The pregnant exerciser: the risks and rewards of a prenatal exercise program.
Physiological changes that occur during pregnancy directly affect exercise. In addition, several anatomical changes may require modification of specific exercises.
During pregnancy, progesterone, estrogen, elastin and relaxin levels increase. Relaxin and elastin soften connective tissue, allowing the pelvis to expand to accommodate the passage of the baby during birth. However, all joints appear to be affected. The weight-bearing joints are particularly at risk for orthopedic injury. Activities that involve jumping, jarring and rapid directional changes should be avoided. Due to the constantly changing center of gravity, activities that involve balance should also be avoided.
Pregnant women may notice an increase in their flexibility. However, stretching to a point of maximum resistance should be avoided so damage to the joint connective tissue will not occur. This is particularly important to remember when stretching the adductor muscles. Some of the adductors insert into the symphysis pubis (the joint of the pubic bone), and forcefully stretching them could cause separation of this joint. This could result in significant pain and difficulty walking. Other exercises which could result in injury if done improperly include squats and lunges. The hips should not drop below the knees during these exercises to avoid undue stress on the knee ligaments.
Cardiorespiratory and Circulatory Concerns
During pregnancy, blood volume increases 30-50%. The resting heart rate can increase as much as 10-15 beats per minute. Resting [VO.sub.2] levels increase as much as 15-32% due to additional oxygen needs for the fetus. This reduces physical working capacity, especially with weight-bearing exercise. In some women, the energy cost of weight-bearing exercise causes a greater increase in oxygen consumption than non-weightbearing exercise. This should be considered when selecting an aerobic exercise.
During exercise, blood is redistributed from the viscera (a group of organs including the uterus) to the working muscles. The question remains as to how much blood can be diverted away from the uterus before the fetus is affected. Human research is scant, but a meta-analysis of all human research on exercise during pregnancy shows pregnant women have exercised for as long as 43 minutes at heart rates of 144 BPM three times a week with no ill effects on the mother or fetus.
The American College of Obstetricians and Gynecologists guidelines suggest pregnant women use perceived exertion as the best indicator of intensity, and stop exercising when they feel tired. However, many women beginning an exercise program during pregnancy have had little to no prior exercise, and lack the body awareness needed to use perceived exertion as the only indicator for judging appropriate intensity. Setting a conservative target heart range of 6075% of MHR and taking pulse checks every five to 10 minutes during an aerobic workout may be more appropriate for these women.
After the first trimester, the enlarging uterus may compress the vena cave (large blood vessel that returns blood from the lower body to the heart) when lying in a supine position. This compression may decrease cardiac output and cause supine hypotensive syndrome. Symptoms include dizziness, nausea, paleness or flushing, and a sense of claustrophobia when lying on the back. If a mother experiences these symptoms, she should not exercise in a supine position.
There is no research relating exercise in the supine position after the first trimester to fetal defects or deaths. This position is the most effective way to strengthen the abdominal muscles critical for effective pushing during birth. In addition, it may be the most comfortable position to stretch the hamstrings, which can reduce lower back discomfort. If a woman has no symptoms of supine hypotensive syndrome, AFAA recommends women exercise or stretch conservatively in the supine position for no more than three to four minutes, then roll to their sides. Alternative exercises in upright or side-lying positions should be given to women who are symptomatic. Placing two pillows under the shoulders and head to achieve a semi-reclining position is another alternative. Prolonged, motionless standing should also be avoided, as this has been associated with a significant decrease in cardiac output.
Pregnant women should avoid the valsalva maneuver (holding one's breath during strenuous exercise). Make sure women exhale on all effort phases of movement. The valsalva maneuver not only increases blood pressure, but intra-abdominal pressure as well.
Metabolic and Thermoregulatory Concerns
In nonpregnant individuals, moderate aerobic exercise is associated with significant increases in core body temperature. Fit women can thermoregulate body temperature more efficiently, but during pregnancy, basal metabolic rate increases. Although animal studies have associated neural tube defects with high maternal core body temperatures during pregnancy, no research thus far has demonstrated an increase in neural tube or other birth defects among women who exercised during their pregnancies.
The neural tube forms at approximately the 23rd to 28th day of gestation. Women who are considering pregnancy or are early in their first trimester should aid heat dissipation by wearing appropriate clothing, keeping themselves adequately hydrated and exercising in an appropriate climate. Drinking plenty of water is important (especially during the third trimester), as dehydration can precipitate premature labor. Pregnant women should be encouraged to drink before, during and after exercise, and monitor their urine to make sure they're maintaining adequate fluid intake.
Pregnant women also utilize carbohydrates at a greater rate during exercise than nonpregnant women, and fasting glucose levels tend to have greater fluctuations. Therefore, pregnant women are more prone to hypoglycemia while exercising. It is strongly advised they consume complex carbohydrates and protein within two hours before exercise to avoid the risk of hypoglycemia.
Weight gain, fetal growth and changes in the center of gravity can have dramatic effects on posture and certain muscle groups. If efforts are not made to counteract these changes, permanent muscle weakness and postural damage can occur. A good rule of thumb is to strengthen the muscles being stretched and weakened, and stretch the muscles being shortened.
