, 1985. 132. Fowler JL, Follick MT, Abrams DB,and Rick- ard-Figueroa K: Participant characteristics as predictors of attrition in worksite weight loss. Addict Behav 10:445, 1985. 133. Black DR, Gleser LJ, and Kooyers KJ: A meta-analytic evaluation of couples' weight- loss program. Health Psychol 9:330,1990. 134. Wing RR, Marcus MD, Epstein LH, and Jawad A: A \"family-based\" approach to the treatment of obese type II diabetic patients. J Consult Clin Psychol 59:156, 1991.

Exercise and Regulation of Body Weight 53 135. Brownell KD: The LEARN program for vosa: A multidimensional perspective. weight control. American Health Publishing Brunner/Mazel, New York, 1982. Company, Dallas, 1991. 153. Wilson GT: Bulimia nervosa: Models, as- sessment, and treatment. Curr Opinion Psy- 136. Brownell KD, and Rodin J: The weight main- chiatry 2:790,1989. tenance survival guide. American Health 154. Davis C, Fox J, Cowles M, Hastings P, and Publishing Company, Dallas, 1990. Schwass K: The functional role of exercise in the development of weight and diet con- 137. Brownell KD: Dieting and the search for the cerns in women. J Psychosom Res 34:563, perfect body: Where physiology and culture 1990. collide. BehavTher 22:1,1991. 155. Prussin RA, and Harvey PD: Depression, di- etary restraint, and binge eating in female 138. Freedman R: Beauty Bound. Lexington runners. Addict Behav 16:295,1991. Books, Lexington, MA, 1986. 156. Pope HG,Jr, Hudson JI, and Yurgelen-Todd D: Anorexia nervosa and bulimia among 300 139. Rodin J: Body Traps, Morrow, New York, women shoppers. Am J Psychiatry 141:292, 1992. 1984. 157. Brownell KD, Rodin J, and Wilmore JH: Eat, 140. Wiseman CV, Gray JJ, Mosimann JE, and drink, and be worried? Runner's World 28, Ahrens AH: Cultural expectations of thin- August 1988, p 28-34. ness in women: An update. Int J Eat Dis 158. Grilo CM, and Wilfley DE: Weight control: 11:85,1992. Exercise adherence and abuse. WeightCon- trol Digest 2:161, 1992. 141. Rodin J: Cultural and psychosocial deter- 159. Adams GM, and DeVries HA: Physiological minants of weight concerns. In Methods for effects of an exercise training regimen upon Voluntary Weight Loss and Control. NIH women aged 52 to 79. J Gerontol 28:50, Technology Assessment Conference 1992, p 1973. 17. 160. Badenhop DT, Cleary PA, et al: Physiologi- cal adjustments to higher- or lower-inten- 142. Stunkard AJ, Foch TT, and Hrubec Z: A twin sity exercise in elders. Med Sci Sports Exerc study of human obesity. JAMA 256:51,1986. 15:496, 1983. 161. Bassey EJ, Patrick JM, Irving JM, Blecher A, 143. Stunkard AJ, Harris JR, Pedersen NL, and Fenten PH: An unsupervised \"aerobics\" McClearn GE: The body mass index of physical training programme in middle- twins who have been reared apart. N Engl aged factory workers: Feasibility, validation JMed 322:1483,1990. and responses. Eur J Appl Physiol 52:120, 1983. 144. Bouchard C, and Johnson FE (eds): Fat dis- 162. Blumenthal JA, Schocker DD, Needels TL, tribution during growth and later health and Hindle P: Psychological and physiolog- outcomes. Alan Liss, New York, 1988. ical effects of physical conditioning on the elderly. J Psychosom Res 26:505, 1982. 145. Brownell KD: Personal responsibility and 163. Blumenthal JA, Emery CF, Madden DJ, et al: control over our health: When expectation Cardiovascular and behavioral effects of exceeds reality. Health Psychol 10:303, aerobic exercise training in healthy older 1991. men and women. J Gerontol 44:M147, 1989. 164. Cavanaugh DJ, and Cann CE: Brisk walking 146. Katch FI, and McArdle WD: Nutrition, does not stop bone loss in postmenopausal Weight Control and Exercise, ed 3. Lea and women. Bone 9:201,1988. Febiger, Philadelphia, 1988. 165. Cowan MM, and Gregory LW: Responses of pre- and post-menopausal females to aero- 147. Trebbe A: Ideal is body beautiful and clean bic conditioning. Med Sci Sports Exerc cut. USAToday, September 15, 1979, p 1. 17:138, 1985. 166. Franklin B, Buskirk E, Hodgson J, et al: Ef- 148. Rodin J, and Larson L:Social factors and the fects of physical conditioning on cardiore- ideal body shape. In Brownell KD, Rodin J, spiratory function, body composition and and Wilmore JH (eds): Eating, Body Weight serum lipids in relatively normal-weight and Performance in Athletes. Lea and Febi- and obese middle-aged women. Int J Obes ger, Philadelphia, 1992, p 146. 3:97, 1979. 167. Getchell LH, and Moore JC: Physical train- 149. Blackburn GL, and Kanders BS: Medical ing: Comparative response of middle-aged evaluation and treatment of the obese pa- tient with cardiovascular disease. Am J Car- diol 60:55g, 1987. 150. Wassertheil-Smoller SW, Blaufox MD, Oberman A, Langford HG, and Davis BR: TAIM Study: Adequate weight loss as effec- tive as drug therapy for mild hypertension. Paper presented at American Heart Asso- ciation Conference on Cardiovascular Dis- ease Epidemiology, San Diego, 1990. 151. Fairburn CG, and Cooper, PJ: The clinical features of bulimia nervosa. Br J Psychiatry 144:238, 1984. 152. Garfinkel PE, and Garner DM:Anorexia ner-

54 Basic Concepts of Exercise Physiology adults. Arch Physical Med Rehab 56:250, 175. Netz Y, Tenenbaum G, and Sagir M: Patterns 1975. of psychological fitness as related to pat- 168. Haber P, Honiger B, Kilicpera M, and Nied- terns of physical fitness among older adults. erberger M: Effects on elderly people 67-76 Percept Motor Skills 67:647, 1988. years of age of three-month endurance training on bicycle ergometer. Eur Heart J 176. Seals DR, Hagberg JM, Hurley BF, Ehsani 5:37,1984. AA, and Holloszy JO: Endurance training in 169. Jarvie GJ, and Thompson, JK: Appropriate older men and women I. Cardiovascular re- use of stationary exercycles in the natural sponse to exercise. J Appl Physiol 57:1024, environment: The failure of instructions and 1984. goal setting to appreciably modify exercise patterns. Behav Ther 8:187,1985. 177. White MK, Yeater RA, Martin RB, et al: Ef- 170. Jette M, Sidney K,and Campbell J: Effects of fects of aerobic dancing and walking on car- a twelve-week program on maximal and diovascular function and muscular strength submaximal work output indices in seden- in post-menopausal women. J Sports Med tary middle-aged men and women. J Sports 24:159, 1984. Med Physical Fitness 28:59,1988. 171. Juneau M, Rogers F, DeSantos V, et al: Effec- 178. MacKeen PC, Franklin BA, Nicholas C, and tiveness of self-monitored, home-based, Buskirk ER: Body composition, physical moderate-intensity exercise training inmid- work capacity and physical activity habits at dle-aged men and women. Am J Cardiol 18-months follow-up of middle-agedwomen 60:66,1987. participating in an exercise intervention 172. Kukkonen K, Rauramaa R, Siitonen U, and program. Int J Obes 7:61, 1983. Hanninen O: Physical training of obese mid- dle-aged persons. Ann Clin Res 14:80,1982. 179. BlumenthalJA, Emery CF, Madden DJ, et al: 173. Lewis S, Haskell WL, Wood PD, et al: Effects Long-term effects of exercise on psycholog- of physical activity on weight reduction in ical functioning in older men and women. J obese middle-aged women. Am J Clin Nutr Gerontol, in press. 29:151,1976. 174. Morrison DA, Boyden TW, Pamenter RW, et ACKNOWLEDGMENTS al: Effects of aerobic trainingon exercise tol- We are grateful to Adele Jones for her as- erance and echocardiographic dimensions in untrained postmenopausal women. Am sistance with the preparation of this manu- Heart J 112:561,1986. script.

