Comparing the impact of the moderate and heavy exercise domains on autonomic control, circulating cortisol, and next-day endurance performance in trained runners

Abstract

This thesis examines the impact of exercise in the moderate and heavy domainson aspects of the hypothalamic-pituitary-adrenocortical axis, cardiac autonomic control, and subsequent high-intensity and maximal endurance performance. To better understand post-exercise autonomic control, we measured heart rate and heart rate variability (HRV) during recovery from exercise in the moderate and heavy domains in ten well-trained endurance athletes. Blood was drawn during recovery for measurement of circulating cortisol. The following day, participants completed three high-intensity intervals before running a 3,000m time trial. Exercise in the heavy domain led to a delay in the recovery of HRV after exercise for the first 20 minutes after exercise with no differences at subsequent timepoints. Exercise in the heavy domain did not increase circulating cortisol or alter whole body metabolism during high intensity exercise the following day; similarly, time trial performance was not impaired following exercise in the heavy domain. These findings suggest that exercise in the heavy domain is well-tolerated by endurance athletes. Further research is needed to better understand these findings in the context of chronic training.