Plasma testosterone and cortisol responses to training-intensity exercise in mild and hot environments

Seven endurance-trained and heat-nonacclimated men (Mean +/- SEM: 20 +/- 1 yr; (V) over dot O-2 = 67 +/- 2 ml.kg(-1).min(-1)) ran in two environments (M: 23 degrees C, H: 38 degrees C; 7 days apart) at two absolute training-intensity velocities (S1: 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+/-3nmol.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 degrees C and 38 degrees 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.