Exercise prescription for pregnancy

Exercise prescription for pregnancy and during postpartum period Sutima Suwankan Department of Sports Science and Sports Development, Faculty of Allied Health Sciences, Thammasat University 1

Can you exercise during pregnancy?  Can pregnant women do cardio or weight training while pregnant?  Is it safe to lift weights during pregnancy?  How much can they exercise when pregnant?  What activities should be avoided during pregnancy?  When should they stop exercising? 2

Objectives After studying in this topic, students will be able to  Understand anatomical and physiological changes during pregnancy.  Explain exercise programs for pregnancy.  Describe contraindications to exercises and warning signs to terminate the exercises during pregnancy.  Understand adverse effects of exercise on the pregnant woman.  Understand fatal responses to maternal exercise. 3

Guidelines for exercise during pregnancy and the postpartum period  Recommended by American College of Obstetricians and Gynecologists (ACOG)  The recommendations promote exercise for …  Sedentary women  Women with medical or obstetric complications, but only after medical evaluation and clearance  For postpartum  rapid continuation has no adverse effects, but gradual return to former activities is advised. 4

Body changes during pregnancy  Major concerns only with exercise performance.  Anatomical changes  Musculoskeletal adaptations  Physiological changes  Cardiovascular adaptations  Respiratory adaptations 5

Any changes on pregnancy’s posture? 6

Musculoskeletal adaptations  Weight gain increase forces across joints during weight bearing  Discomfort to normal joints, increase damage to arthritic or previously unstable joints.  Major affected areas: hip and knee joints  Lumbar lordosis  low back pain  Changes in posture  loss of balance  risk of falling  Increased ligamentous laxity due to increased levels of estrogen and relaxin hormones  risk for strains and sprains 7

Anatomical changes of the heart during pregnancy  With upward displacement of the diaphragm, the apex is moved anterior and to the left  Changes in EKG 8

Cardiovascular changes during pregnancy 9

Cardiovascular adaptations  Increase in blood volume  Increase in heart rate  Increase in stroke volume  Increase in cardiac output  Decrease in systemic vascular resistance due to….  Increase in uterine vasculature and uteroplacental circulation  Decrease in vascular resistance of the skin and kidney  Circulatory reserve is necessary to provide nutrients and oxygen to both mother and fetus at rest and during moderate but not strenuous physical activity 10

Cardiovascular changes during pregnancy 11 Reference: cardiovascres.oxfordjournals.org

Important considerations associated with cardiovascular changes  Body posture during exercise  What postures are at risk of losing consciousness?  Supine position  the enlarging uterus compresses both the inferior vena cava and the lower aorta which reduces venous return to the heart and decrease in cardiac output  Static standing  decrease in cardiac output  Unclear evidence on maternal heart rate response to submaximal exercise during pregnancy  HR monitoring for guiding exercise intensity is difficult during pregnancy 12

Respiratory adaptations  Vital capacity (VC), total lung volume (TLC) and FEV1 remain unchanged  Small decrease in total lung capacity: compensatory increases in diameter of the chest and ribs  During 2nd trimester, expiratory reserve volume (ERV), residual volume (RV) and functional residual volume (FRV) are progressively decreased ~ 20%  Inspiratory reserve volume (IRV) is increased  Increase in minute ventilation: due to increased tidal volume  Decrease in oxygen availability for the performance of aerobic exercise  Enlarged uterus compress to the diaphragm  increase work 13 of breathing

Respiratory changes during pregnancy 14

Respiratory changes during pregnancy  Reduced airway resistance due to the progesterone hormone  Bronchial and tracheal smooth muscle relaxation  Increases respiratory rate ~ 15%  Increase tidal volume ~ 40%: due to hypersensitivity to CO2  Dead space remains unchanged  alveolar ventilation increase ~ 70% 15

Medical screening before exercise  The overall health, obstetric, and medical risks  The nutritional, cardiovascular, musculoskeletal conditions  Fetal well-being  Complications may develop in pregnant women regardless of the previous level of fitness  Absolute contraindications  Relative contraindications 16

Absolute contraindications to aerobic exercise during pregnancy  Heart disease  Restrictive lung disease  Incompetent cervix (ภาวะปากมดลกู หลวม)  Multiple gestation (ครรภแ์ ฝด ) at risk for premature labour  Persistent 2nd and 3rd trimester bleeding  Placenta previa (ภาวะรกเกาะตาํ ) after 26 weeks gestation  Premature labour during the current pregnancy  Ruptured membranes  Pregnancy induced hypertension 17

Relative contraindications to aerobic exercise  Severe anemia  Unevaluated maternal cardiac arrhythmia  Chronic bronchitis  Poorly controlled type I diabetes  Extreme morbid obesity  Extreme underweight (MBI < 12)  History of extremely sedentary lifestyle  Intrauterine growth restriction in current pregnancy  Poorly controlled hypertension/ preeclampsia (ครรภเ์ ป็นพิษ)  Orthopedic limitations  Poorly controlled seizure disorder  Poorly controlled thyroid disease  Heavy smoker 18