APPENDIX 2-1 Research Examining Physiologic Effects o Subject and Program Characteristics Subjects Authors N Age Notes Session Adams and DeVries159 Badenhop et al.160 Time (min) Bassey et al.161 Blumenthal et al.162 23 52-79 17 ex 40 Blumenthal et al.163 32 >60 6 control 50 Cavanaugh and Cann164 Cowan and Gregory165 26 F, 8 M Franklin et al.166 Foster et al.119 14 mod ex Getchell and Moore167 14 low ex 4 control 108 55-60 53 F 20-40 55 M 24 65-85 18 F 6M 30 101 60-83 51 F, 50 M 60 33 aerobic 34 yoga control 34 wait list control 17 m = 56 8 ex 25-50 9 control 38 35-66 20 pre-menopause 50 18 post-menopause 36 29-47 23 obese 45 13 normal 16 67-89 9 mod ex 17-42 9 low ex 23 28-57 11 F 30 12 M

of Exercise in Adult Women: Program Freq/ Intensity Weeks' Control Group Week Duration 60% MHR Last six to volunteer 3 60%-75% MHR 13 Those unable to commit time 3 30%-45% MHR 9 5? 12 Randomly assigned to successive programs 3 70%-85% MHR 11 None 3 70% MHR 16 Random 3 60% MHR 52 Those unable to commit time 4 80% MHR 9 Randomly assigned to ex or control 4 75% Vo2max 12 None 5 60% MHR 10 None 40% MHR 3-4 75%-85% MHR 10 None

APPENDIX 2-1 Research Examining Physiologic Effects of Subject and Program Characteristics (Con Subjects Authors N Age Notes Session Time (min) Haber et al.168 12 67-76 8F 20-40 25 Jarvie and Thompson169 16 26-52 4M 30 50 12 F 30-60 25 and 60 Jette et al.170 26 35-53 4M 40 12 F 60 30 and 60 Juneau et al.171 120 40-60 14 M 33 60 F Kukkonen et al.172 169 35-50 60 M 97 F Lewis et al.173 22 30-52 72 M Morrison et al.174 32 m = 51 22 ex Netz et al.175 24 50-64 10 control 13 F 11 M Seals et al.176 24 60-69 14 ex White et al.177 72 50-63 10 control 36 walk 36 dance *Subjects spent 24 weeks in low-intensity activity and then 24 weeks in higher-inte MHR = age-adjusted maximal heart rate; Vo2max = maximal oxygen capacity. Source: Adapted from Lee,87 p 134, with permission.

f Exercise in AdultWomen: ntinued) Program Freq/ Intensity Weeks' Week Duration Control Group 3 60% MHR 12 None 7 17 3 pulse? 12 Wait list 5 24 3-6 60% Vo2max 68 Random 50%in no-ex gp 2 and 2 17 3 65%-77% MHR 32 Random 50% in no-ex gp 3 12 3 60%-70% MHR 48* None 4 24 80% MHR and low None 65%-75% MHR Random 70% MHR None 40% MHR and Assignment method not 85% MHR specified 70% MHR None ensity.

APPENDIX 2-2 Outcomes of Studies Listed in Appendix 2 Authors Program Type % Im Adams and DeVries159 Supervised Drop Out PW Badenhop et al.160 Supervised 0 Vo Bassey et al.161 Home-based O2 0 RH 53 W PW Vo EH ph Blumenthal et al.162 Supervised 8 PW En Blumenthaletal.163 Supervised 4 Vo RH Cavanaugh and Cann164 Supervised Cowan and Gregory165 En Supervised? (not Foster et al.119 specifically stated) An To Supervised 0 RH Ph 0 %f V\" En 24 Vo PW

2-1 Physical Outcomes mproved No Change Follow-up None WC RSBP o2max RDBP None 2 pulse Skinfolds 12-week follow-up of 29 HR Weight Ss—some WC, EHR maintenance o2max None HR hys. activity Blumenthal et al.179 WC RSBP, RDBP None ndurance RHR, EHR None Weight o2max Bone density None HR Grip strength ndurance naerobic threshold Bone density otal cholesterol, LDL %fat HR Weight hys. activity Lean mass fat \"o2max Weight ndurance Blood lactate o2max EHR WC Total cholesterol HDL

APPENDIX 2-2 Outcomes of Studies Listed in Appendix 2- Authors Program Type % Im Drop Out Franklin etal.166 Supervised 0 EH We Getchell and Moore167 Supervised? (not Ski specifically stated) %f Haber et al.168 ESB Jarvie and Thompson169 Supervised RSB Home-based ( EH Ski Vo2 Lac 0 PW Ma Vo2 75 Jette et al. (1970) Supervised 0 Vo2 Juneau et al.171 Home-based EHR Kukkonen et al.172 Home-based 6 Vo2 Wei 44 Wei BM Vo2 RSB Seru o

-1 (Continued) Physical Outcomes mproved No Change Follow-up See MacKeen et al.178 HR Rate-pressure prod eight Lean mass None infolds fat Weight None BP None SBP, RDBP, EDBP EHR None (obese only) None HR Vo2max infolds Skinfolds Program continued for 2max Weight 17 months; tested at ctic acid Blood lactate 2, 5, 11, and 17 WC RHR ax work load EHR 2max %fat Lean mass 2max Total cholesterol R 2max ight (M only) ight MI 2max BP, RDBP (M only) um triglyceride (F only)

Lewis et al.173 Supervised 9% MacKeen et al.178 18-month follow-up of W R Franklin et al.166 E H E 64 Morrison et al.174 Supervised 22 V Netz et al.175 ?high Seals et al.176 Supervised 22 E Home-based then C White et al.177 29 supervised EH W One class/wk supervised V plus home-based W R E B C R W R R M E Endurance = time spent in standard exercise task; EDBP = exercising diastolic b blood pressure; RHR = resting heart rate; Vo2max = maximal oxygen capacity; = low-densitylipoprotein level; RSBP = resting systolic blood pressure; PWC Source: Adapted from Lee,87 pp 136-137, with permission.

%fat Serum triglyceride None Weight Total cholesterol RHR, EHR ESBP Physical activity Yes HDL:LDL ratio None Endurance Vo2max %fat Vo2max Endurance EHR None Cardiac efficiency Cardiac output HR Blood lactate Weight Vo2max Weight RHR ESBP Blood lactate Cardiac efficiency RHR Weight RSBP (down) RDBP (up) Muscle strength Endurance blood pressure; HDL = high-density lipoprotein level; RDBP = resting diastolic ; EHR = exercising heart rate; ESBP = exercising systolic blood pressure; LDL C = physical work capacity.

CHAPTER 3 3 Training for Strength DAVID H. CLARKE, Ph.D. DEFINITION OF STRENGTH ISOKINETIC EXERCISE ISOTONIC TRAINING ISOMETRIC TRAINING HYPERTROPHY OF SKELETAL ISOTONIC VERSUS ISOMETRIC MUSCLE TRAINING AGING AND STRENGTH ECCENTRIC TRAINING DEVELOPMENT with proper training, women can become very strong. However, even with the same strength-training program, their muscles will not enlarge as much as those of men. The data-based studies regarding the adaptations resulting from strength training have come predominantly from research conducted on male subjects, but, aside from questions raised concerning muscle hypertrophy, it seems tenable to conclude that principlesthat apply to men also apply towomen. DEFINITION OF STRENGTH The first concept that needs to be defined is that of strength. A dictionary definition is unacceptable, as the terms \"tough,\" \"powerful,\" and \"muscular\" do very little to describe what is actually a functional concept. Attempts at obtaining a true measure of muscle force show that maximum tension varies from 1.5to 2.5 kg • cm–2 in vertebrate nonhuman muscles and perhaps slightlyhigher in the nor- mal human.1 Thus, if one assumes a value of 3 kg • cm–2 and that large muscles of the thigh may have 100 cm2 of cross section, the resulting internal force that could be developed would be 300 kg. Obviously, the amount of useful torque that can be marshaled during normal activities must be expressed somewhat differ- ently, since it is not feasible to determine true internal tensions. Thus, it is cus- tomary to employ the concept of the maximal voluntary contraction (MVC), which implies that the effort is not submaximalor created by some external stim- ulus, such as a tetanic shock. Yet one does not know whether the contraction resulted in any movement, whether it caused any muscle shortening or length- ening, and, if movement did occur, whether it was at a fixed speed or whether 6O

