Influence of Prolonged Exercise on the 24-Hour Free Testosterone - Cortisol Ratio Hormonal Profile

Abstract

Aim of the study: This study examined the response of the free testosterone and cortisol ratio (fTC) to prolonged endurance exercise. Methods:A trained sportsman performed treadmill exercise at 70% of maximal oxygen uptake to volitional fatigue. Frequent blood samples were collected over 24 hours and analyzed to determine changes in the fTC ratio. Results:Exercise caused an initial increase in the ratio followed by a rapid decline in the immediate recovery from exercise. Approximately 8 hours into recovery from exercise, there was a pronounced and persistent (~6 hours) secondary increase in the ratio. Conclusions:Results suggest that the fTC ratio responds to intensive exercise, but that aspects of the response can be of a delayed nature occurring many hours into recovery. Exercise scientists who wish to monitor this parameter should be aware that the time course by which they choose to conduct their blood sampling could impact upon the interpretation of their data.

Kinetic modelling of testosterone-related differences in the hypothalamic–pituitary–adrenal axis response to stress

“…Finally, the model also replicates complex daily changes in the ratio of TTS over CORT levels (Fig. 2c), in agreement with experimental observations by Duke et al [26].…”