Pregnancy causes significant changes within a woman's body. Low back pain has long been acknowledged as a common ailment during pregnancy, but only sparse and remedial exercise recommendations have been offered to sufferers. Stretching, relaxation, and pelvic floor strengthening have been indicated for treatment of pregnancy-related low back pain. Additional concerns of modern day mothers-to-be are related to maintaining their abdominal musculature and physique during and after childbirth. All these issues revolve around the training of the core musculature. Currently, little information is available to personal trainers or pregnant mothers regarding appropriate and safe core training exercises. Program design for pregnant women should be carefully constructed with the cooperation of the individual and their physician. This article offers a review of the literature related to core exercise training and recommendations for specific core exercises that meet the American College of Obstetricians and Gynecologists (ACOG) guidelines but have been previously overlooked or unmentioned in the literature.
PHYSIOLOGICAL CHANGES RELATED TO PREGNANCY
The 2002 ACOG guidelines support regular exercise during and after pregnancy for both healthy and sedentary women. The changes that occur to the body during pregnancy are no longer seen as a limitation; rather, women are encouraged to practice healthy habits during this period. Numerous authors concur that there are few, if any, adverse affects related to exercise during pregnancy for those not determined by their physicians to be at risk of complications (8-10,14,26,27). According to the ACOG, pregnancy is a prime time to make behavioral health changes in a woman's life to better the health of herself and her baby. Pregnancy should not be considered a “state of confinement” (2). By implementing positive and healthy changes, these habits can influence and shape the future of both the mother's and the child's health.
There are many physical changes that take place in a woman's body during pregnancy, both anatomically and physiologically. During pregnancy, one of the most obvious transformations is weight gain. This may cause many changes to a woman both at rest and during exercise. Weight gain may take a toll on the woman's joints resulting in discomfort. Pregnant women typically become lordodic in the lumbar spine, creating a shift in their center of gravity. This shift in low back pain can directly affect posture and balance. Posture should be acknowledged both during exercise and at rest, and quick directional changes should be avoided to decrease the risk of injury (2,15).
Throughout pregnancy, a woman's blood volume increases by approximately 40–50%, stroke volume by 10%, and heart rate by 20%. With these increases, cardiac output may rise almost 50% (15). Not only does this increase cardiac output and blood flow in the mother but it also enhances blood flow and output to the fetus through the placenta (15). As a result of these increases, the woman's mean arterial pressure decreases by 5–10 mm Hg at the second trimester and moderately increases to normal prepregnancy blood pressure levels during the rest of the pregnancy.
RISKS, PRECAUTIONS, AND GUIDELINES
Exercise during pregnancy has been a concern due to its effects on the developing fetus, and it is recommended that pregnant women should consult with their physician before undertaking any exercise program (11). Recent research shows that if the mother is healthy and experiences no complications, fetal injuries during exercise are not likely. However, exercising during high-risk pregnancies may cause complications, such as increased fetal heart rate, intrauterine growth restriction, or fetal bradycardia, which can be caused by vagal reflex, cord compression, or fetal head malposition (2).
According to the American College of Sports Medicine (ACSM), both reproduction and physical activity are a healthy part of life and combining the 2 make for a positive pregnancy (1). These recommendations are intended for women who have been fully evaluated and cleared for exercise by their physician. However, these recommendations come with some restrictions. A commonly mentioned restriction involves supine exercise concerns. Lying supine should be avoided after the first trimester of pregnancy due to cardiovascular changes in the body (2,11,21,23). With the redistribution of blood during exercise, the transportation of oxygen, carbon dioxide, and nutrients are a concern for the developing fetus. During exercise, the mother's body may experience a lack of oxygen while the body tries to keep up with oxygen demands. This could potentially cause fetal tachycardia and increased fetal blood pressure as the baby protects itself. Lying supine and motionless standing can create a decrease in cardiac output because of the blockage of venous return.