Training for Strength 61 the tension on the muscle was constant or 10 RM. When an appropriate number of ad- variable. ditional repetitions of the 10 RM could be performed, more weight was added and the Mastering the terminology helps one not process continued at this new 10-RM weight. only to understand the literature on It is generally thought that keeping the total strength training but also to comprehend number of repetitions for the three sets the difficulty faced by investigators in quan- somewhere in the range of 30 to 35 enhances tifying the results of various training regi- the development of muscular strength. mens. There are few absolute standards Using a program with reduced resistance available for the assessment of strength, so and increased repetitions is thought to em- a wide variety of procedures has been em- phasize muscular endurance. Houtz, Par- ployed. Thus, there has been great difficulty rish, and Hellebrandt3 applied the PRE prin- in makingclear comparisons among various ciple to female subjects, exercising the studies. In the present context, isotonic quadriceps and forearm muscles, and found strength (or dynamic strength) of a muscle is that strength more than doubled in 4 weeks. defined as the maximum force that can be Thus, it seems probable that the principles exerted by that muscle during contraction of strength development can be successfully as it moves through its full range of motion. applied to women as well as men. This can be further delineated into concen- tric (i.e., shortening) and eccentric (i.e., Interest in refining the procedures forPRE lengthening) forms. Isometric strength (or for effective strength gains has been the sub- static strength) is a single MVC performed ject of fairly intense investigation in the by a muscle group in a static position, in subsequent years. Berger4 has provided which no shortening or lengthening of the considerable insight into the strength muscle occurs; isokinetic strength resembles development process, using various combi- the isotonic contraction, since the joint nations of repetitions, sets (number of re- moves through a range of motion, but the peated sequences the exercise is performed speed of movement is held constant. This during a given session), and number of latter system requires specialized equip- training sessions per week. The criterion ment to control for a variety of movement measure of muscular strength was the 1 RM, speeds. defined as the maximum amount of weight that could be successfully moved through a ISOTONIC TRAINING complete range of motion for one repetition. In one study,4 Berger trained six groups for The usual method of training has been to 12 weeks employing the bench press exer- follow a routine of isotonic exercises. A sys- cise. The groups used resistances of 2, 4, 6, tem described by DeLorme and Watkins2 8, 10, and 12 RMas their training modalities during the period immediately following and performed only one set of repetitions World War II became known as progressive per training session. At the end of this time resistance exercise (PRE) and was based on it was found that those training at four, six, a set of 10 repetitions maximum (10 RM), and eight repetitions gained significantly which is the heaviest weight that can be greater amounts of strength than any of the lifted and lowered 10 times in succession. other groups, suggesting that an optimum The manner in which these exercises were target for training would be to perform be- to be employed was first to perform a set of tween three and nine repetitions. Using one, 10 repetitions of one half of the weight of the two, and three sets of repetitions and em- 10 RM, then to perform a second set of 10 ploying 2, 6, and 10 RM as the weights and repetitions at three fourths of the weightof numbers of repetitions in each set, he found the 10 RM, and finally to perform as many that no advantage was gained by exercising repetitions as possible at the weight of the with heavier loads for 2 RMthan with lighter loads at 10 RM.5 All combinations resulted in

62 Basic Concepts of Exercise Physiology significant strength increases, but strength each other. Thus, it appears that strength gains were maximal when the number of gains are greatest when resistance is high. repetitions per set was 6 RMfor three sets. Since few repetitions can be done using high To determine whether increasing the num- resistance, a smaller time expenditure is re- ber of sets beyond three would lead to quired for this training. greater gains in strength, Berger6 compared the strength achieved by performing 2 RM The question ofwhether an effective train- for six sets, 6 RM for three sets, and 10RM ing response can be elicited for women may for three sets. He found that all three groups be answered in the affirmative, at least if the gained significantly and similarly in intensity of the training program is high strength. This suggests that there is a point enough, and if the program lasts long beyond which gains in muscular strength enough. Staron et al.9 submitted adult should not be anticipated. women to such a program of high-intensity, heavy-resistance exercises of the lower ex- Berger and Hardage7 studied an alternate, tremity for 20 weeks. A significant increase somewhat unique modification of the 10-RM in the 1 RM was found for each exercise, training technique. One group performed 10 even though the subjects trained only twice repetitions for one set, but each repetition a week. was adjusted so that it required maximum ef- fort, that is, a 1 RM.Subsequent repetitions A consideration for most individuals en- were performed by gradually reducing the gaging in weight training exercise has to do load, so that at the 10th repetition the sub- with how long the results of trainingwill per- jects were still exerting maximum tension. sist if the training frequency is reduced. When compared with the regular 10-RM Graves et al.10 recruited both male and fe- group, it was found that both groups im- male subjects who trained for either 10or 18 proved significantly in the 1-RM bench weeks on knee extension, using a 7- to 10- press after 8 weeks of training. However, the RM regimen. Following this 10-week period, 1-RM group improved significantly more the subjects reduced their trainingfequency than the regular 10-RM group, indicating the from a minimum of three times per week to relative importance of intensity of effort in less. Subjects who stopped training alto- training. It should be noted that almost all gether lost 68% of the previously gained studies have shown the importance of at- strength, but those who reduced to 2 and taining maximal tension of the muscles dur- even 1 day per week did not change signifi- ing the course of the exercise. cantly in strength. Thus, a maintenance rou- tine would seem to be possible when train- To compare the strength achieved by per- ing only once per week. forming many repetitions using light weight with that gained by performing few repeti- It has generally been found that men have tions using heavy weight, Anderson and greater absolute amounts of strength than Kearney8 trained 43 male subjects using women under most conditions.11–14 Even un- three sets of 6 to 8 RM for one group, 30 to trained men who have not been specifically 40 RMfor a second group, and 100to 150 RM weight training15 exhibit greater upper and for a third group, all subjects employing the lower body strength than female athletes bench press three times per week for 9 trained in such sports as basketball and vol- weeks. Strength was assessed with the 1-RM leyball but not weight training. The ratios bench press, administered before and after comparing the strength of women to that of the training. Gains in strength were men are on the order of 0.46 to 0.73 when achieved by all three groups, but only the compared on maximal strength of elbow high-resistance, low-repetition (6- to 8-RM) flexion, shoulder flexion, back extension, group was significantly stronger than the and hand grip.16 Even though this is the case, other two groups, which did not differ from the established principles of strength train- ing are applicable to both men and women.

Training for Strength 63 ISOMETRIC TRAINING These principles were applied to postpu- bescent young men who were trained in The systematic use of isometric training wrist flexion employing the Hettinger and principles can probably be traced to the Muller strategy17 of two-thirds maximum 1953 report of Hettinger and Muller,17 who tension for one 6-second period each day. found an average strength increase of 5% This was compared with a technique in per week when the muscle tension was held which 80% of maximum strength was em- for 6 seconds at two thirds of maximum ployed in five 6-second periods.23 Both strength. Even when the tension was in- groups of subjects improved significantly creased to 100%,or when the length of time after 4 weeks of training, although no signif- was increased, very little additional im- icant difference resulted between the two provement was noted. Isometric exercises groups. This suggests that a single 6-second are normally performed by establishing a bout of isometric exercise on a daily basis is given joint angle and exerting isometric ten- about as effective for developing muscular sion at that point in the range of motion strength as bouts practiced more frequently (e.g., pushing against a stationary wall). As and at higher tensions. Furthermore, high with isotonic exercises, more than one set school boys and girls training for one con- may be performedand the length of time for traction per day at 25%,50%,75%, and 100% which the tension is exerted may vary. How- of maximum isometric elbow flexion ever, the amount of the strength gain sug- strength were compared after training.24 gested by Muller18 has not been confirmed in With the exception of the 25% resistance subsequent experimentation. It seems more group, all groups became stronger. Thus, likely that the amount of strength gainwould the age of subjects seems to be of little con- depend on the relative state of training of a sequence for achieving strength-training re- given muscle group. Thus, the closer one is sults. to a theoretic maximum, the more likely the gains are to be small.19 Increasing the number of isometric con- tractions appears to increase the strength Isometric exercise does increase muscu- gain over a greater range of motion.25 One lar strength. Josenhans20 employed isomet- group of subjects held three maximum iso- ric exercises for the grip and the flexor and metric contractions at an elbow joint angle extensor muscles of the finger, the elbow, of 170 degrees' flexion, each for 6 seconds, and the knee and found a 40% increase in in a program that was of 6 weeks' duration. muscular force at the end of the trainingpe- Another group performed twenty 6-second riod. When 5-second maximal isometric maximum contractions at the same joint contractions of the quadriceps muscles angle. Maximum strength was assessed be- were employed, it was found that strength fore and after the experiment at angles of increases vary between 80% and 400%.21 both 90 and 170 degrees. All tests used iso- Morehouse22 separated some trained sub- metric maximum contractions. The subjects jects into high- and low-strength groups and who performed more contractions gained employed either 1, 3, 5, or 10 maximum iso- strength significantly at both joint angles, metric contractions each session. Subjects while those who performed fewer contrac- increased significantly in strength after 5 tions became stronger only at the angleof weeks, with similar improvements found re- 170 degrees, the training angle. Thus, the gardless of level of initial strength. Appar- longer duration of work seems to be more ently, most individuals can anticipate in- beneficial for strength development, but the creases in strength regardless of how strong difference is small compared with the they are at the outset, unless they are al- amount of effort required. The evidence for ready in an advanced state of muscular joint-angle-specific effects of isometric training. training is fairly strong, especially when the

