Exercise During the Childbearing Year

Guidelines for Offering Prenatal Aerobic Conditioning, Strength Training, and Flexibility Exercises

Aerobic Conditioning

• Type. Preference should be given to activities that use large muscle groups and develop cardiovascular fitness. Some experts recommend nonweight-bearing activities, such as cycling and swimming, but this may be too restrictive for many women. Weight-bearing exercise such as walking or jogging may be the most convenient mode of exercise for many. Low-impact aerobics classes, fitness machines (such as step and ski simulators), cycling, water activities in cool water, and most recreational activities are fine too (see Table 4 for activities associated with increased risk). The exercise leader should not be too prescriptive. Correct principles should be taught and the woman permitted to choose activities that she enjoys. However, she should not scuba dive past 12–16 feet deep, nor should she participate in high-altitude hiking or ski-touring due to increased hypoxic risk. Depending on her skill level, a pregnant woman should be very careful and, perhaps, avoid sports and activities that could cause falls (e.g., horseback riding, skating, water and downhill skiing, and contact sports) to minimize potential injuries.

• Frequency of Activity. Generally, 3–5 days/week is recommended (ACSM, 1995). A novice should start with 3 days and gradually build up to 5 days per week, if desired. If more intense workouts are performed, they should be alternated with easy days to facilitate recovery.

• Intensity. Age-predicted HR targets are less reliable during pregnancy. However, the fit pregnant woman exercising at a HR of between 135–150 beats/minute is generally regarded as safe. The beginner should start at a HR between 120–135 beats/minute and, if she desires, gradually work up to a higher level. RPE is probably the best method of determining intensity during exercise with a recommended intensity range of between 12–14. The “talk test” is another safe subjective criteria to use. In late pregnancy, as the gravid uterus presses against the diaphragm, shortness of breath can occur making it more difficult to talk and lowering the intensity at which exercise occurs. Competitors can exercise at a level that exceeds this, but they are also in the group for whom closer monitoring is suggested.

• Duration. 15–30 minutes/day is required for basic fitness adaptations to occur. Lower intensity activities may be performed for extended periods for those who desire more exercise. A well-trained woman can exercise continuously up to 60 minutes/day if she experiences no adverse symptoms.

• Progression. This aspect depends on whether or not the woman was previously active or is just beginning a program. It also depends on whether or not she is an athlete who still wants to compete or just to prevent the loss of fitness. For those who have been training prior to pregnancy, the goal should be to maintain health and fitness rather than increase competitive performance. For those beginning an exercise program, intensity and/or duration can be increased by 5% and/or 5 minutes/week respectively. The best time to make progress is during the second trimester when maternal-fetal risks are lowest (Stevenson, 1997b). The interested reader can find more information on aerobic conditioning in Clapp (1998), Noble (1995), and Pirie (1987).

Strength Training

Using light to moderate resistance, machine or even free-weight lifting exercises are effective to pursue during pregnancy if one adheres to safety principles. The use of weight machines rather than free weights alleviates the fear of maternal-fetal injury by dropping a weight. Careful “spotting” is necessary if free weights are used. Strength workouts should include exercises for at least the following muscle groups: abdominals, back extensors, gluteals, rhomboids, trapezius, external hip rotators, quadriceps, and pelvic floor. Strength development of these muscles is especially helpful in performing daily living activities during pregnancy (e.g., lifting, carrying out household chores, and climbing stairs). Strength training also helps prevent disuse atrophy, which can result in spinal and postural problems as the uterus and breasts enlarge (i.e., forward head syndrome with kyphosis, rounded shoulders, and lordosis). Finally, strength training assists with certain active positions taken during labor (i.e., during first and second stages where standing and draping against a partner or table or assuming a modified squat may be more comfortable and advisable than the supine position) (Horsely, 1998).