It is recommended to avoid any exercise or activity that may place the mother at risk of abdominal trauma (15,21,23). To reduce the risk of balance issues that could lead to falls and subsequent fetal injury, activities that involve abrupt or jarring movements should be avoided (22). Other cited exercises that may increase risks of falls include lunges, squats, and stiff-legged deadlifts (17). Also, graded exercise testing should be avoided if it requires a maximal effort unless under the direction of a physician. It is also recommended that submaximal testing should be stopped at 75% heart rate reserve rather than 85% heart rate reserve (24).
BENEFITS OF EXERCISE DURING PREGNANCY
Much of the research to date regarding exercise during pregnancy is related to direct risk to the fetus, such as abdominal trauma, or alterations in blood supply. Although these concerns must be taken into account, cardiovascular fitness should be encouraged within the ACOG guidelines. Contrary to concerns related to high-risk pregnancies, reports of small fetal heart rate changes are not associated with fetal risk but rather heightened fetal wakefulness during exercise (3). Babies born to mothers who maintained physical activity during pregnancy are shown to be less agitated and more alert (9), are self-quieting, and are better able to handle the stress of labor (15).
Besides the cardiovascular adaptations and benefits previously mentioned, muscular strengthening exercises have long been recommended for the improvement of pregnancy and labor. Before the 19th century, it was believed that enhanced muscular work would benefit the mother in various ways (5). In 1967, Blankfield (5) reported that the primary exercise recommendations of the early 19th century encouraged only light activity during pregnancy, such as croquet. Most authors now agree that unless the mother and fetus are at risk of complications, exercise should be considered an acceptable and regular part of pregnancy (3,5,19). The most commonly reported benefits include easier labor, shorter labor times, and enhanced recovery after birth (5,7,8,11). Brown (7) also cited bone mineral density benefits that may offset lactation-induced bone mineral loss for nursing mothers.
Although early recommendations for more efficient labor and birth included exercises, such as lunges and squats (5), which are now considered contraindications due to risks of falls (17), little beyond pelvic titling exercise were indicated for low back pain sufferers (5). Low back pain relief often involves posture correction training by means of pelvic tilt training, muscular endurance training, and postural stabilization training (5,11-13,18,20).
Other literature encourages abdominal strengthening exercise for the prevention of low back pain but still fails to offer specific exercise choices for the reader (19). Although this recommendation may be correct, the ambiguity of this advice leaves the reader with little useful information. Some authors who have consistently recommended abdominal training limit the choice of exercises to pelvic tilts, Kegel exercises, and various forms of isometrics for the core musculature (5,6,11,12,13,18,20). Talmadge et al. (23) further recommend transverse abdominus (TVA) exercises in the form of an abdominal squeezing action. Performing these TVA exercises may also combine with concomitant pelvic floor muscle contractions similar to Kegel exercises.
For women who have trained hard to develop aesthetically pleasing abdominals, the changes that naturally occur as their child develops in the womb can lead to frustration. As the fetus grows, it causes a natural expansion of the abdominal wall and subsequent abdominal musculature separation via expansion of the linea alba. Depken and Zelasko (11) have found that the degree of separation of the abdominal musculature is decreased if muscular strength training is maintained, without any stress or concerns to the mother or fetus. It is inevitable that the abdominal and core musculature may weaken during pregnancy, (18) especially during the third trimester (13).
GENERAL EXERCISE RECOMMENDATIONS
When assisting any pregnant woman with exercise selection, a complete health history and exercise history should be performed and any possible complications should be taken into consideration. Only a physician may determine the presence or absence of any potential complicating factors. Personal trainers should ensure that all pregnant clients have physician clearance for exercise before recommending exercises.
Just as an exercise program would be designed for a nonpregnant individual, the frequency, intensity, time, and type of exercise should be considered. Both aerobic and strength training exercises can be performed during pregnancy. The aerobic exercises can include any aerobic activity that uses large muscle groups in a continuous motion, such as jogging, swimming, and cycling. Both strength training and flexibility exercises should be individualized for the pregnant woman based on exercise history and safety (1,2). Both weight-bearing and non–weight-bearing exercises are recommended, as long as they are safely modified to meet the mother's individual needs.