64 Basic Concepts of Exercise Physiology muscles are placed at a relatively short ing of six maximalvoluntary contractions at length. This can be accomplished by manip- a predetermined \"sticking point\" in the ulating the joint angle. This specificity of bench press. Analysis of the 1-RM bench training response is difficult to justify if the press before and after the training program training adaptation results in changes in revealed significant improvements for both muscle size. An alternate explanation would groups. However, the experimental group involve some sort of neural adaptation. was significantly stronger than the control Thus, Kitai and Sale26trained the ankleplan- group, providing evidence that isometric tar flexor muscles of women at a joint angle training enhances the standard isotonic of 90 degrees employing two sets of five training routine in the achievement of max- maximal voluntary isometric contractions imum strength. each held for 5 seconds. The training pro- gram was 6 weeks in duration and result- ISOTONIC VERSUS ISOMETRIC ed in significant increases in voluntary TRAINING strength at the training angle and the two adjacent angles at 5 and 10degrees in either It has been difficult to compare the im- direction only. Examination of peak provements in strength resulting from iso- strength of maximum twitch of the involved tonic and isometric training methods, be- muscles would point to a neural mechanism cause the intensities of training in the two as being responsible for this joint specificity methods cannot be equated. The ideal in isometric training.This point has been re- method of comparison would employ two inforced by the finding of an increase in exercise regimens, both of equal workloads. maximal integrated electrical activity at the However, this has been difficult to accom- specific training angle.27 plish because isometric exercises involve no movement and, thus, are difficult to quan- Whereas most investigations have em- tify in physical terms. ployed either male subjects or a combina- tion of male and female subjects,Hansen28'29 Despite the problems inherent in compar- used female subjects, employing sustained ing isotonic and isometric training effects, and repeated isometric contractions. The Rasch and Morehouse,31in one of the earlier gains in isometric strength in this study studies, compared these two methods by ranged from approximately 4% to 11% over having one group (isotonic) perform a 5-RM a 5-week training program. procedure involving three sets of arm presses and curls, taking a total of 15 sec- A more recent development has been the onds to perform, and having the other group incorporation of functional isometrics into (isometric) employ a 15-second exercise pe- an isotonic strength training program. In a riod contracting the muscles isometrically given range of motion, it is common to locate at two-thirds maximum. Following 6 weeks a given point at which the muscle is most in- of training,substantial increases were found efficient. Weight lifters refer to this as the for the isotonic exercise group in elbow flex- \"sticking point\" of exercise. It represents ion and arm elevation and for the isometric the point at which the force available is exercise group in arm elevation alone. No equal to the resistance of the weight. To de- significant gain was made in elbow flexion termine whether the incorporation of maxi- for the isometric training group. Thus, sub- mum isometric contractions at this point jects employing isotonic exercise gained a would permit the development of strength greater amount of strength than did those beyond that provided by the isotonic exer- subjects employing isometric exercises. It cise alone, subjects30 in a control group was suggested by the investigators that trained on the bench press exercise usingan some of the strength development may have isotonic training procedure employing6 to 8 come from the acquisition of skill, since sub- RM, while the experimental group added to this routine an isometric program consist-

Training for Strength 65 jects tended to do better when performing ually increased force to maximum over ap- familiar procedures. This may help explain proximately 4 seconds. The isotonic group sudden early increases in strength; they lifted a load equivalent to 75% of maximum may be attributable more to neuromuscular as far as possible, also over a duration of 4 coordination than to true muscle hypertro- seconds. The exercise involved supination phy. of the left hand and included 12 male and 8 female subjects. All training procedures re- Isometric and isotonic training proce- sulted in a significant improvement in dures were applied to subjects engaging in strength. However, no significant differ- exercise over a 12-week training period, ex- ences were found between the different pro- ercising three times per week and employ- cedures. Chui36 noted similar findings. Two ing the larger muscles of the back.32 The iso- groups trained with rapid and slow isotonic metric group trained with a back pull contractions and were compared with a machine, contracting the muscles for 6 sec- group employing isometric contractions. onds maximally, three sets per exercise ses- The slow isotonic contractions required a sion, and the isotonic group employed back cadence of 4 seconds for movement and re- hyperextension exercises based on an 8- to covery, and the isometric contractions were 12-RM regimen. Both groups improved sig- held for 6 seconds. All groups employed a nificantly in muscular strength, but the iso- weight equal to a 10-RM resistance. No ad- metric group gained significantly more vantage was found for either procedure over when an isometric test was employed, and the other, although each group gained sig- the isotonic group performed better when a nificantly in muscular strength. When iso- test of isotonic strength, such as the 1-RM metric contractions were lengthened to 30 procedure, was used. This finding suggests seconds,37 the development of strength was that training is specific, a concept that has found to be less than by isotonic methods by received additional support from some some 14%, even though both isotonic and studies. isometric methods caused increases in mus- cular strength. This is in contrast, however, to the work of many other investigators who have reported Thus, it would seem desirable to employ similar gains in strength from these two dif- isotonic procedures whenever possible. ferent training methods. For example, Gains in strength with isometric exercise Berger33 trained subjects for 12 weeks both tend to be less consistent than those with isometrically and isotonically and used the isotonic exercise, when many training tech- criterion of the 1-RM test. The final strength niques and strength tests are employed. of the isometrically trained group was not significantly different from seven of the nine ECCENTRIC TRAINING groups that trained isotonically. Coleman34 employed the elbow flexor muscle in a pro- As pointed out earlier, isotonic movement gram of 12weeks' duration,using an isomet- can be divided into a concentric (shorten- ric regimen consisting of two 10-second con- ing) and an eccentric (lengthening) phase. tractions and an isotonic training program It is generally concluded that in isotonic consisting of a 5-RM regimen. In this in- training the greatest force is exerted con- stance, there was an attempt to equate the centrically, and this usually means that the load, duration, and range of motion of the muscle is shortening and the load is being exercise. No significant difference was found lifted against gravity. Thus, loads are ad- between the two methods, although both justed so that the greatest tension is pro- produced significant strength gains. vided during this phase. The eccentric phase is ordinarily employed to complete Salter35 investigated the effect on muscu- the movement so that the muscle returns to lar strength of maximum isometric and iso- tonic contractions, performed at different repetition rates. The isometric group grad-

66 Basic Concepts of Exercise Physiology its original length. The weight is simplylow- 31%. This suggests that during maximum ered slowly with gravity assistance. It is gen- contractions in eccentric movement, the an- erally accepted that the amount of weight tagonistic muscles are also contracted. By that can be lowered maximally is about 20% palpation and by examination of the electro- greater than that which can be lifted against myographic activity emanating from the an- gravity. Logically, one would expect the tagonistic muscle, the investigators verified added force that can be resisted with an ec- that this occurs. This finding illustrates the centric contraction to be a greater stimulus fact that it is very difficult to isolate muscle to strength gain. However, scientific studies activity in the human body. have failed to show any advantage of eccen- tric over concentrictraining. More recently, Johnson and co-workers40 trained subjects with eccentric movements Bonde Petersen38 studied isometric, iso- on one arm and leg and concentric move- tonic, and eccentric contractions in female ments on the opposite arm and leg, three and male subjects for a period lasting from times weekly for a period of 6 weeks. The 20 to 36 days. Training for each subject con- specific exercises included the arm curl, arm sisted of one of the following protocols: 1 press, knee flexion, and knee extension. maximum isometric contraction daily, 10 Each exercise lasted for 3 seconds. The con- maximum isometric contractions daily, or centric movement was performed against a 10 eccentric contractions daily. It was found resistance of 80% of the subject's 1-RM that performanceof one maximumisometric strength, and the eccentric movement was contraction daily had no effect on the iso- against 120% of 1 RM. Both exercise pro- metric strength of the subjects; performance grams resulted in significant gains in of 10 isometric contractions daily caused no strength in all subjects, but neither training change in the strength of the female subjects procedure produced gains that were signifi- but led to a significant increase (13%) for the cantly different from the other. Interest- male subjects. Subjects who trained with the ingly, the subjects felt that the eccentric 10 daily eccentric contractions failed to training movements were easier to perform demonstrate any significant increase in than the concentric movements. strength. This lack of significant strength gain may have been due to training every Jones and Rutherford41 included a group day rather than every other day. It is possi- of subjects who trained by eccentric and iso- ble that insufficient time was allowed be- metric procedures as well. In each case sub- tween training sessions to recover com- jects trained knee extensor muscles three pletely from the previous trainingsession. times per week for 12 weeks. The isometric group held a contraction of 80%of maximum Singh and Karpovich39 designed a study to for 4 seconds, the concentric group trained determine the effect of eccentric trainingon at an intensity of 6 RM, and the eccentric a muscle group as well as on its antagonist subjects employed a resistance of 145%of (the opposing muscle complex). In this in- the concentric strength. A large and signifi- stance, the forearm extensors were given 20 cant increase in isometric force occurred, maximum eccentric contractions four times and these gains were significantly greater per week for 8 weeks, and the extensors as than found for both concentric and eccen- well as the forearm flexors were tested for tric training. Even though there was no sig- maximum strength before and after training. nificant difference between concentric and Concentric and isometric strength of the ex- eccentric training regimens, both programs ercised muscles increased approximately resulted in significant increases in strength, 40%, but the eccentric strength increased approximately 15%for the concentric train- only 23%. When the antagonistic muscles ing and 11%for eccentric. were examined, it was found that they also increased in strength, ranging from 17% to The perception that eccentric exercise is easier to perform would seem to lead sub-

