Effects of environmental factors on heat tolerance during exercise.

为了研究运动过程中环境因素对热耐受性的影响，我们进行了以下三个实验。我们研究了适度运动后短暂的腿部冷却对后续高温运动心肺反应的影响。7名男性受试者在35℃（例1）条件下进行40分钟的测力计循环（达到峰值吸氧量的65%）后，将腿浸入35℃（对照条件：CONT）或20℃（冷却条件：COOL）水中5分钟，然后重复循环（和以前一样，但持续10分钟）（例2）。结果表明，在恢复期短暂的腿部冷却可以有效地减少后续高温运动中的热负荷和心肺负荷。我们研究了环境因素是否会影响运动时的耐热性。16名学生在高温条件下进行锻炼，研究这些生理参数、家乡气候条件和空调使用情况之间的关系。他们的热耐受性指标如前臂出汗率和皮肤血流量增加率与气候数据之间的关系趋于显著，说明家乡气候可能影响学生的热耐受性。我们测试了一个假设，即在高温下长时间运动时，核心温度的升高，而不是皮肤温度的升高，导致了分钟通气量（VE）的增加。13名受试者穿着与水熔合在10℃（T10）、35℃（T35）或45℃（T45）的宇航服，在循环测力仪上以峰值摄氧量的50%运动60分钟。结果表明，在高温下进行长时间的次极限运动时，VE随核心温度升高而升高，不受皮肤温度或核心温度升高速率的影响。

We aimed to investigate the effects of environmental factors on heat tolerance during exercise and conducted the following three experiments.1.We investigated the effects of brief leg cooling after moderate exercise on the cardiorespiratory responses to subsequent exercise in the heat. Following 40 min of ergometer cycling (65% of peak O_2 uptake) at 35℃ (Ex.1), seven male subjects immersed their legs in 35℃ (control condition:CONT) or 20℃ (cooling condition:COOL) water for 5 min and then repeated the cycling (as before, but for 10 min) (Ex.2). The results suggest that brief leg cooling during the recovery period may be effective at reducing thermal and cardiorespiratory strain during subsequent exercise in the heat.2.We investigated whether the environmental factors affect the heat tolerance during exercise. Sixteen students exercised in the heat and the relationships among those physiological parameters, the climate conditions of their home towns and the usage of air-conditioner. The relationships between their heat tolerance index such as the sweat rate and increase rate of skin blood flow in the forearm and the climate data tend to be significant, suggesting the climate of the home town could affect the heat tolerance in the students.3.We tested the hypothesis that during prolonged exercise in the heat, an increase in core temperature, not skin temperature, mediates an increase in minute ventilation (VE). Thirteen subjects exercised for 60 min on a cycle ergometer at 50% of peak oxygen uptake while wearing a suit per fused with water at 10℃ (T10), 35℃ (T35) or 45℃ (T45). The results suggest that during prolonged sub-maximal exercise in the heat, VE increases with core temperature and is unaffected by skin temperature or the rate at which core temperature increases.