Lordosis (swayback) occurs when the lower back muscles shorten and tighten, while the abdominal muscles are weakened and stretched. Reducing lordosis and maintaining neutral pelvic alignment helps reduce low back pain. The focus should be on stretching the lower back muscles with exercises such as the "cat back" stretch, and strengthening the abdominal muscles. Slow, controlled abdominal curls should be done to prevent undue stress on the linea alba (the seam of fibrous tissue which holds the two sheaths of the rectus abdominus together). In the last trimester, it may be difficult to accomplish effective abdominal curls due to the size of the uterus. Pelvic tilts or abdominal breathing with contraction inward may be more appropriate. Limit the time lying in the supine position to no more than three to four minutes and offer alternative positions for women who are symptomatic of supine hypotensive syndrome.
Kyphosis (rounded upper back) may occur when the weight of the enlarging breasts pulls the shoulders forward. The chin also tends to jut forward. This postural condition results in shortened pectoralis and neck extensor muscles and weakened upper back (rhomboid and trapezius) and neck flexor muscles. Chest stretches such as placing the hands behind the head and pressing the elbows back, and neck extensor stretches such as dropping the chin toward the chest are recommended. Upright and one-arm rows strengthen the upper back muscles. Neck flexor exercises include dropping the chin toward the chest while gently applying resistance upward with the hand against the chin.
Round ligament syndrome affects some pregnant women to varied degrees. The uterus is suspended in the pelvis by six ligaments. The round ligaments run diagonally on either side of the pelvis. These ligaments stretch as the weight of the uterus and baby increase. It usually takes two to three days for the ligaments to adjust to this stretching, which may cause a dull, pulling sensation on either side of the pelvis intermittently during pregnancy. Twisting or changing direction too rapidly can cause spasm of the round ligaments. Therefore, choreograph movements which keep the hips facing front, especially during lateral motion. Also, provide adequate advance cueing for any directional changes.
Diastasis recti (separation of the abdominal muscles) is a painless condition which affects about 38% of pregnant women. The hormonal influences of relaxin and elastin can soften the linea alba. As the uterus increases in size, the linea alba may separate like a zipper opening under too much pressure. Diastasis recti does not appear to be related to how much abdominal strengthening is done prior to or during pregnancy. If this condition occurs, however, abdominal strengthening exercises should be modified according to the degree of separation.
A women should be checked for diastasis at about her 20th week and weekly thereafter, as well as when returning to a postnatal exercise program. Strenuous pushing can cause separation during delivery. A strengthening program after delivery should progress backward from where she left off before delivery, until the diastasis has healed to at least a one-finger width separation. Please refer to "Diastasis Recti Check" on page 26.
Carpal tunnel syndrome occurs from accumulation of fluid in tissues compressing the median nerve. Symptoms include numbness and tingling in the thumb, index and middle fingers when the wrists are flexed or extended. Sleeping with the wrists in a flexed position, exercising in the all fours position or doing wall push-ups can initiate symptoms. A woman who is symptomatic may stretch or exercise in the all fours position for brief periods if she places her knuckles on the floor and shifts her weight slightly more to her knees to keep the wrists in a straight line with the forearms.
Pelvic floor muscle conditioning is critical for all pregnant women. These muscles must support all the pelvic organs, and undergo tremendous pressure from the increasing weight of the uterus and baby. Strengthening exercises like Kegels should be started as early as possible to maintain good support of this region. Women who carry their babies very low may experience uncomfortable pressure in the pelvic floor, especially when doing plies or modified squats. They should be encouraged to pull their pelvic floor muscles inward when they perform these exercises.
Pregnant women should learn how to relax this muscle group to allow smoother passage of the baby through the birth canal. Due to the extreme pelvic floor muscle stretching during delivery, they should also be rehabilitated after birth. Sexual dysfunction and stress urinary incontinence can occur from a weakened pelvic floor. Kegel exercises should become a lifelong habit to avoid such problems.
A good understanding of what happens to a woman's body as a result of pregnancy and birth enables instructors and students to safely modify prenatal exercise programs. It is important to remember that despite the benefits of exercise during pregnancy, it is a time to maintain fitness--not make dramatic improvements. Pregnant women should also maintain a realistic perspective. Exercise can improve many aspects of pregnancy, but does not guarantee a short painless labor, non-Cesarean delivery or healthy baby.
RELATED ARTICLE: Diastasis Recti Check
1. Have the student lie on her back with her knees bent.
2. Gently but firmly place one to two fingers perpendicular to the linea alba at a 90-degree angle to the abdomen, approximately one to two inches below the navel.
3. As the student slowly raises her head and shoulders, check how many fingers you can insert into the map. You may observe a bulge in the central abdominal area as the head and shoulders are raised.
* A separation of one half to one finger is considered normal.
* If there is a separation of two fingers, eliminate oblique work involving trunk rotation. Have her splint the muscle by crossing the hands over the abdominal area as if to hold the seam together, slowly raise the head and exhale. Do not allow the student to elevate the shoulders or raise the head to the point where the bulge appears.
* If there is separation of three fingers, eliminate head raises and leg lowering type exercises. Do abdominal contractions inward with outward breaths and pelvic tilts using the abdominal muscles to tilt the pelvis in various positions (supine, standing, side lying, all fours).
Bonnie Rote, R.N., B.S.N., NACES, AFAA lead consultant, clinical maternal/ infant health specialist and certified Lamaze childbirth instructor, is director of AFAA's prenatal exercise educational programs.
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|Title Annotation:||includes continuing education exam|
|Date:||Jan 1, 1995|
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