Training for Strength 67 jects to greater compliance and acceptabil- studied groups that exercised isometrically, ity of such training. However, present equip- isotonically, and isokinetically for a 4-week ment and common training habits do not period. Significant increases in isometric permit isolation of eccentric contractions. strength occurred for all groups, with one Moreover, since a muscle can resist greater exception: when the isotonic group was force in an eccentric contraction than in a tested at 90 degrees rather than 45 degrees, concentric contraction, considerably no significant improvement was noted. greater tension is required in the eccentric None of the groups improved significantly in movement in order to promote strength the quadriceps muscles when tested for iso- gains. Thus, in a regular isotonic exercise kinetic work,but all were significantly better encompassing both concentric and eccen- when the hamstring muscles were tested. tric contractions, the eccentric phase con- tributes relatively little to strength devel- Lesmes and colleagues44 trained male sub- opment, since the amount of force is jects isokinetically on knee extensors and undoubtedly well below the training stimu- flexors four times per week for 7 weeks, at lus during that phase of the exercise. maximal intensity and at a constant velocity of 180 degrees/sec. One leg was trained at 6- ISOKINETIC EXERCISE second work bouts and the other leg at 30- second work bouts, the ratio of work to rest The newest form of exercise used for providing a method of keeping workloads training is isokinetic exercise. It is often re- equal. Isokinetic testing was accomplished ferred to as \"accommodating resistance ex- at various intervals between 60 and 300 de- ercise,\" because, as explained earlier, it has grees/sec. Increased peak torque occurred the unique feature of adjusting to the ability at both 6 and 30 seconds at all intensitiesex- of the muscles throughout the range of mo- cept those between approximately 180 and tion, so that weak spots are eliminated and 300 degrees/sec. It apparently makes some the muscles remain under constant tension difference to train isokinetically, but it de- throughout the movement. Actually,few ac- pends upon the velocity at which one trains tivities produce and maintainisokinetic ten- and the speed at which testing occurs.45 In sion, the arm strokes in swimmingand oar general, trainingat slow speed (60 degrees/ strokes in rowing being the major excep- sec) does not cause significant peak torque tions. Properly designed equipment offers increases, and training at fast speed (240 de- exercise at any one of a range of fixed grees/sec) does not enhance peak torque at speeds; the subject determines the resist- slow speeds. This is another example of the ance by the applied force. Thus, it is possi- specificity of strengthtraining. ble to exercise maximallythroughout a full range of motion using any one of several Thus, isokinetic exercises are effective in speeds. In isokinetic exercise, increased increasing muscular strength but probably force does not produce increased accelera- not more so than isotonic training. The abil- tion but simply increased resistance. ity of isokinetic movements to create maxi- mum tension throughout the range of mo- One of the earlier studies42 compared iso- tion is clearly desirable, but methods of kinetic training with isotonic and isometric measuring strength may not illustrate this training over an 8-week period. The isoki- advantage. Perhaps future studies using netic group increased in total muscularabil- more refined methods to measure gains in ity by 35%, the isotonic group increased strength may show increased gains in 28%, and the isometric group increased ap- strength with isokinetic training compared proximately 9%. Employing quadriceps and with isotonic and isometric training.How- hamstring muscle exercises on 12 male and ever, the specificity of training and the bias 48 female subjects, Moffroid and associates43 inherent in that situation make it difficult to compare results.

68 Basic Concepts of Exercise Physiology HYPERTROPHY OF SKELETAL ence and muscle cross-sectional area. How- MUSCLE ever, male subjects had higher absolute val- ues in strength and hypertrophy than did Based on the evidence presented so far, females. No significant differences occurred heavy resistance exercise unquestionably in thigh muscle size. Thus, even though men results in increases in muscular strength for have larger muscles than women, and men. While some of the experimentation has women normally have low blood concentra- included women, the extent of strength de- tions of testosterone, which might be ex- velopment and muscle hypertrophy for pected to limit the development of muscle women has not been studied as extensively. size, percentage changes in muscle hyper- One of the most striking occurrences for trophy resulting from heavy-resistance men engaged in weight training over an ex- training are similar in men and women. It is tended period of time is the obvious evi- also true that anabolic steroid administra- dence of hypertrophy, as shown by changes tion during training will promote muscle hy- in muscle size accompanying increases in pertrophy in women. However, the adverse strength. The extent of these changes de- metabolic effects of anabolic steroid use out- pends on a number of factors surrounding weigh their potential desirability for en- the strengthening regimen. However, for hancing muscle size. men, high blood levels of androgens ac- count for the increased muscle size. One of the major issues examined over the years has been to clarify the nature of hy- One of the reasons for the reluctance of pertrophy itself. It is clear that size in- women to engage in serious weighttraining creases with strength development, and ex- in the past has been a fear that they would amining the structural changes that take develop the same hypertrophy that men do place within the muscle has been of interest and would look \"masculine.\" Wilmore12 ex- to exercise physiologists and biologists. The amined the strength and body composition term \"hypertrophy\" denotes an increase in of 47 women and 26 men before and after a the size or bulk of the muscle fibers, rather 10-week intensive weight-training program. than an increase in the number of musclefi- Men were found to be stronger than women bers (called hyperplasia). The question of in most measures of strength, but women whether the latter actually occurs as a result were stronger in leg strength per unit of lean of systematic weight training has been the body weight. Both groups made similar rel- subject of a number of investigations. Early ative gains in strength, but the degree of studies concentrated on laboratory animals muscular hypertrophy for women was con- as subjects. Goldspink47 trained mice by siderably less than that noted for men. means of an exercise requiringthe pullingof a weight to retrieve food. He reported a 30% However, when hypertrophy is assessed increase in cross-sectional area of the aver- in a more direct manner, such as by com- age fiber. He also reported a threefold or puted axial tomography (CAT) scan rather fourfold increase in the number of myofi- than by a more indirect procedure of deter- brils per fiber. In working with guinea pigs, mining lean body mass, sex differences in Helander48 found an increase of some 15%in muscle hypertrophy apparently disappear actomyosin as a result of training.The stud- or become minimal.46 Male and female sub- ies suggest that both hypertrophy and hy- jects participated in a 16-week training pro- perplasia take place. gram in which significant strength increases in elbow flexion, elbow extension, kneeflex- One of the earliest studies to report the ion, and knee extension occurred. Percent- formation of new muscle fibers (hyperpla- age changes in strength were not signifi- sia) was published by van Linge,49 who sur- cantly different between males and females, gically implanted the plantaris muscle of fe- nor was any significant sex difference found male rats into the calcaneus. He cut the in relative increases in upper arm circumfer- nerve of the other plantar flexors so that the

