Effects of environmental factors on heat tolerance and mechanism underlining hyperthemic hyperventilation.

我们的目的是研究环境因素对耐热性的影响，并阐明人类高温过度通气的机制。我们测试了这样一个假设，即在人类中，休息时引起的高热呼吸与在次最大、中等强度运动时引起的高热呼吸不同。这表明，高温呼吸确实取决于一个人是在休息还是在次最大、中等强度的运动中。我们测试了一个假设，即在人类中，运动-热适应（6天）会改变高温运动时的高热性呼吸。结果表明，热适应不影响高热性呼吸急促，但能显著增强运动时皮肤血管舒张反应。我们检验了高温过度通气部分反映了化学受体通气0_2驱动增强的假设，由此产生的低碳酸血症减弱了通气反应和/或降低了静息时大脑动脉平均血流速度。结果表明，在静息状态下，虽然热疗增加了化学感受器通气0_2驱动，但化学感受器通气0_2驱动对高热过度通气的相对贡献很小（约20%），且随着核心温度的升高而保持不变；热疗过度通气引起的低碳酸血症减少脑血流量，但不减少通气反应。我们研究了环境因素是否会影响运动时的耐热性。14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。汗液量、前臂皮肤血流量增加率、分钟通气量增加率等热耐受性指标与气候数据之间的关系不显著，说明最近的生活方式（包括空调和运动经历）可以覆盖家乡气候对学生热耐受性的影响。少

We aimed to investigate the effects of environmental factors on heat tolerance and to elucidate the mechanisms underlining the hyperthermic hyperventilation in humans.1. We tested the hypothesis that, in humans, hyperthermic hyperpnea elicited in resting subjects differs from that elicited during submaximal, moderate intensity exercise. It was suggested that hyperthermic hyperpnea does indeed differ depending upon whether one is at rest or exercising at submaximal, moderate intensity.2. We tested the hypothesis that, in humans, exercise-heat acclimation (6-days) changes the hyperthermic hyperpnea during exercise in the heat. It was suggested that heat acclimation does not affect the hyperthermic hyperpnea, although it markedly enhances the cutaneous vasodilatory response during exercise.3. We tested the hypothesis that hyperthermic hyperventilation in part reflects enhanced chemoreceptor ventilatory 0_2 drive, and that the resultant hypocapnia attenuates ventilatory responses and/or mi … More ddle cerebral artery mean blood velocity in resting humans. It was suggested that, in resting humans, although hyperthermia increases chemoreceptor ventilatory 0_2 drive, the relative contribution of the chemoreceptor ventilatory 0_2 drive to hyperthemic hyperventilation is small (〜20%) and unchanged with increasing core temperature, and hypocapnia induced by hyperthermic hyperventilation reduces cerebral blood flow but not ventilatory responses.4. We investigated whether the environmental factors affect the heat tolerance during exercise. Fourteen 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, increase rate of skin blood flow in the forearm, the increase rate of minute ventilation and the climate data were not significant, suggesting that the recent life style including air conditioning and exercise experience could override the effects of climate of the home town on the heat tolerance in the students. Less