ACSM (24) recommends that pregnant women can workout between 50 and 80% of their maximum heart rate range, depending on prepregnancy exercise status. In place of heart rate monitoring, the rate of perceived exertion is a useful tool when monitoring how a woman feels. On a scale of 6–20, a pregnant woman can exert up to 12–14 (somewhat hard) during moderate exercise. Women who are experiencing a healthy pregnancy can follow the same recommendations of approximately 30 minutes of exercise most days of the week (2). Although the ACSM recommends that pregnant women can follow the same general guidelines to exercise as non-pregnant women, all exercises should be modified for the safety of the fetus and mother. The goals of the exercise program may differ from the goals for a pregnant woman. For example, weight loss is usually a main goal for an exercise program but would not be a main goal during pregnancy. The goals of the exercise program should reflect the highest level of physical fitness possible while still maximizing safety for both the mother and the fetus.
Also, a pregnant woman should be encouraged to drink enough fluids before, during, and after a workout and to avoid working out in hot humid conditions. Temperature regulation during pregnancy is important because the mother's core temperature rises 1.5°C during the first 30 minutes of exercise (2). The baby's core temperature is 1°C higher than the mother's core temperature. An increase of any more than 1.5°C in the mother's temperature could potentially cause congenital malformations. Avoiding high heat environments and avoiding elevation of core temperature during exercise will allow the body to dissipate heat by sweating, and when working out in cool environments, the heat production will not exceed heat dissipation, which makes for a safer work environment.
Women with uncomplicated pregnancies are encouraged to exercise during pregnancy. Women who do not follow a regular exercise program before pregnancy should ease into an exercise regime building up to 30 min/d. Regardless of whether the pregnancy is termed uncomplicated, the ACOG guidelines presented in Table 1 should be considered before and during the creation of a workout program during pregnancy (2).
Muscle function is similar between pregnant and nonpregnant exercisers (13). Safe repetitions for muscular work of 12 or more reps while avoiding the Valsalva maneuver have been recommended by numerous authors (4,15,17,24). One special concern that may impact training is change in the mother's center of gravity as the fetus grows. Modifications in exercises should be focused on balance and coordination. To maintain balance during training, core strength and stability are crucial.
Two recent articles that offer specific exercise recommendations indicate the importance of emphasizing strengthening for the adductors, hamstrings, gluteals, upper back, posterior deltoid, and TVA and Kegels (7,15). Exercise recommendations from Pujol et al. (17) further recommend specific core muscular training to indicate the efficacy of the standing leg lifts, quadruplex, abdominal isometrics, abdominal curl ups until the 2nd trimester, seated abdominal machine, side bridge, pelvic tilts, and upper and lower back exercises. A list of exercises that meet all ACOG and ACSM guidelines for training during pregnancy is provided in Table 2. This article is one of the few that offers specific core exercise choices to women and personal trainers. Although these exercise recommendations are helpful, other exercises could be included in an asymptomatic and risk-free women's program.
Fitness does decrease postpartum because demands are placed on the mother that may interfere with her normal exercise routine and also with recovery due to lack of adequate rest and recovery with improvements in fitness postpartum being realized 2 weeks postpartum (25). When dealing with new mothers, individualization of training programs must consider the particular factors that may influence fitness levels. The same exercise list can be used for new mothers once they have been cleared for exercise by their physician for exercises involving abdominal exercise.
Pregnant women meeting the recommended exercise guidelines are typically younger, white, non-Hispanic, more educated, not married, nonsmokers, and have higher incomes than their counterparts who do not meet the recommendations (16). As personal trainers, physical therapists, and athletic trainers work with pregnant populations, extra encouragement may be needed to ensure that all women exercise the proper amount of time, thus gaining the benefits of fitness for both themselves and their child.
Those who have experience working with pregnant populations can attest to words of Pujol et al. (17), who state “the exercise professional will need to be creative in altering exercises to meet the woman's needs and the safety requirements of the fetus.” If this simple yet critical concept is at the forefront of all training, women with uncomplicated pregnancies should be encouraged to take part in fitness programs, which include the core musculature exercises depicted in this article.
The authors would like to thank Nicole Jackson and Alison Haiduke for their assistance with exercise selection and feedback regarding their efficacy and usefulness.
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