Training for Strength 69 plantaris muscle would provide plantarflex- occur in skeletal muscle. Many of these en- ion. The formation of new muscle fibers was zymatic changes are important for the at- observed at the end of a prolonged heavy tainment of muscle endurance, and many training period. Several studies have per- occur duringweight training.The biochem- formed muscle tenotomy (severing the mus- ical changes that take place for the weight- cle tendon at its insertion) to observe the ef- lifting individualare those that are involved fect of training on the muscle that must take primarily in anaerobic metabolism. over the function of the cut muscle. A very rapid hypertrophy takes place after this pro- AGING AND STRENGTH cedure, and fiber splitting and branching DEVELOPMENT have been reported, as well as increases in strength and fiber diameter. It is agreed that aging results in a decrease in muscular strength. The greatest decline, If a muscle is examined repeatedly for sev- however, usually does not take place until eral months after removal of its synergists, after the age of 50. On the other hand, hyperplasia is noted.50 Gonyea51 subjected strength increases markedly during the ad- 20 cats to a conditioning program involving olescent years and reaches its highest value lifting of weights with the right forelimb in the early 20s.53 Klein and colleagues54 against increasing resistance to receive a compared physically active subjects of ages food reward. The program lasted for 34 25 and 66 and found the maximalvoluntary weeks, and the flexor carpi radialis muscle isometric contraction to be 31% greater in was examined to determine any increase in the young subjects. Similar results are found fiber number as a result of low-resistance with isokinetic torque. A study of young and and high-resistance training. The control old tennis players55 found that at all speeds, group experienced no difference in the num- ranging from 30 to 240 degrees/sec, the ber of fibers in either the left or right limb, young subjects generated significantly more and no difference in the number of fibers torque than the older subjects. When com- was found in those that lifted a \"light-resist- pared with inactive subjects, those who ance\" weight. There was a significant in- were active were significantly stronger, and crease in fiber number (20.5%) for those lift- men were stronger than women at all ing the heavy load. This was attributed to speeds. When the data were presented as a muscle fiber splitting. percentage of maximum rather than as ab- solute values, women exhibited a larger rel- Male albino rats were trained by Ho and ative decline in torque at high speeds than co-workers52 in a progressive training pro- men. It should also be noted that when iso- gram against high resistance for 8 weeks. kinetic torque is adjusted for fat-free muscle The number of fibers per unit of cross-sec- mass or muscle mass itself, age-related dif- tional area increased significantly in the ferences between men and women are no weight-lifting animals. The authors sug- longer significant.56 gested that the fiber splittingappeared to be due to some sort of \"pinching off\" of a small Strength increases for older men as a re- segment from the parent fiber or to an invag- sult of resistance training have been clearly ination of the sarcolemma deep into the identified within 12 weeks.57–59 The same muscle fiber in a plane parallel to the sar- holds true for older women. Charette and comeres. co-workers60 trained women aged 64 to 86 years on lower extremity exercises for 12 Under certain conditions, fiber splitting weeks, exercising three times a week,per- seems to occur, but hypertrophy still re- forming three sets of each exercise at 6-RM mains the major mechanism for the size in- intensity. All seven of the exercises resulted crease that results from intense weight in significantly greater increases in strength training. In addition to the structural changes evident from hypertrophy and hy- perplasia, a number of enzymatic changes

70 Basic Concepts of Exercise Physiology than control subjects who did not train. The timal regimen of exercises seems to be six to average gain was 11.5%. When combined nine repetitions maximum undertaken for aerobic and anaerobic training was exam- three sets at least three times a week. Most ined over 50 weeks, Cress and associates61 individuals will be working with a system found that the exercise subjects, aged 72 that is at the very least an isotonic one.How- years, responded to regular exercise train- ever, because some of the equipment cur- ing of the leg muscles some 12%more than rently available is specifically designed to nontraining control subjects. It is significant maximize the tension throughout the full to note that the control subjects curtailed range of motion, many people now use what their normal independent activities by some are called variable-resistance machines (for 34% over the winter months, ostensibly be- example, Universal, Keiser, Nautilus). It cause of a fear of falling in inclement seems reasonably clear that both isotonic weather. and isokinetic exercises can be used suc- cessfully for developing muscle strength. Further examination of the relative distri- Less effective are isometric exercises and bution and size of fiber types of muscles that eccentric contractions. Gains are greater for have undergone such training reveals im- untrained than for trained individuals. Most portant clues regarding muscle hypertro- athletes, male or female, find increases in phy. If one considers that human muscle is strength to come more slowly near the peak composed of a combination of essentially of training. two types of fibers, it helps to understand the response to a functional overload. One Many of the changes associated withmus- type responds rapidly to stimulation, and cle hypertrophy are cellularand thus are not one responds more slowly. The fast type are associated with noticeable enlargement. called fast-twitch fibers (FT) and fatigue With training, men develop greater muscle fairly quickly. On the other hand, the slow- hypertrophy than women, because they twitch fibers (ST) are better adapted to en- have much higher levels of androgenic hor- durance activities, and thus fatigue less mones, but women can become very strong quickly. Age-related changes in men reveal through weight training and still not de- the atrophy of FT fibers,53 but during velop markedly enlarged muscles. The av- strength training the relative area of the FT erage woman should find a number of ad- fibers has been shown to increase signifi- vantages in being physically strong as she cantly.57 The same phenomenon occurs carries out normal activities and engages in with women. Charette's 12-week training other fitness exercise. This may have special program60 caused a 20.1% increase in FT significance with increasing age. fiber area, and Cress's 50-weekprogram61re- vealed an increase of 46%. No evidence in- The principles outlined, not the type of dicates any change in the percentage of the equipment available, should form the basis fiber types as a result of training, so the con- for exercise selection. Selecting appropriate clusion can be reached that not only can el- exercises and establishing an acceptable derly women safely engage in a resistance routine are more important to strength de- training program, but they can expect velopment than the use of certain commer- changes to occur as a result of muscle hy- cial fitness machines. Training with free pertrophy. weights can accomplish the same gains in strength as training with machines. How- SUMMARY ever, free weights are more likely to cause injury, since the weights are unsupported The unmistakable conclusion to be drawn and require somewhat greater skill to use. is that training for strength is a goal that can The individual should choose the appropri- be pursued by both men and women. An op- ate exercises and engage in a systematic and progressive program. Early gains are due to an increase in motor coordination. Those

Training for Strength 71 parisons in untrained men and women ath- gains that occur after several months of letes, age 10 to 69. Med Sci Sports 13:194, training are due to greater muscle strength. 1981. Expecting great gains in strength after a few 16. Yates JW, et al: Static lifting strength and weeks of training is unrealistic, since the ac- maximal isometric voluntary contractions of quisition of strength is a slow and progres- back, arm and shoulder muscles. Ergonomics sive process. Such unrealistic expectations 23:37, 1980. about improvement are a common cause of 17. Hettinger TL, and Muller EA: Muskelleistung attrition among novices. Qualified instruc- und muskeltrainung. Arbeitsphysiol 15:111, tion may be beneficial to many seeking gains 1953. in muscular strength. 18. Muller EA: Physiology of muscle training. Rev Can Biol 21:303, 1962. REFERENCES 19. Muller EA,and RohmertW: Die geschwindig- 1. Ralston HJ, Pollissar MJ, Inman, VT,et al: Dy- keit der muskelkraft zunahme bei isome- namic features of human isolated voluntary trischen trainung. Int Z Angew Physiol muscle in isometric and free contractions. J 19:403,1963. Appl Physiol 1:526,1949. 20. Josenhans WKT: An evaluation of some meth- 2. DeLorme TL, and Watkins AL: Technics of ods of improving muscle strength. Rev Can progressive resistance exercise. Arch Phys Biol 21:315, 1962. Med 29:263, 1948. 21. Rose DL, Radzyminski SF, and Beatty RR:Ef- 3. Houtz SJ, Parrish AM, and Hellebrandt FA: fect of brief maximalexercise on the strength The influence of heavy resistance exercise on of the quadriceps femoris. Arch Phys Med strength. Physiother Rev 26:299,1946. Rehabil 38:157,1957. 4. Berger RA: Optimum repetitions for the de- 22. Morehouse CA: Development and mainte- velopment of strength. Res Q 33:334, 1962. nance of isometric strength of subjects with 5. Berger RA: Effect of varied weight training diverse initial strengths. Res Q 38:449,1967. programs on strength. Res Q 33:168, 1962. 23. Rarick GL, and Larsen GL: Observations on 6. Berger RA: Comparative effects of three frequency and intensity of isometric muscu- weight training programs. Res Q 34:396,1963. lar effort in developing static muscular 7. Berger RA,and Hardage B: Effect of maximum strength in post-pubescent males. Res Q loads for each of ten repetitions on strength 29:333, 1958. improvement. Res Q 38:715,1967. 24. Cotten D: Relationship of the duration of sus- 8. Anderson T, and Kearney JT: Effects of three tained voluntary isometric contraction to resistance training programs on muscular changes in endurance and strength. Res Q strength and absolute and relative endur- 38:366, 1967. ance.Res Q Exerc Sport 53:1,1982. 25. Meyers CR: Effects of two isometric routines 9. Staron RS,et al: Muscle hypertrophy and fast on strength, size, and endurance in exercised fiber type conversions in heavy resistance- and nonexercised arms. Res Q 38:430,1967. trained women. Eur J Appl Physiol 60:71, 26. Kitai TA, and Sale DG: Specificity of joint 1990. angle in isometric training. Eur J Appl Phys- 10. Graves JE, et al: Effect of reduced training fre- iol 58:744, 1989. quency on muscular strength. Int J Sports 27. Thepaut-MathieuC,Van Hoecke J, and Maton Med 9:316, 1988. B: Myoelectrical and mechanical changes linked to length specificity during isometric 11. Montoye HJ, and Lamphiear DE: Grip and training. J Appl Physiol 64:1500,1988. arm strength in males and females. Res Q 28. Hansen JW: The training effect of repeated 48:109, 1977. isometric muscle contractions. Int Z Angew Physiol 18:474, 1961. 12. Wilmore JH: Alterations in strength, body 29. Hansen JW: The effect of sustained isometric composition and anthropometric measure- muscle contraction on various muscle func- ments consequent to a 10-week weight train- tions. Int Z Angew Physiol 19:430, 1963. ing program. Med Sci Sports 6:133,1974. 30. Jackson A,et al: Strength development: Using functional isometrics in an isotonic strength 13. Heyward V, and McCreary L: Analysis of the training program. Res Q Exerc Sport 56:234, static strength and relative endurance of 1985. women athletes. Res Q 48:703, 1977. 31. Rasch PJ, and Morehouse LE: Effect of static and dynamic exercises on muscular strength 14. ClarkeDH:Sex differences in strength and fa- and hypertrophy. J Appl Physiol 11:29, 1957. tigability. Res Q Exerc Sport 57:144, 1986. 32. Berger RA: Comparison of static and dynamic strength increases. Res Q 33:329,1962. 15. Morrow JR, and Hosier WW: Strength com-

