Exercise
Exercise
Questions received:
Responses:
What are the pros and cons of exercise during pregnancy?
9th March 1999
There are various reasons for wanting to exercise during pregnancy. If a woman has participated in an exercise programme before becoming pregnant, she may wish to continue training during pregnancy to maintain her level of fitness. She may also believe that exercise will benefit the fetus in some way and result in a smoother delivery. In a more general sense, exercise is an effective antidote for day-to-day stress and encourages social interaction.
On the other hand, mothers-to-be may be concerned about the possible risk of harming their unborn child by exercising inappropriately. Clearly, a balanced judgement about exercise during pregnancy has to made on the basis of known benefits and risks.
At the moment there is relatively little scientific evidence about the effects of exercise during pregnancy. Recommendations have changed during the last 10 years, and will probably continue to do so as more evidence accumulates. In 1985, the American College of Obstetricians and Gynaecologists recommended that exercise during pregnancy should be for no longer than 15 minutes, the maternal heart rate should not exceed 140 beats per minute, and the core body temperature should not exceed 38° C. These guidelines were designed to ensure the safety of the majority of pregnant women, but were later thought to be too restrictive and did not take account of athletic women. In 1994, they published revised guidelines that eliminated figures for heart rate and duration of exercise and suggested that women "can exercise moderately to maintain cardiorespiratory and muscular fitness throughout pregnancy and the postpartum period."
Pregnancy brings many physiological and structural changes in a mother-to-be. Physiological changes occur in many of the body systems such as the cardiovascular, respiratory, musculoskeletal, endocrine, and digestive systems, while the anatomical changes of pregnancy alter posture, balance, flexibility, and co-ordination. The centre of gravity shifts forward and weight gain of 10-16 kg is common. These changes will modify her response to exercise, and she will need to adapt her exercise programme accordingly.
Cardiovascular Changes
Cardiac output increases by 30% to 50% during pregnancy as the heart adapts to the increased demands placed on it by the enlarging uterus and growing fetus. However, when a pregnant woman is supine, cardiac output decreases beyond the non-pregnant baseline, especially after 28 to 32 weeks gestation. Supine exercises such as some aerobic exercises, sit-ups, and weight lifting on a bench press machine should be avoided because in this position the pregnant uterus compresses the inferior vena cava and reduces venous return to the heart. The resting heart rate increases by up to 7 beats per minute in the first trimester and by 15 beats per minute in the second and third trimesters. There is an increase in blood volume of 35% to 45% over the prepregnant state. Performance in endurance athletic activities may actually improve during the first third of pregnancy as a result of these cardiovascular changes. Changes in blood flow probably occur within the placenta during exercise, although this has still to be demonstrated clearly. Studies of pregnant women exercising in controlled settings have shown that the fetal heart rate increases during the mother’s exercise. Whether this should be interpreted as a sign of fetal distress or simply a response to exercise-induced hormones circulating in the maternal blood stream remains to be determined.
Respiratory Changes
As the uterus enlarges, the diaphragm is displaced upwards by as much as 4 cm. This will reduce the respiratory volumes available during exercise. A slight rise in the rate of breathing at rest is caused by increased progesterone levels. Resting oxygen consumption is increased by up to 20% in later pregnancy.
Digestive Changes
The digestive system system is affected by the presence of the enlarging uterus and physiologically by increased plasma progesterone, a smooth muscle relaxant. The combined effects of these changes contribute to constipation and a slowing of gastrointestinal motility. The caloric requirement of mother and baby gradually increases during pregnancy, and becomes an additional 300 kcal per day in the third trimester. Exercise during pregnancy further increases calorie use, and the mother’s nutrition should reflect these increased needs.
Locomotor Changes
Changes in the musculoskeletal system during pregnancy will affect responses to exercise. The enlarging uterus and breasts move the woman's center of gravity forwards and exaggerates the normal forward curvature of her spine in the lumbar region. This increases the likelihood of back pain. The balance skills required for athletic activities such as gymnastics, ice skating, skiing, golf, and tennis are affected by the changes in center of gravity, and these sports may have to be given up during pregnancy and other activities substituted. Hormonal changes ‘loosen’ the ligaments reinforcing pelvic joints and this may predispose her to diminished co-ordination and a greater risk of injury or sprains.
The pros and cons of exercise during pregnancy
With these adaptations in mind, we can look at the advantages and disadvantages of exercise during pregnancy. Exercise generally improves the mother’s feeling of well-being and may decrease the occurrence of depression and anxiety. Exercise may help to reduce unnecessary weight gain, and speeds her return to normal fitness and physique after her baby is delivered.
