Effects of Human Pregnancy on Responses to Exercise Above and Below theVentilatory Anaerobic Threshold

摘要

The purpose of this contract is to study the effects of healthy human pregnancyon cardiac autonomic function (Study Number 1), oxygen uptake kinetics (Study Number 2), and acid-base regulation (Study Number 3) at rest and during upright cycling at intensities above and below the ventilatory anaerobic threshold (T(vent)). Study Number 1 is currently in progress and results to date support our hypotheses that cardiac parasympathetic nervous system activity is blunted in the resting state and that sympathetic activity is reduced during strenuous exercise above T(vent) in late gestation. Technical aspects of the study and the testing protocol have been finalized for Study Number 2 and data collection will begin in January 1998. Study Number 3 is essentially complete and supports the concept that arterialized plasma H+ is lower in the pregnant vs. nonpregnant state. However, changes in H+ induced by standardized strenuous exercise are comparable in the pregnant vs. nonpregnant state. Nonpregnant subjects may have greater reductions in the strong ion difference (SID) in response to exercise above (T(vent)), but this is compensated by a greater respiratory response and a reduced arterial plasma carbon dioxide tension. Our results to date support the hypothesis that healthy physically active women can safely adapt to short bouts of strenuous exercise in late gestation.