Exercise prescription for pregnancy Type of exercise  Aerobic exercise  Swimming: advantage in creating buoyant condition  Resistance training  Flexibility exercises  Avoid activities that ….  increase the risk of falls such as skiing  increase excessive joint stress such as jumping  high-risk sports: horseback riding, racket  risk of falls/trauma to the fetus  contact sports: boxing, soccer  risk of abdominal trauma  exertion in the supine position 19

Intensity of exercise  For health  3 – 4 METS  any activity that is equivalent in difficulty to brisk walking  For maintaining physical fitness: higher intensity  60–90% of HRmax or 50–85% of VO2max  With the variability in maternal HR responses to exercise, target HR cannot be used to monitor exercise intensity in pregnancy.  RPE  alternative method for monitoring of exercise intensity  For moderate exercise, RPE = 12–14 (somewhat hard) 20

Duration of exercise  Aerobic exercise: up to 30 min  Two concerns for prolonged exercise (> 45 min)  Thermoregulation  Exercise should be performed in a thermoneutral environment or in controlled environmental conditions (air conditioning)  Attention to proper hydration and subjective feelings of heat stress are essential  Energy balance  Energy costs of fitness exercise should be estimated and balanced by appropriate energy intakes 21

Thermoregulatory control  The increased basal metabolic rate and heat production  increase in body temperature during exercise  directly related to the intensity of the exercise  In neutral conditions, core temperature increase ~1.5°C during 30 minutes of exercise and then reaches a plateau  Accomplished by increased conductance of heat from the core to the periphery  through the cardiovascular system and evaporative cooling through sweat  Thermal changes to the fetus: ~ 1°C higher than maternal temperature 22

Nutritional requirements during pregnancy  Increase energy needs for fetus  ~ 1.2 extra MJ (300 kcal) per day after 13th week  Increased further during exercise  In weight bearing exercise  energy requirement progressively increases with the increase in weight  Recommendation: carbohydrate intake 23

Frequency of exercise  3-5 days/week or all days of the week  With no medical or obstetric complications, accumulation of 30 minutes a day on most if not all days of the week Progression  Gradual progression of up to 30 min a day  Pregnancy is not a time for greatly improving physical fitness  highly trained women should exercise caution in engaging in higher levels of fitness activities during pregnancy.  The overall activity and fitness levels may decline as pregnancy progresses 24

Warning signs to terminate exercise  Vaginal bleeding  Dyspnea before exertion  Dizziness  Headache  Chest pain  Muscle weakness  Calf pain or swelling  Preterm labour  Decreased fetal movement  Amniotic fluid leakage 25

Adverse effects of exercise on the mother  Hyperthermia: high-intensity exercise could increase body temperature  Avoid exercising in hot conditions for long duration  Wear light-colored, breathable fabrics  Check temperature before and after the longest workout  Hypoglycemia  Monitor blood sugar levels weekly  level > 55 to 60 mg/dl  Oxygen deficit  Avoid performing extreme levels of exercise  affect fetus's HR  Design exercise program with cool-down period of gentle exercise  Dehydration  Drink sufficient water: 6 – 8 oz for every 15 min 26

Fetal responses to maternal exercise  Transient hypoxia  fetal tachycardia, increase in fetal BP  Protective mechanisms allowing the fetus to facilitate transfer of O2 and decrease CO2 tension across the placenta.  Acute effects  fetal HR changes  Chronic effects  intrauterine growth restriction ?? Unclear evidence on fetal heart rate  Increase ~10–30 bpm over baseline during or after maternal exercise  Lowering in fetal HR, bradycardia during maternal exercise  Mechanism causing bradycardia: vagal reflex, cord compression, or fetal head malposition 27

Pregnancy and sports participation  Healthy pregnant women can participate in sports without affecting the outcome of the pregnancy  consider type, intensity, duration and frequency of exercise  Avoid maximal-intensity exercise, have a thorough cool- down period of gentle exercise, avoid excessive stretching and jerky ballistic movements, ensure adequate fluid intake, and pay attention to core body temperature  Physical activity and competition can be engaged in up to the 3rd month unless complications present 28

Exercise for the post partum period  Physiological and morphological changes of pregnancy persist for 4-6 weeks post partum  physical activity can be resumed as soon as physically and medically safe.  Vary from one woman to another, with some being capable of engaging in an exercise within days of delivery.  Moderate weight reduction while nursing is safe and does not compromise neonatal weight gain.  Should feeding infants before exercising in order to avoid the discomfort of engorged breasts.  Avoid problems associated with increased acidity of milk secondary to any build up of lactic acid. 29

References  Artal R., O'Toole M. Guidelines of the American College of Obstetricians and Gynecologists for exercise during pregnancy and the postpartum period. Br J Sports Med 2003;37:6-12  Mittelmark RA, Wiswell RA, Drinkwater BL. Exercise in pregnancy. Williams & Walkins: 2nd edition, 1991. 30