Counterbalancing these benefits, there are several disadvantages to be aware of. Exercises involving jarring and bouncing of the body may cause distress to the baby, and should be avoided. Exercise during pregnancy may make back and pelvic pain worse. Significant rises in maternal body temperature during pregnancy may be linked with an increased risk of birth defects. Thus, overheating during exercise may be a risk factor. Exercise may trigger uterine contractions. These are not in themselves harmful, but indicate that the exercise is probably too intense. Exercise should be stopped if they occur, and restarted later at a lower intensity. There is some evidence that strenuous exercise is associated with a decrease in the infant’s birth weight.
There are also several medical reasons for not exercising during pregnancy. Exercise should not be attempted during pregnancy if the mother has significant cardiovascular disease, uterine bleeding, premature rupture of the membranes or placental separation, or an incompetent cervix. Exercise must not be undertaken during a fever. Other medical conditions might also preclude the mother from exercising: anemia, thyroid disease, insulin-controlled diabetes, breech presentation in the third trimester, multiple gestation, or excessive weight gain or loss, although the decision in these cases would be made on an individual basis.
Clearly, it is important to check with your doctor before continuing an exercise programme during pregnancy or beginning a new program. Monitor the effects of exercise carefully, particularly if you want to maintain a vigorous exercise program.
Finally, here are some safety tips for women who exercise during pregnancy:
Ensure that you have sufficient fluid intake before, during, and after exercise to prevent dehydration
10-15 minute warming-up and cooling-down periods should be included in each exercise session
Wear suitable clothing to avoid becoming too hot. Hot tubs and saunas should be avoided after exercise
Do not exercise lying down
Avoid exercises that require repetitive bouncing and jarring movements
Focus on low-impact activities such as stationary bicycling, exercising in water, upper-body aerobic workouts, and walking
Avoid activities that may result in low-oxygen states - for example: scuba diving and mountain climbing
Include a larger proportion of complex carbohydrates in your diet to minimise the risk of fetal ketosis when exercising
Avoid competitive sports where there is a risk of trauma
Avoid exercises such as weight-lifting that involve holding the breath and significantly increasing pressure within the abdomen
Reduce the intensity and duration of exercise as pregnancy proceeds
Look out for any warning signs when exercising: vaginal bleeding, frequent or persistent cramping or contractions, leakage of fluid, persistent or severe headache, excessive swelling or decreased fetal movement are signs to terminate exercise
Be careful when restarting exercise after delivery of the baby. The optimal time to resume is unknown, but generally a minimum of two weeks should be allowed before resuming an exercise programme. Weight training should be delayed for six to eight weeks after birth.
References
American College of Obstetricians and Gynaecologists (1985) Home exercise programs: exercise during pregnancy and the postnatal period. Washington, DC: American College of Obstetricians and Gynaecologists.
American College of Obstetricians and Gynecologists (1994) Exercise during pregnancy and the postpartum period. ACOG Technical Bulletin Number 189. International Journal of Gynaecology and Obstetrics, 45(1), 65-70 (February).
Artal, R. (1992) Exercise and pregnancy. Clinical Sports Medicine, 11(2), 363-377.
Artal, R., Drinkwater, B., and Wiswell, R.A. (1992) Exercise in pregnancy (2nd edition). Baltimore: Williams and Wilkins Publishers.
Bell, R, and O'Neill, M. (1994) Exercise and pregnancy: a review. Birth, 21(2), 85-95.
Clapp, J.F. (1994) A clinical approach to exercise during pregnancy. Clinical Sports Medicine, 13(2), 443-458.
Durak, E.P. (1994) Exercise and pregnancy. Santa Barbara: Medical Health and Fitness Publications.
Goodlin, R.C., and Buckley, K.K. (1984) Maternal exercise. Clinical Sports Medicine, 3(4), 881-893.
Jarski, R.W., and Trippett, D.L. (1990) The risks and benefits of exercise during pregnancy. Journal of Family Practice, 30(2), 185-189.
Morrow, R.J., Ritchie, J.W., and Bull, S.B. (1989) Fetal and maternal hemodynamic responses to exercise in pregnancy assessed by Doppler ultrasonography. American Journal of Obstetrics and Gynecology, 160, 138-140.
Olkin, S.K. (1987) Positive pregnancy fitness. New York: Avery Publishing Group.
Schramm, W.F., Stockbauer, J.W., and Hoffman, H.J (1996) Exercise, employment, other daily activities, and adverse pregnancy outcomes. American Journal of Epidemiology, 143(3), 211-218.
Snyder, J.L. (1990) Aerobic exercise during pregnancy. Journal of the American Board of Family Practice, 3(1), 50-53.
Warren, M.P. (1991) Exercise in women: effects on reproductive system and pregnancy. Clinical Sports Medicine, 10(1), 131-139.
What can be caused by a deficiency of exercise?
