Plasma Testosterone and Cortisol Responses to Training-Intensity Exercise in Mild and Hot Environments

Seven endurance-trained and heat-nonacclimated men (MeaniSEM: 20 ± 1 yr; VO₂max = 67 ± 2 ml · kg^-1 · min^-1) ran in two environments (M: 23 C, H: 38 C; 7 days apart) at two absolute training-intensity velocities (SI: 240 m · min^-1; followed by S2: 270 m · min^-1; 10 min each) during the winter months. Blood samples were taken via cannula before (pre) S1 and after S1 and S2. Plasma testosterone (TEST) concentrations increased (p < 0.05) above pre levels after S1 in M (19 ± 3 versus 24 ± 3 nmol · L^-1) and H (18 ± 2 versus 23 ± 3 nmol · L-1), and after S2 in H (18 ± 2 versus 24 ± 1 nmol · L^-1). Plasma Cortisol (CORT) and the molar ratio of TEST/CORT were unchanged from pre levels after S1 and S2 during M and H. No differences were found in plasma TEST, CORT, or the molar ratio of TEST/CORT between M and H. These results indicated that circulating levels of TEST and CORT were not changed in endurance-trained, heat-nonacclimated athletes in response to short-duration running performed at the same absolute intensity in the heat, compared to mild environmental conditions. The lack of significant differences in the molar ratio of TEST/CORT, between the 23° C and 38° C trials, suggested that this short-duration exercise challenge performed in the heat was no more of an anabolic or catabolic stimulus for these athletes.

Key words

Collegiate runners - heat-nacclimated