72 Basic Concepts of Exercise Physiology 33. Berger RA: Comparison between static train- 48. Helander EAS: Influence of exercise and re- ing and various dynamic training programs. stricted activity on the protein composition Res Q34:131,1963. of skeletal muscle. Biochem J 78:478,1961. 49. van Linge B:The response of muscle to stren- 34. Coleman AE: Effect of unilateral isometric uous exercise. J Bone Joint Surg 44-B:711, and isotonic contractions on the strength of 1962. the contralateral limb. Res Q 40:490,1969. 50. Reitsma W: Some structural changes in skel- etal muscles of the rat after intensive train- 35. Salter N: The effect on muscle strength of ing. Acta Morphol Neerl Scand 7:229, 1970. maximum isometric and isotonic contrac- 51. Gonyea WJ: Role of exercise in inducing in- tions at different repetition rates. J Physiol creases in skeletal muscle fiber number. J 130:109,1955. Appl Physiol 48:421,1980. 52. Ho KW, et al: Skeletal muscle fiber splitting 36. Chui EF: Effects of isometric and dynamic with weight-lifting exercise in rats. Am J Anat weight-training exercises upon strength and 157:433, 1980. speed of movement. Res Q 35:246,1964. 53. Larsson L, and Karlsson J: Isometric and dy- namic endurance as a function of age and 37. Lawrence MS, Meyer HR, and Matthews NL: skeletal muscle characteristics. Acta Physiol Comparative increase in muscle strength in Scand 104:129, 1978. the quadriceps femoris by isometric and iso- 54. Klein C, et al: Fatigue and recovery contrac- tonic exercise and effects on the contralateral tile properties of young and elderly men. Eur muscle. J Am Phys Ther Assoc 42:15, 1962. J Appl Physiol 57:684,1988. 55. Laforest S, et al: Effects of age and regular ex- 38. Bonde Petersen F: Muscle training by static, ercise on muscle strength and endurance. concentric and eccentric contractions. Acta Eur J Appl Physiol 60:104,1990. Physiol Scand 48:406, 1960. 56. Frontera WR, et al: A cross-sectional study of muscle strength and mass in 45- to 78-year- 39. Singh M, and Karpovich PV: Effect of eccen- old men and women. J Appl Physiol 71:644, tric training of agonists on antagonistic mus- 1991. cles. J Appl Physiol 23:742,1967. 57. Aniansson A, and Gustafsson E: Physical training in elderly men with special reference 40. Johnson BL, et al: A comparison of concen- to quadriceps muscle strength and morphol- tric and eccentric muscle training. Med Sci ogy. Clin Physiol 1:87, 1981. Sports 8:35, 1976. 58. Brown AB, McCartney N, and Sale DG: Posi- tive adaptations to weight-lifting in the el- 41. Jones DA, and Rutherford OM: Human mus- derly. J Appl Physiol 69:1725, 1990. cle strength training: The effects of three dif- 59. Frontera WR, et al: Strength conditioning in ferent regimes and the nature of the resultant older men: Skeletal muscle hypertrophy and changes. J Physiol 391:1, 1987. improved function. J Appl Physiol 64:1038, 1988. 42. Thistle HG, et al: Isokinetic contraction: A 60. Charette SL, et al: Muscle hypertrophy re- new concept of resistive exercise. Arch Phys sponse to resistance training in older Med Rehabil 48:279, 1966. women. J Appl Physiol 70:1912,1991. 61. Cress ME, et al: aEnfdfecmt oufsctrleainminogrpohnolVoOgy2miaxn, 43. Moffroid M, et al: A study of isokinetic exer- thigh strength, cise. Phys Ther 49:735, 1969. septuagenarian women. Med Sci Sports Exerc 23:752,1991. 44. Lesmes GR, et al: Muscle strength and power changes during maximal isokinetic training. Med Sci Sports 10:266, 1978. 45. Ewing JL, et al: Effects of velocity of isokinetic training on strength, power, and quadriceps muscle fibre characteristics. Eur J Appl Phys- iol 61:159, 1990. 46. Cureton KJ,et al: Muscle hypertrophy in men and women. Med Sci Sports Exerc 20:338, 1988. 47. Goldspink G: The combined effects of exer- cise and reduced food intake on skeletal mus- cle fibers. J Cell Comp Physiol 63:209,1964.

CHAPTER 4 Endurance Training THOMAS D. FAHEY, Ed.D. FACTORS THAT DETERMINE SEX DIFFERENCES IN ENDURANCE SUCCESS IN ENDURANCE PERFORMANCE EVENTS TRAINING FOR ENDURANCE Maximal Oxygen Consumption Components of Overload Mitochondrial Density Principles of Training Performance Efficiency Body Composition u ntil recently, systematic studies of female endurance athletes were limited. This is understandable because, before passage of Title IXof the Civil Rights Act in 1972, the number of women competing in endurance sports was small.1 This legislation mandated equal opportunity for sports participation in the schools. The American College of Sports Medicine is perhaps the premier organiza- tion for the study of sports medicine in the world. In 1971 it published the Ency- clopedia of Sport Sciences and Medicine.2 This monumental work consisted of over 1700 pages, but fewer than 10 pages were devoted to women and sports medicine. Until 1958, the longest event in women's track and field in competitions hosted by the Amateur Athletic Union of the United States was 440 yards. In 1965, top female runners were threatened with banishment from international competi- tion if they ran in a race longer than 1.5miles. In 1984, the first Olympic marathon for women was held in Los Angeles. Now, it is common for women to compete in endurance events such as ultramarathons, triathlons, and long-distance swim- ming and cycling. FACTORS THAT DETERMINE SUCCESS IN ENDURANCE EVENTS Important factors in endurance performance include maximal oxygen con- csuommppotisointio(nV.3o2Smeaxxd)i,ffmerietonccheos nedxriisatlindeenndsiutyra,npceerfpoerrmfoarnmcaenecfef.icHieonwcyev, earn, dtheboredly- ative changes that occur with training and the basic underlying mechanisms that determine performance are the same in men and women. 73