23rd March 2000
Taking the rather general and simplistic view that the body as a whole is designed to be active rather than inactive, the negative effects of a deficiency of exercise are not too difficult to arrive at. Here are a few examples of the potential disadvantages:
Potential Weight Gain
Unless the amount of carbohydrate and fat in the diet is reduced to a level comparable with the degree of inactivity obesity becomes a possibility. This is particularly likely in a well-developed, affluent, country where access to food and pressure from advertising can also fuel temptation. Obesity places a strain particularly on the cardiovascular and musculoskeletal systems. This can ultimately lead to further inactivity as the effort and energy involved in moving makes inactivity the easier option, and increases the risk of metabolic disorders such as type 2 diabetes mellitus.
Cardiovascular System
Regular exercise tones the cardiovascular system and the heart, which is a muscular pump, becomes more efficient. Blood flow through the blood vessels speeds up as the heart rate increases. The supply of oxygen and nutrients to the tissues, particularly voluntary muscles, is improved and the waste products of metabolism are more rapidly removed. Ultimately a healthy, and therefore fit, person has a greater cardiopulmonary reserve. Lack of exercise has the opposite effects and the reserves of an unfit person are less. Taxing the cardiovascular system of an unfit person quickly leads to breathlessness and fatigue, even more so if such a person is also overweight for their height and age.
Loss of Muscular Strength & Tone
Skeletal (voluntary) muscle cells shrink if they are not used. This can be seen for example when someone breaks a bone in one of their limbs and has to wear a plaster cast for several weeks - the muscles of the affected limb waste. Careful exercise under the guidance of a physiotherapist is then needed to regain muscle strength after the cast is removed. The old adage 'use it or lose it ' is particularly appropriate to voluntary muscles (as well as brain cells!).
Loss of Bone Mass & Strength
Appropriate exercise involving the limbs and trunk helps to ensure that bone strength is maintained. One of the reasons why women are advised to take regular exercise before, during, and after the menopause is to encourage the maintenance of bone strength and reduce the risk of developing osteoporosis. This condition can occur in men too, and one of the risk factors is inactivity.
Elimination
Leaving aside dietary factors, it is generally felt that people who are inclined towards minimal physical activity are more prone to constipation.
Psychological Well-Being
Exercise may well contribute to psychological well-being. Endorphins (endogenous opiates) released during and immediately after exercise are said to produce feelings of euphoria. Exercise promotes health, fitness, and appearance, encourages shared activity with other people, and reduces stress and anxiety (Willis and Campbell, 1992). Thus a lack of exercise can contribute to a reduction in mental health as well as physical health.
Exercise and fitness contribute to longevity and improvements in recovery time from surgical procedures. Within the United Kingdom general practitioners may prescribe a course of physical activity for those it can help. The type, intensity, and amount of exercise required are well within the capabilities of the average adult, and the benefits associated with exercising and fitness far outweigh the disadvantages (Haskell, 1984). As the lifestyle in affluent countries becomes increasingly sedentary, we need to find ways of incorporating appropriate exercise into our daily activities.
References
Haskell, W.L. (1984) Overview: health benefits of exercise. In: Behavioral health: a handbook of health enhancement and disease prevention, edited by J.D. Matarrazzo et al. New York: Wiley (pp 409-423).
Willis, J.D., and Campbell, L.F. (1992) Exercise psychology. Leeds: Human Kinetics Publishers.
Can I have some information on exercise addiction?
26th June 2000
In western societies great emphasis is placed upon appearance and performance, and for some people this can produce a tendency to become self-absorbed and obsessional about exercising. This has the potential to lead to an addiction to exercise - the daily workout becomes obligatory, even if the person is feeling unwell or is injured from a previous exercise session. Improvement, record-keeping, and calorie-counting become part of the obsession. When exercise addicts are prevented from exercising, they suffer withdrawal symptoms such as irritability, sleeplessness and guilt. For someone with exercise dependency, the exercise controls what they do, rather than the other way around. Although in general exercising can have beneficial effects on health, excessive exercise can result in a number of problems such as stress fractures, joint injuries, immune-system weakening, eating disorders, and in women, menstrual irregularity. Other activities at home and at work can be adversely affected. Addiction to exercise can place an undue burden on both body and mind.
The reasons for exercise dependence are presumably a combination of physiological, psychological, and social factors. In addition to the social pressures mentioned above, it has been suggested that some people become addicted to the feeling of elation produced by the release of endorphins after prolonged exercise, the so-called ‘runner’s high’. Another suggestion is that excessive exercise is a form of escape from problems and conflicts in the person’s life. It has been noted that certain types of athletic activity predispose towards exercise dependence, for example, long-distance running (Pierce, McGowan, and Lynn, 1993) and dancing (Pierce, Daleng, and McGowan, 1993).
References
Pierce, E.F., Daleng, M.L., and McGowan, R.W. (1993) Scores on exercise dependence among dancers. Perceptual and Motor Skills, 76(2), 531-535 (Apr).
Pierce, E.F., McGowan, R.W., and Lynn, T.D. (1993) Exercise dependence in relation to competitive orientation of runners. Journal of Sports Medicine and Physical Fitness, 33(2), 189-193(Jun).