Centre de Recherche Cardio-Thoracique de Bordeaux, U1045, Univ. Bordeaux, 33000, Bordeaux, France,
Eur J Appl Physiol. 2013 Oct;113(10):2587-94. doi: 10.1007/s00421-013-2696-6. Epub 2013 Jul 23.
Challenging environmental conditions including heat and humidity are associated with particular risks to the health of runners and triathletes during prolonged events. The heat production of a runner is the product of its energy cost of running (C r) by its velocity. Since C r varies greatly among humans, those individuals with high C r are more exposed to heat stress in warm and humid conditions. Although risk factor awareness is crucial to the prevention of heat stroke and potential fatalities associated therewith, how C r affects the highest sustainable velocity (V) at which maximal heat loss matches heat production has not been quantified to date.
Here, we computed in virtual runners weighting 45-75 kg, the influence of C r variability from 3.8 to 4.4 J·m(-1)·kg(-1) on V. Heat loss by radiation, convection, and conduction was assessed from known equations including body dimensions, running velocity (3.4-6.2 m·s(-1)), air temperature (T a, 10-35 °C) and relative humidity (r h, 50, 70 and 90 %).
We demonstrated a marked and almost linear influence of C r on V in hot and humid conditions: +0.1 J·kg(-1)·m(-1) in C r corresponded to -4 % in V. For instance, in conditions 25 °C r h 70 %, 65-kg runners with low C r could sustain a running speed of 5.7 m·s(-1) as compared to only 4.3 m·s(-1) in runners with high C r, which is huge.
We conclude that prior knowledge of individual C r in athletes exposed to somewhat warm and humid environments during prolonged running is one obvious recommendation for minimizing heat illness risk.
在长时间的运动中，炎热和潮湿等具有挑战性的环境条件会对跑步者和三项全能运动员的健康造成特殊风险。跑步者的热量产生是其跑步能量成本（C r）与其速度的乘积。由于人类之间的 C r 差异很大，因此那些 C r 较高的人在温暖和潮湿的条件下更容易受到热应激的影响。尽管风险因素意识对于预防中暑和相关的潜在致命性至关重要，但到目前为止，还没有量化 C r 如何影响最大可持续速度（V），即最大散热与产热相匹配的速度。
在这里，我们在体重为 45-75kg 的虚拟跑步者中计算了 C r 从 3.8 到 4.4J·m(-1)·kg(-1)的变化对 V 的影响。通过已知的方程评估了辐射、对流和传导的散热，这些方程包括身体尺寸、跑步速度（3.4-6.2m·s(-1)）、空气温度（T a，10-35°C）和相对湿度（r h，50、70 和 90%）。
我们在炎热和潮湿的条件下证明了 C r 对 V 的显著且几乎线性的影响：C r 每增加 0.1J·kg(-1)·m(-1)，V 就会降低 4%。例如，在 25°C r h 70%的条件下，低 C r 的 65 公斤跑步者可以维持 5.7m·s(-1)的跑步速度，而高 C r 的跑步者只能维持 4.3m·s(-1)的速度，这是巨大的差异。
我们的结论是，在长时间跑步过程中，运动员在暴露于有点温暖和潮湿的环境中时，预先了解个人的 C r 是降低热疾病风险的一个明显建议。
