How Heat Affects Your Body During Exercise

Pushing your limits has no official season, but the summer heat can quickly humble even the most dedicated athlete. As the mercury rises, it’s essential to understand how heat impacts your physiology during exercise, so you can stay on top of your game despite the scorching temperatures.

Heat’s Effect on Physiology

When you exercise in extreme heat, your body’s physiological systems experience widespread effects, leading to decreased performance and increased fatigue. Below are some of the critical ways heat affects your physiology during exercise:

• The rate of muscle glycogen depletion accelerates, further compromising energy availability.
• Muscle blood flow decreases, reducing oxygen and nutrient delivery to exercising muscles.
• Cardiac output decreases, exacerbating exercise-induced fatigue and compromise cardiovascular performance.
• The sweat rate is not sufficient, compromising thermal regulation and increasing body temperature.
• Perceptual heat stress increases, intensifying psychological discomfort and decreasing physical performance.
• Lower VO2 max: Heat stress is a strong predictor of decreased aerobic fitness, significantly impacting endurance-based sports and activities.

Data indicates that temperatures above 77°F (25°C) typically result in decreased athletic performance, with impaired hydration and acclimatization heightening the risk of heat illness. Even when humidity is factored into the equation, the body’s ability to thermoregulate remains drastically affected, leading to a loss in functional capacity.

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Potential Risks of Heat-Related Training

Miscalculating the impact of heat on performance can lead to adverse outcomes. Potential risks of unprepared training in heat include:

• Increased risk of heat-related illnesses like muscle cramps, heat exhaustion, heat stroke, and even coma.

Raising your body temperature above safe levels without proper acclimation and adaptation can have debilitating effects. It’s crucial to appreciate the relationship between heat, exercise intensity, and personal tolerance to maximize safety during workouts.

Strategies for Heat-Aware Training

Heat Adaptation Regimen

Becoming adapted to high-temperature environments improves the body’s thermoregulation abilities and boosts tolerance to heat-induced discomfort. Engage in a strategically planned exposure to heat (HAP) for 1-2 weeks to elicit significant enhancements in thermoregulation and cardio performance. Extend the regimen’s duration to attain optimal benefits for acclimation.

• Train in short, 30-minute segments during the first 5-6 hours in the heat, gradually increase session length and intensity (Tyler et al., 2016).
• Expose yourself to temperature conditions that best approximate worst-case scenarios (Tyler et al., 2016).

Preparation Tips

• Plan ahead by consuming adequate fluids and electrolyte-rich snacks to maintain hydration levels throughout exercise and recovery.
• Weigh yourself, observe fluid intake, and adapt attire, accessories, and strategies according to humidity and temperature conditions to mitigate performance decrements and fatigue (Pryor et al., 2018).

Mindfulness and Adaptation

Don’t risk excessive heat exposure. Allow yourself ample time to adapt to increasingly high temperatures during workouts. Gradually increment the length and intensity of each training session.

Moderate your pace when confronted with extreme heat, making allowances for factors like humidity. If feasible, incorporate heat sessions or cardio activities in a comfortable setting or during cooler months. It is essential to prioritize your personal heat safety and adaptability strategies based on your specific needs.

Sources

1. Tyler CJ, Reeve T, Hodges GJ, Cheung SS. The effects of heat adaptation on physiology, perception, and exercise performance in the heat: a meta-analysis. Sports Medicine. 2016; 46(11): 1699-1724.
2. Waldron M, Fowler R, Heffernan S, Tallent J, Kilduff L, Jeffries O. Effects of heat acclimation and acclimatization on maximal aerobic capacity compared to exercise alone in both thermoneutral and hot environments: A meta-analysis and meta-regression. Sports Medicine. 2021; 51(7): 1509-1525.
3. Pryor JL, Johnson EC, Roberts WO, Pryor RR. Application of evidence-based recommendations for heat acclimation: individual and team sport perspectives. Temperature (Austin). 2018; 6(1): 37-49.