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To determine if the increases in rectal temperature (T(REC)) during exercise in the heat at a given percent of VO2peak depend on a subject's aerobic fitness level. On three occasions, 10 endurance-trained (Tr) and 10 untrained (UTr) subjects (VO2peak: 60 +/- 6 vs. 44 +/- 3 mL kg(-1) min(-1), P < 0.05) cycled in a hot-dry environment (36 +/- 1 degrees C; 25 +/- 2% humidity, airflow 2.5 m s(-1)) at three workloads (40, 60, and 80% VO2peak). At the same percent of VO2peak, on average, Tr had 28 +/- 5% higher heat production but also higher skin blood flow (29 +/- 3%) and sweat rate (20 +/- 7%; P = 0.07) and lower skin temperature (0.5 degrees C; P < 0.05). Pre-exercise T(REC) was lower in the Tr subjects (37.4 +/- 0.2 vs. 37.6 +/- 0.2; P < 0.05) but similar to the UTr at the end of 40 and 60% VO2peak trials. Thus, exercise T(REC) increased more in the Tr group than in the UTr group (0.6 +/- 0.1 vs. 0.3 +/- 0.1 degrees C at 40% VO2peak and 1.0 +/- 0.1 vs. 0.6 +/- 0.3 degrees C at 60% VO2peak; P < 0.05). At 80% VO2peak not only the increase in T(REC) (1.7 +/- 0.1 vs. 1.3 +/- 0.3 degrees C) but also the final T(REC) was larger in Tr than in UTr subjects (39.15 +/- 0.1 vs. 38.85 +/- 0.1 degrees C; P < 0.05). During exercise in the heat at the same relative intensity, aerobically trained individuals have a larger rise in T(REC) than do the untrained ones which renders them more hyperthermic after high-intensity exercise.

To determine which active-recovery protocol would reduce faster the high blood H(+) and lactate concentrations produced by repeated bouts of high-intensity exercise (HIE). On three occasions, 11 moderately trained males performed 4 bouts (1.5 min) at 163% of their respiratory compensation threshold (RCT) interspersed with active-recovery: (1) 4.5 min pedalling at 24% RCT (S(HORT)); (2) 6 min at 18% RCT (M(EDIUM)); (3) 9 min at 12% RCT (L(ONG)). The total work completed during recovery was the same in all three trials. Respiratory gases and arterialized-blood samples were obtained during exercise. At the end of exercise, L(ONG) in comparison to S(HORT) and M(EDIUM) increased plasma pH (7.32 +/- 0.02 vs. approximately 7.22 +/- 0.03; P < 0.05), while reduced lactate concentration (8.5 +/- 0.9 vs. approximately 10.9 +/- 0.8 mM; P < 0.05). Ventilatory equivalent for CO(2) was higher in L(ONG) than S(HORT) and M(EDIUM) (31.4 +/- 0.5 vs. approximately 29.6 +/- 0.5; P < 0.05). Low-intensity prolonged recovery between repeated bouts of HIE maximized H(+) and lactate removal likely by enhancing CO(2) unloading.