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.