One or more sets of 8–12 repetitions for 8–10 different major muscle groups are recommended (ACSM, 1995). Performing resistance exercise 2 or 3 times a week is a good goal. The Valsalva maneuver should be avoided by breathing properly—exhaling while lifting and inhaling when returning the weight load to its original position. Benefits include improved posture and less daily fatigue. After the fourth month of pregnancy, strength or stretching exercises in the supine position may need to be avoided since they could reduce blood return through a compressed vena cava and even constrict blood flow through the abdominal aorta. However, conditions vary with the individual since only 5% of pregnant women show a reduced cardiac output even in late pregnancy (Kerr, 1965). Many women can do supine floor exercises through the seventh month of pregnancy without any hypotensive symptoms such as dizziness or abnormal fetal heart rate. A prudent guideline to follow for women who prefer to continue to perform supine exercise after the fourth month (such as abdominal strengthening, certain weight lifting exercise, or stretching) is to limit the time on the back to one minute or less. Additional information on strengthening exercises can be found in Noble (1995) and, particularly for the pregnant athlete, in Pirie (1987).

Pelvic floor exercises, frequently referred to as “Kegel's,” should be included as part of a pregnant woman's daily routine. The pelvic floor performs a vital function in urinary and fecal control, support of the pelvic organs (avoiding prolapse), and sexual satisfaction of both partners. Also, awareness and control of these muscles may be helpful in order for a woman to relax them during the second stage of labor (Horsely, 1997). Usually at around the fifth month, an increase in pressure around the pelvic area is felt as the uterus grows. Urinary incontinence then becomes a common problem during late pregnancy and the postpartum period. Pelvic muscle strength was increased and symptoms of incontinence decreased during these vulnerable times in a group of pregnant women randomly assigned to perform pelvic floor exercise compared with a control group (Sampselle, Miller, Mims, Delancey, Ashton-Miller, & Antonakos, 1998). The muscles that need to be strengthened are those that, when contracted, will interrupt the flow of urine, although the practice of intentionally stopping urine flow is no longer recommended due to possible infection risk and urine retention (Wallace, 1994). Instead, correctly taught pelvic floor exercises should be practiced at other times. A considerable portion of women are unable to do isolated pelvic floor muscle contractions given only verbal instructions, and many may mistakenly substitute a Valsalva maneuver (Bump, Hurt, Fantl, & Wyman, 1991). Proper assistance from the perinatal educator can prove invaluable in this regard. Several variations of this exercise can be done, but 10 repetitions per set repeated several times through the day are recommended. The woman should learn how to relax the pelvic floor, which will enable easier parturition. Specific pelvic floor exercises can be found in Hammer & Hinterman (1998), Noble (1993), Bump et al. (1991), and Cammu and Van Nyler (1995).

Flexibility

Stretching exercises should be performed as part of the warm-up and the cool-down phases. Static stretches and slow dynamic movements should be included. Breath control and emphasizing relaxation are important. Pectorals, hamstrings, and hip adductors and flexors may need special attention since they have the tendency to become tight. Fear exists that pregnancy hormones will predispose a woman to soft tissue tears if maximal end points are reached; however, no evidence supports this concern. Still, to remain prudent, the woman should not stretch to the point of pain or perform fast, ballistic movements, especially late in pregnancy. In partner-assisted stretches (frequently performed in prenatal classes), the partner must be careful not to push joints into extreme ranges of motion. The reader is referred to Noble (1995) and Pirie and Herman (1995) for further details on stretching exercises.

Warm Up and Cool Down

Warm-up and cool-down exercises are even more important during pregnancy than at other times. The body prepares for exercise during the warm-up phase. Low-intensity activities that use large muscle groups will increase circulation and raise body temperature, thus enhancing neural, connective, cardiac, and skeletal muscle tissue function and theoretically decreasing injury probability. A normal warm-up activity is to perform either general calisthenics or simply the planned aerobic activity at a lower intensity. The onset of perspiration is an indicator of being warmed up. Stretching exercises can follow the warm-up phase to further prepare the tissues for more strenuous activity.

The cool-down phase allows the breathing and heart rate to return slowly to pre-exercise levels and prevents the pooling of blood in the lower extremities. The pulse rate should drop below 100–110 beats/minute prior to stretching before terminating the workout (ACSM, 1995).