Effects of Precooling on 30-km Cycling Performance and Pacing in Hot and Temperate Environments.

This study examined the effects of precooling on performance and pacing during 30-km cycling exercise in hot and temperate environments. 8 trained male cyclists performed 4 trials involving either cooling (PRECTEMP and PRECHOT) or no-cooling interventions (TEMP and HOT) prior to a 30-km self-paced cycling exercise in either a hot (35°C, 68% relative humidity) or temperate environment (24°C, 68% relative humidity). Exercise time was longer in HOT (60.62±3.47 min) than in TEMP (58.28±3.30 min; P<0.001), and precooling attenuated this thermal strain performance impairment (PRECHOT 58.28±3.30 min; P=0.048), but it was still impaired compared with TEMP (P=0.02). Exercise performance in PRECTEMP (54.58±4.35 min) was no different from TEMP. Initial power output was sustained until the end of the exercise in both TEMP and PRECTEMP, but was reduced from the 12th km until the end of the trial in HOT (P<0.05). This reduction was delayed by precooling because power output was reduced only after the 20th km during PRECHOT (P<0.05). Heart rate was similar in all conditions throughout almost the entire exercise, suggesting the maintenance of similar relative intensities. In conclusion, precooling was effective in attenuating, but not completely reversing thermal strain performance impairment and offered no ergogenic effect in the temperate environment.

Six weeks of aerobic training improves VO2max and MLSS but does not improve the time to fatigue at the MLSS.

The purpose of this study was to investigate the effects of a 6-week aerobic training period on the time to fatigue (t lim) during exercise performed at the maximal lactate steady state (MLSS). Thirteen untrained male subjects (TG; age 22.5 ± 2.4 years, body mass 72.9 ± 6.7 kg and VO2max 44.9 ± 4.8 mL kg(-1) min(-1)) performed a cycle ergometer test until fatigue at the MLSS power output before and after 6 weeks of aerobic training. A group of eight control subjects (CG; age 25.1 ± 2.4 years, body mass 70.1 ± 9.8 kg and VO2max 45.2 ± 4.1 mL kg(-1) min(-1)) also performed the two tests but did not train during the 6-week period. There were no differences between the groups with respect to the VO2max or MLSS power output (MLSSw) before the treatment period. The VO2max and the MLSSw of the TG increased by 11.2 ± 7.2 % (pre-treatment = 44.9 ± 4.8 vs. post-treatment = 49.8 ± 4.5 mL kg(-1) min(-1)) and 14.7 ± 8.9 % (pre-treatment = 150 ± 27 vs. post-treatment = 171 ± 26 W), respectively, after 6 weeks of training. The results of the CG were unchanged. There were no differences in t lim between the groups or within groups before and after training. Six weeks of aerobic training increases MLSSw and VO2max, but it does not alter the t lim at the MLSS.