How do I handle running in the heat?

As the sun beats down and temperatures soar, many runners find themselves facing a unique set of challenges when it comes to their training and racing. Running in the heat can be a real test of endurance and resilience, but with the right strategies, you can not only handle it but also perform at your best. In this blog post, we'll explore the physiological effects of running in the heat, the performance impacts it can have, and how heat adaptation and managing hydration can make those scorching runs feel a little more manageable.

Why does running in the heat feel so tough?

When you hit the pavement on a hot day, your body faces the task of regulating its core temperature. As your muscles exert themselves, they produce heat, which, in cooler climates, can be advantageous. However, as temperatures soar, your body must efficiently remove this surplus heat. This is achieved through various processes, including an uptick in blood flow to the skin and sweat evaporation. Yet, these processes may be strained under extreme heat, compounded by factors such as direct sunlight, high humidity, minimal wind, and inappropriate attire, all of which can lead to an increase in core body temperature.

This escalation in temperature places additional burdens on your cardiovascular system, increases use of muscle glycogen (carbs, fuel), and heightens the risk of heat-induced illness like heat exhaustion or heatstroke. Moreover, heat can impair gastrointestinal function, causing discomfort, and increase the perceived exertion, making runs feel more strenuous.

Running in temperatures exceeding 25°C, particularly when combined with over 70% humidity, can markedly diminish performance. Endurance for distances beyond 800 metres tends to suffer in these hot conditions, mainly due to the hampered sweat evaporation and suboptimal heat release, which is made worse by non-breathable garments.

Why should I heat adapt?

However, all hope is not lost when it comes to conquering the heat. Your body has a remarkable ability to adapt to warm conditions, and these adaptations can make your hot-weather runs more manageable. This process is known as heat adaptation or acclimation. It's closely linked to your prior heat exposures and current fitness level.

As you gradually increase your run duration and heat exposure, your body becomes better equipped to handle the heat. Within just a week of training in warm conditions, your blood plasma volume expands, providing more fluid for sweating without leading to dehydration. This expansion allows for more efficient cooling. Your body also learns to sweat earlier in your run, increasing sweat rates and becoming less salty to conserve sodium. Your heart rate even slows down slightly, optimising blood circulation between beats, ensuring an adequate supply to both your skin and muscles.

Moreover, your perception of effort in hot weather running begins to change, making those initially gruelling runs feel less challenging over time. The adaptation process can result in significant performance improvements, with time to exhaustion trials showing potential increases of up to approximately 23%, and time trials demonstrating a boost of around 7% following heat acclimation. Surprisingly, this adaptation can even enhance aerobic performance in cooler conditions by up to 6% without any negative effects.

If you will be training and/or racing in the heat and want your best performance, heat adaptation should be part of your schedule. For those who do not live in warm-hot climates, there are methods of artificial heat adaptation that can prepare you well to cope and perform well when running in the heat.

How do I manage hydration when running in the heat?

One critical aspect of running in the heat is managing your hydration. Staying adequately hydrated is essential for both shorter and longer races. To prevent dehydration and maintain peak performance, understanding your sweat rate and planning your fluid intake accordingly is crucial. Some athletes may require additional sodium for events lasting longer than 4 hours to maintain electrolyte balance.

Training yourself to drink more fluids can also be beneficial. Many runners are not accustomed to consuming enough liquids, so increasing your fluid intake, especially in hot conditions, can be essential in preventing dehydration.

Summary

Running in the heat can be a daunting challenge, but with the right strategies, you can not only handle it but thrive in warm weather conditions. Understanding the physiological effects of heat on your body, the performance impacts, the benefits of heat adaptation and managing hydration are crucial for any runner tackling high temperatures.

If you're training and racing in the heat, I'm here to assist you! As an Accredited Sports Dietitian, I can provide you with a range of strategies that will not only make running in the heat more comfortable but also optimise your performance as the temperature rises. With personalised guidance, you can maximise your training in hot conditions and reach your running potential, no matter how high the mercury climbs. So, stay cool, stay hydrated, and let's work together to keep you running strong and achieving your goals!

To book a performance strategy call to discuss the exact steps to perform at your best for your next big event click here!

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References

Heathcote et al 2018, 'Passive heating: reviewing practical heat acclimation strategies for endurance athletes', Frontiers in Physiology, vol. 9, article 1861.

Lorenzo et al 2010, 'Heat acclimation improves exercise performance', J Appl Physiol, vol. 109, iss. 4, pp. 1140–1147.

McCubbin et al 2020, 'Sports Dietitians Australia Position Statement: Nutrition for Exercise in Hot Environments', International Journal of Sport Nutrition and Exercise Metabolism, vol. 30, pp. 83-98.

Periard, Eijsvogels & Daanen 2021, 'Exercise under heat stress: Thermoregulation, hydration, performance implications and mitigation strategies', Physiological Reviews, vol. 101, pp.1873-1979.

Pryor et al 2019, 'Application of evidence-based recommendations for heat acclimation: Individual and team sport perspectives', Temperature, vol. 6, no. 1, pp. 37-49.

Tyler et al 2016, 'The effects of heat adaptation on physiology, perception and exercise performance in the heat: a meta-analysis', Sports Med, vol. 46, iss. 11, pp. 1699–1724.