Ball D, Burrows C, Sargeant A J
Department of Exercise and Sport Science, Manchester Metropolitan University, Alsager, UK.
Eur J Appl Physiol Occup Physiol. 1999 Mar;79(4):360-6. doi: 10.1007/s004210050521.
Thermal stress is known to impair endurance capacity during moderate prolonged exercise. However, there is relatively little available information concerning the effects of thermal stress on the performance of high-intensity short-duration exercise. The present experiment examined human power output during repeated bouts of short-term maximal exercise. On two separate occasions, seven healthy males performed two 30-s bouts of sprint exercise (sprints I and II), with 4 min of passive recovery in between, on a cycle ergometer. The sprints were performed in both a normal environment [18.7 (1.5) degrees C, 40 (7)% relative humidity (RH; mean SD)] and a hot environment [30.1 (0.5) degrees C, 55 (9)% RH]. The order of exercise trials was randomised and separated by a minimum of 4 days. Mean power, peak power and decline in power output were calculated from the flywheel velocity after correction for flywheel acceleration. Peak power output was higher when exercise was performed in the heat compared to the normal environment in both sprint I [910 (172) W vs 656 (58) W; P < 0.01] and sprint II [907 (150) vs 646 (37) W; P < 0.05]. Mean power output was higher in the heat compared to the normal environment in both sprint I [634 (91) W vs 510 (59) W; P < 0.05] and sprint II [589 (70) W vs 482 (47) W; P < 0.05]. There was a faster rate of fatigue (P < 0.05) when exercise was performed in the heat compared to the normal environment. Arterialised-venous blood samples were taken for the determination of acid-base status and blood lactate and blood glucose before exercise, 2 min after sprint I, and at several time points after sprint II. Before exercise there was no difference in resting acid-base status or blood metabolites between environmental conditions. There was a decrease in blood pH, plasma bicarbonate and base excess after sprint I and after sprint II. The degree of post-exercise acidosis was similar when exercise was performed in either of the environmental conditions. The metabolic response to exercise was similar between environmental conditions; the concentration of blood lactate increased (P < 0.01) after sprint I and sprint II but there were no differences in lactate concentration when comparing the exercise bouts performed in a normal and a hot environment. These data demonstrate that when brief intense exercise is performed in the heat, peak power output increases by about 25% and mean power output increases by 15%; this was due to achieving a higher pedal cadence in the heat.
已知热应激会损害适度长时间运动期间的耐力。然而，关于热应激对高强度短时间运动表现影响的可用信息相对较少。本实验研究了重复进行短期最大运动时的人体功率输出。在两个不同的时间段，七名健康男性在自行车测力计上进行了两组30秒的冲刺运动（冲刺I和冲刺II），每组之间有4分钟的被动恢复时间。冲刺运动分别在正常环境[18.7（1.5）摄氏度，相对湿度（RH）40（7）%]和炎热环境[30.1（0.5）摄氏度，RH 55（9）%]下进行。运动试验的顺序是随机的，且至少间隔4天。在对飞轮加速度进行校正后，根据飞轮速度计算平均功率、峰值功率和功率输出的下降情况。与正常环境相比，在炎热环境中进行运动时，冲刺I[910（172）瓦对656（58）瓦；P<0.01]和冲刺II[907（150）瓦对646（37）瓦；P<0.05]的峰值功率输出均更高。与正常环境相比，在炎热环境中冲刺I[634（91）瓦对510（59）瓦；P<0.05]和冲刺II[589（70）瓦对482（47）瓦；P<0.05]的平均功率输出也更高。与正常环境相比，在炎热环境中运动时疲劳速度更快（P<0.05）。在运动前、冲刺I后2分钟以及冲刺II后的几个时间点采集动脉化静脉血样本，以测定酸碱状态、血乳酸和血糖。运动前，不同环境条件下的静息酸碱状态或血液代谢物无差异。冲刺I和冲刺II后，血液pH值、血浆碳酸氢盐和碱剩余均降低。在两种环境条件下进行运动时，运动后酸中毒程度相似。不同环境条件下运动的代谢反应相似；冲刺I和冲刺II后血乳酸浓度升高（P<0.01），但比较在正常环境和炎热环境中进行的运动回合时，乳酸浓度无差异。这些数据表明，在炎热环境中进行短暂剧烈运动时，峰值功率输出增加约25%，平均功率输出增加15%；这是由于在炎热环境中实现了更高的踏频。
