Kenny Glen P, Dorman Lucy E, Webb Paul, Ducharme Michel B, Gagnon Daniel, Reardon Francis D, Hardcastle Stephen G, Jay Ollie
Laboratory of Human Bioenergetics and Environmental Physiology, School of Human Kinetics, University of Ottawa, Ottawa, Ontario, Canada.
Med Sci Sports Exerc. 2009 Mar;41(3):588-96. doi: 10.1249/MSS.0b013e31818c97a9.
The aim of this study was to investigate heat balance during thermal transients caused by successive exercise bouts. Whole-body heat loss (H x L) and changes in body heat content (Delta Hb) were measured using simultaneous direct whole-body and indirect calorimetry.
Ten participants performed three successive bouts of 30-min cycling (Ex1, Ex2, and Ex3) at a constant rate of heat production of approximately 500 W, each separated by 15-min rest (R1, R2, and R3) at 30 degrees C.
Despite identical rates of heat production during exercise, the time constant (tau) of the exponential increase in H x L was greater in Ex1 (tau = 12.3 +/- 2.3 min) relative to both Ex2 (tau = 7.2 +/- 1.6 min) and Ex3 (tau = 7.1 +/- 1.6 min) (P < 0.05). Delta Hb during Ex1 (256 +/- 76 kJ) was greater than during Ex2 (135 +/- 60 kJ) and Ex3 (124 +/- 78 kJ) (P < 0.05). During recovery bouts, heat production was the same, and the tau of the exponential decrease in H L was the same during R1 (tau = 6.5 +/- 1.1 min), R2 (tau = 5.9 +/- 1.3 min), and R3 (tau = 6.0 +/- 1.2 min). Delta Hb during R1 (-82 +/- 48 kJ), R2 (-91 +/- 48 kJ), and R3 (-88 +/- 54 kJ) were the same. The cumulative Delta Hb was consequently greater at the end of Ex2 and Ex3 relative to the end of Ex1 (P < 0.05). Likewise, cumulative Delta Hb was greater at the end of R2 and R3 relative to R1 (P < 0.05).
The proportional decrease in the amount of heat stored in the successive exercise bouts is the result of an enhanced rate of heat dissipation during exercise and not due to a higher rate of heat loss in the recovery period. Despite a greater thermal drive with repeated exercise, the decline in the rate of total heat loss during successive recovery bouts was the same.
本研究旨在调查连续运动回合引起的热瞬变期间的热平衡。使用同步直接全身量热法和间接量热法测量全身热损失（H x L）和身体热含量变化（ΔHb）。
10名参与者以约500W的恒定产热速率进行了三轮连续30分钟的骑行（Ex1、Ex2和Ex3），每轮之间在30摄氏度下休息15分钟（R1、R2和R3）。
尽管运动期间产热速率相同，但Ex1中H x L指数增加的时间常数（τ）（τ = 12.3 ± 2.3分钟）相对于Ex2（τ = 7.2 ± 1.6分钟）和Ex3（τ = 7.1 ± 1.6分钟）更大（P < 0.05）。Ex1期间的ΔHb（256 ± 76 kJ）大于Ex2（135 ± 60 kJ）和Ex3（124 ± 78 kJ）期间（P < 0.05）。在恢复回合期间，产热相同，并且R1（τ = 6.5 ± 1.1分钟）、R2（τ = 5.9 ± 1.3分钟）和R3（τ = 6.0 ± 1.2分钟）期间H L指数下降的τ相同。R1（-82 ± 48 kJ）、R2（-91 ± 48 kJ）和R3（-88 ± 54 kJ）期间的ΔHb相同。因此，相对于Ex1结束时，Ex2和Ex3结束时的累积ΔHb更大（P < 0.05）。同样，相对于R1，R2和R3结束时的累积ΔHb更大（P < 0.05）。
连续运动回合中储存热量的比例下降是运动期间散热速率提高的结果，而不是由于恢复期更高的热损失速率。尽管重复运动时热驱动力更大，但连续恢复回合期间总热损失速率的下降是相同的。
