Investigation of changes in responses to exercise and in mood during pregnancy

Abstract

This study examined the physiological responses to exercise and concomitant changes in mood at different stages of pregnancy. Ten pregnant and six non-pregnant subjects took part. The pregnant subjects performed a graded exercise step-test at first, second and third trimesters. During the incremental step-test, heart rate, [Vdot]O₂, [Vdot]E and perceived exertion were measured at low, moderate and high exercise intensities. Mood was recorded at each trimester with an adjective checklist. The non-pregnant subjects performed the exercise tests at corresponding times for control purposes. During pregnancy subjects were able to exercise at mean heart rates of 150–170 beats min⁻¹ without complications. Increase in the physiological cost of exercise during pregnancy was most apparent in the first trimester; by the third trimester the cost of exercise was not significantly different from that seen in the controls for low and moderate exercise levels: the control subjects were able to perform more work for the same heart rates throughout the study. Ratings of perceived exertion did not vary between trimesters, but were elevated over those of the control group despite the lower work rate of the pregnant subjects. The general trend in mood changes was towards increased Fatigue and Confusion, reduced Vigour and Friendliness as pregnancy progressed. Results suggest that there is no compelling physiological reason for inactivity during pregnancy, and that psychological factors may be more responsible for any decline in habitual activity during pregnancy.

Keywords:

• Heart rate
• Metabolism
• Pregnancy
• Mood
• Work capacity
• Perceived exertion