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Published Jun 27, 2024

s4/e23: Heat Series Part 1: Why Running in the Heat Slows You Down So Much

Coach Elisabeth Scott delves into the science of thermoregulation and hydration, explaining how they impact running performance in high temperatures. She offers valuable insights and strategies to combat the performance decline and health risks associated with heat, enhancing runners' understanding of heat adaptation and hydration management.
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  • Environmental Impact

    Running in hot weather presents unique challenges due to various environmental factors such as temperature, humidity, air velocity, and solar radiation. explains that these elements interact in complex ways, affecting performance differently depending on their combination 1. For instance, high humidity can prevent sweat from evaporating, hindering the body's ability to cool down 2. This can lead to increased thermal strain, making it essential for runners to adjust their expectations and pace accordingly 3.

    It's not a true representation of your fitness. It's just hot.

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    Understanding these factors helps runners manage their performance and avoid unnecessary stress about their fitness levels.

       

    Heat Stroke Risks

    Exertional heat stroke is a serious risk for runners in hot conditions, being the third leading cause of death among athletes in the U.S. 4. emphasizes the importance of recognizing symptoms like the cessation of sweating, which requires immediate action to prevent life-threatening consequences 4. She advises runners to be vigilant about their hydration and pace, especially during races in hot weather, to avoid creating a "perfect storm" for heat stroke 5.

    It's not you, it's the heat.

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    By understanding these risks, runners can take proactive measures to protect themselves.

       

    VO2 Max Effects

    Running in heat significantly impacts VO2 max, a crucial measure of aerobic performance. explains that heat causes physiological changes, such as increased heart rate and vasodilation, which can lower VO2 max temporarily 6. Dehydration exacerbates this effect, with studies showing up to a 21% reduction in VO2 max under extreme conditions 7.

    The environmental conditions that is dry versus humid led to a similar decrease in VO2 max, which was more pronounced when hypo hydrated.

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    To mitigate these effects, runners should consider personalized hydration strategies, balancing between drinking to thirst and following a schedule 8.

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