74 Basic Concepts of Exercise Physiology Maximal Oxygen Consumption Stroke volume is affected by hemody- namic and myocardial factors. It is closely Maximal oxygen consumption (Vo2max) linked to venous return of blood to the heart. is considered to be the best measure of car- The ability of the heart to contract with in- diovascular capacity. Many sports medicine creased force as its chambers are stretched experts think of it as the single most impor- (a phenomenon known as preload) is de- tant measure of physical fitness. It is defined scribed by the Frank-Starlingprinciple.4 as the point at which O2 consumption fails to Many factors affect preload. These include rise despite an increased exercise intensity total blood volume, body position, intratho- or power output. The greater ability of racic pressure, atrial contribution to ven- trained people to sustain a high exercise in- tricular filling, pumping action of skeletal tensity is largely due to a greater Vo2max. muscle, venous tone, and intrapericardial pressure.4 These hemodynamic factors can Vo2max is equal to the product of maxi- have acute and chronic effects on stroke vol- mum cardiac output and maximum arterio- ume, oxygen transport capacity, and per- venous oxygen difference (Eq. 5-1): ception of fatigue. An example is during en- durance exercise where there is a decrease Vo2max = Qmax (a — v)O2max in blood volume due to dehydration or a de- crease in venous tone. There is a compen- where Vo2max is the maximal rate of O2 con- satory increase in heart rate and an increase sumption (in L. min –1), Qmax is the maxi- in perceived exertion. Increased blood vol- mum cardiac output (L.min–1), and (a — ume resulting from endurance training also v)O2max is the mOa2.x1i0m0ummLa–r1t)e.rTiahl-uvse, nVoou2ms Oax2 causes an increase in stroke volume. difference (mL is a function of the maximum rate of oxygen Stroke volume is also affected by myocar- transport and oxygen utilization. dial contractility. The contractile force of During the transition from rest tomaximal the myocardiumchanges in response to cir- exercise, there is a linear increase in (a — culating catecholamines, the force-fre- v)O2. Arterial oxygen partial pressure (Pao2) quency relationship of the muscle, sympa- is well maintained in most athletes during thetic nerve impulses, intrinsic depression, exercise. The increase is due to the decrease loss of myocardium, pharmacologic depres- in venous oxygen partial pressure (Pvo2). sants, and inotropic agents. Positive inotro- There is only a limited capacity to increase pic agents include digitalis, and negative oxygen extraction through endurance train- inotropic agents include hypoxemia, hyper- ing. The venous blood draining the active capnia, and acidosis.4 Endurance training muscles of both trained and untrained peo- increases myocardial contractility by in- ple during maximal exercise contains rela- creasing Ca++-myosin ATPase activity.5.6 tively littleoxygen. The combination of increased preload and To be successful in competition, athletes contractility is responsible for the increase in sports that require endurance must have in stroke volumethat occurs with endurance a large cardiac output capacity. Maximum training. Both of these factors are limited by cardiac output is the product of maximum ventricular volume, which is affected by ge- heart rate (HR) and maximum stroke vol- netic and environmental factors during ume (SV) (Eq. 5-2): growth and development. It can be changed to some extent through endurance train- Qmax = (HRmax)(SVmax) ing.7,8 Maximum heart rate is largely determined The relative importance of genetics and by heredity and age. It is not appreciably af- environment for success in endurance ex- fected by training.Because HRmax and (a — ercise is not known. Roost9 examined car- v)O2max are stable, changes in Vo2max with diac dimensions in trained and untrained training are mostly due to changes in stroke volume.

Endurance Training 75 school children. All of the trained children ular wall thickness increases, with no in- were classified as talented, with potential for crease in left ventricular volume.24,25 eventual success in endurance events. He Changes in Vo2max and in endurance capac- could find no children with congenitally en- ity are not the same. Endurance perfor- larged hearts. Thus, considering left ventric- mance can be improved by much more than ular diameter and wall size, the importance 20%. This is possible by improving mito- of genetic predisposition for success may chondrial density, speed, running economy, have been overstated. and body composition. The oxygen consumption capacity of a muscle varies according to fiber type.10 The Factors Limiting Vo2max ability of the mitochondria to extract oxygen from blood is approximately three to five The limiting factor of Vo2max has been a times greater in slow-twitch red than in fast- source of debate for many years. Proposed twitch white fibers. Trainingcan double the limiting factors include cardiac output, pul- mitochondrial mass.11 It is possible for elite monary ventilation, lung diffusion, and oxy- endurance athletes to have 10 times the genutilization. muscle oxygen-extracting capacity in their trained muscles as sedentary people. Sev- A basic experimental design for determin- eral studies have demonstrated a high cor- ing if oxygen supply or utilization is the lim- relation m(ritoc0h.8o0n)drbieatlwaecetnivVityo.21m2,1a3x and leg iting factor involves artificially increasing muscle Cardiac the supply of oxygen to the workingmuscle. output and muscle mitochondrial capacities If maximal oxygen consumption does not are important determinants of the upper change, it implies that the ability of the tis- limits ofVo2max. sues to utilize oxygen is the limiting factor. There is a strong genetic component for On the other hand, if Vo2max increases with Vo2max.14–17 The well-knownexercise phys- an artificial increase in O2 to the muscles, iologist Per-Olaf Åstrand has stated that to cardiac output probably is the limiting fac- become an Olympic-level endurance athlete tor. Considerable evidence suggests that requires choosing one's parents carefully! cardiac output is the limiting factor for max- Genetic studies typically show less variance imal aerobic capacity. Vo2max is increased if in Vo2max and muscle fiber type between the rate of oxygen supply to the muscle is in- monozygous twins than between dizygous creased through induced erythrocythemia twins. However, these studies also show (blood doping) or breathing 100% oxygen that training is critical for success, but the during exercise.26–28 ability to improve performance in response to an endurance training program depends Another technique for investigating this on genetic factors. question is to vary the amount of active tis- Intense endurance training results in a sue requiring increased oxygen during ex- mmaaxteilmyu2m0%i.n18c–r2e1 aHseowienveVro, 2gmreaaxteorfinacprperaosxeis- ercise.29–31 Adding active arm work during are possible if the initial physical fitness of maximal treadmill exercise does not in- the subject is low.22,23 Only certain types of crease Vo2max. This type of exercise in- exercise promote the cardiac alterations creases the amount of tissue that requires necessary for increased Vo2max. Maximal oxygen. Several studies have found that stroke volume can be increased in response Vo2peak in isolated quadriceps muscle was to a volume overload induced by participa- much higher than when the muscle was ex- tion in sports such as running, cycling, and ercised as part of a whole body maximum ef- swimming. In pressure-overload sports fort.29–31 such as weight lifting, however, left ventric- Many exercisers use expressions such as \"I was winded\" or \"my wind gave out on me.\" There is little evidence that pulmonary function limits aerobic capacity at sea level

76 Basic Concepts of Exercise Physiology in healthy people. The lungs have a very to Tbhee1cmrimticHalg.m37iItoncdhiroencdt reisatlimPoat2eiss thought large reserve that enables them to meet chondrial Po2 durin of mito- most of the body's requirements for gas ex- gest that it is above g maximal exercise sug- change and acid-base balance during heavy the critical level.33–35 exercise. Considerable direct and indirect evidence exists for this: Vo2max as Predictor of Endurance Performance • The alveolar and capillary surfaceareas of the system are approximately 140and 125 If Vo2max were the only predictor of en- m2, respectively. The alveolar-capillary durance performance, then endurance con- diffusion distance is no more than a few tests could be decided in the laboratory. Re- microns thick. Thus, the lung has an ex- search scientists could administertreadmill tremely large diffusion capacity. tests. The person with the highest Vo2max would be the winner. This might be easier • Low pulmonary resistance to bloodflow and more precise than conducting athletic allows pulmonary blood volume to in- contests on the track, road, or swimming crease during heavy exercise by three pool. However, Vo2max is only one factor times the value at rest. that determines success in endurance events. • During exercise, the ventilation-perfusion In a heterogeneous sample, women with a ratio increases four to five times above hthiognh.3V8 o2Tmhaisx tend to run faster in the mara- rest. relationship does not exist when the sample is homogeneous (i.e., the • The sigmoid shape of the oxyhemoglobin runners are of the same ability level).39 For dissociation curve allows the mainte- example, Grete Waitz and Derek Clayton had nance of resting values of hemoglobin ox- Vo2max values of 73 and 69 mL.kg–1 •min–1, ygen saturation even when Pao2 drops respectively. These values were measured slightly. shortly after they set world records for the women's and men's marathons. Yet, Clay- • Pao2 changes very little during heavy ex- ercise. A constant Pao2 suggests that the alunnigms pdoorntaonttliimnditicVaoto2mr oaxf,lubnegcafuusnectPioano.23,i3s2 Dempsy and Fregosi32 presented evidence ton's time was over 15 minutes faster than that the lungs may be limiting in some elite male endurance athletes. No such evidence Waitz's. Other factors important for success include speed, the ability to continue exer- has been presented for elite female athletes. cising at a high percentage of Vo2max, lactic In their subjects, Pao2 dropped as low as 65 acid clearance capacity, maximal muscle mm Hg. There was a significant widening in the difference between alveolar oxygen par- blood flow, and performanceeconomy. A high Vo2max is a prerequisite to per- tial pressure (PAo2) and Pao2. They hypoth- forming at elite levels in endurance events. esized that there was a diffusion limitation The minimum values for elite female endur- as well as increased airway impedance at high levels of ventilation in these athletes. ance athletes are approximately 65 mL- kg–1 • min–1 for runners and cross-country Others have argued that oxygen supply skiers. Appropriatevalues for swimmers are does not limit either Vo2max or endur- ance.33–36 Rather, the limiting factors are 55 to 60 mL.kg–1. Cyclists require approxi- mately 60 mL.kg–1. The evidence for a min- biochemical. Suggested limiting factors in- imum aerobic capacity requirement is cir- clude decreases in the rate and force ofmyo- fibrillar cross-bridge cycle activity. Contrib- cumstantial: uting factors may be failure of calcium • All elite endurance athletes have high aer- transport mechanisms or decreased myofi- obic capacities. Even though Vo2max is a brillar ATPase activity. poor predictor of performance among ath-