It is not difficult to acquire good information about prenatal exercise that is specific to aerobic and muscular endurance. Almost anytime you pass a magazine stand you’re likely to see a caption referring to what’s new in exercise for this special population. In fact even the non-trade publications seem to go to great lengths to assure that the information they’re printing is current and accurate.
With respect to prenatal resistance training, however, the information is limited. Once a woman becomes pregnant it may be difficult for her to find approval for beginning such a program. Therefore this article offers a different perspective on exercise and pregnancy, a philosophical perspective focusing on when a woman should train for this important time of life. It is not within the scope of this perspective to address specific exercise prescription.
I often discuss exercise programs with women who suddenly become motivated to begin exercising when they first learn they are pregnant. Although they’re somewhat apprehensive, I encourage them to feel at ease with an appropriate prenatal program because research supports this idea. Furthermore, it has been established that exercise during pregnancy can result in benefits1. My position, however, is that women should train for pregnancy before becoming pregnant. Then the prenatal classes could be more appropriately used as part of a maintenance program throughout gestation.
Pregnancy is accompanied by substantial physiological and morphological changes: increased metabolic rate and heat production, as well as decreased cardiac output, A-VO2 difference, and proprioception have been reported 3,4,6,8,9. Because of this, prudent modifications of the guidelines for designing a general fitness program have been suggested for women who have no complications during pregnancy 2. Further modifications should be considered, even to the point of curtailing the program, for women with certain medical or obstetric conditions 1.
In summary, what we’ve learned from the research is that it is all right, even beneficial, to
exercise during pregnancy. The suggested modifications are simply a way to contend with the natural limitations of the body. The key phrase here is natural limitations of the body. Wouldn’t it be more wise to train prior to conception when a woman would be free of any limitations?
At the risk of arguing semantics, I have substituted “exercise” during pregnancy with “training” prior to conception. The concept of training more clearly defines intent. In terms of pursuing an objective, the elite athlete training to overcome the opponent is similar to the average individual training to overcome the effects of a sedentary lifestyle. It is this establishment of the objective that leads to the development of a prescription of exercise specific to the endeavor or event.
Likewise, a pregnant woman faces continual physiological and morphological opposition throughout her pregnancy. Wouldn’t a training program specific to preparing for these changes seem logical? In addition to the philosophical aspect of “training” versus “exercise” is the even more important issue of intensity.
A specific training program infers work at a greater intensity. Granted, the research now suggests there is no indication that pregnant women need to limit their exercise intensity 1. However, intensity usually refers only to the cardiovascular consideration. It seems rather imprudent to ignore the question of intensity for resistance training. I would hope that competitive athletes do not assume they can continue their normal resistance training intensity during pregnancy.
Additional support for training prior to conception comes from concern about the thermoregulatory response. Artal and others 3 have presented information that the effects of exercise on core body temperature during pregnancy are limited. What is more clearly understood is that fit individuals are better able to regulate their core body temperature 1.
Referring once again to the physiological and morphological changes during pregnancy, there are reasons that limit the ability as well as the desire to exercise at an intense level during pregnancy. Non-weight-bearing activities have proven to be successful alternatives for maintaining a high – intensity , moderate – duration regimen of exercise training throughout the third trimester 5,7. However, pregnancy itself is a weight-bearing activity that increases in intensity for 9 months.
Finally, just what level of conditioning is really necessary? Much of that answer depends on your preexisting level of conditioning. Obviously, the worse condition you are in, the less work you have to do to derive a benefit.
Another way to address this question is in terms of specificity. Can the prenatal exercise program effectively prepare the musculature of the legs, back, and pelvic region to support the additional 20 to 35 lbs, indeed often as much as 40 to 50 additional lbs? Can a woman be prepared to generate the maximal effort required during delivery-repeatedly, often for many hours? Does the prenatal regimen offer her body an opportunity to learn to replace glycogen stores and buffer lactic acid production efficiently?
Just because childbirth is nothing new does not mean we should be remiss in seeking a better way for the sake of women’s wellness.
As an exercise physiologist who trains clients within the scheme of periodization, I feel the value of prenatal exercise classes is that of maintenance rather than a building phase. My philosophy is simply to be as physiologically prepared as possible for any endeavor in life. Ideally, an exercise prescription that is tailored to the individual should be designed to account for her exercise history and lifestyle. This preparation specific to the objective is most logically and prudently achieved prior to conception; afterward, a prenatal exercise prescription should focus on maintenance throughout pregnancy.
1. American College of Obstetricians and Gynecologists. Exercise During Pregnancy and the Postpartum Period. ACOG Technical Bulletin #189. Washington, DC: ACOG, 1994.
2. Artal, R. D.I. Masaki, N. Khodiguian, Y. Romem, S.E. Rutherfod, and RA. Wiswell. Exercise prescription in pregnancy: Weightbearing vs. non-weight bearing exercise. Am. J. Obstet. Gynecol 161:1464-1469. 1989.
3. Artal Mittelmark, R. RA. Wiswell, and B.L. Drinkwater, eds. Exercise in Pregnancy (2nd ed.). Baltimore: Williams&Wilkins, 1991.
4. Artal, R. R Wiswell, Y. Romem, and F. Dorey. Pulmonary responses to exercise in pregnancy. Am. J. Obstet. Gynecol 154:378-383. 1986.
5. Clapp, J.F. III, and S. Dickstein. Endurance exercise and pregnancy outcome. Med. Sci. Sports Exerc. 16:556-562. 1984.
6. Clark, S.L, D.B. Cotton, J.M. Pivarnik, W. Lee, G.D.V. Hankins, T.J. Benedetti, et al. Position change and central hemodynamic profile during normal third-trimester pregnancy and post partum. Am. J. Obstet. Gynecol. 164:883-887. 1991.
7. Collings, C.A., L.B. Curet, and J.P. Mullin. Maternal and fetal responses to a maternal aerobic exercise program. Am. J. Obstet. Gynecol 145:702-707. 1983.
8. McMurray, R.G., A. C. Hackney, V.L. Katz, M. Gall, and W.J. Watson. Pregnancy-induced changes in the maximal physiological responses during swimming. J. Appl. Physiol. 71:1454-1459. 1991.
9. Pivarnik, J.M., W. Lee, S.L. Clark, D.B. Cotton, H.T. Spillman, and J.F. Miller. Cardiac output responses of primigravid women during exercise determined by the direct Fick technique. Obstet Gynecol 75:954-959.1990.
Gregory L. Welch is an exercise physiologist and president of SpeciFit, an agency of wellness and competitive performance enhancement in Seal Beach, California.