Episode 18 - When the Heat Steals Your Pace - How to Train Smart on Hot Days

This episode explains why running performance drops in hot conditions and why it is not simply a loss of fitness or lack of toughness. In the heat, the body has two jobs: keep running and protect itself from overheating. More blood is directed towards the skin for cooling, sweat rate increases, heart rate rises, and the same pace costs more energy.

The key message is that on hot days, effort matters more than pace. A pace that feels easy in cool weather may become moderate or hard in the heat. Trying to force normal pace often leads to overheating, dehydration, gut problems, and a major slowdown later.

If a hot race is expected, heat acclimation over 10–14 days can improve tolerance. But when a heatwave arrives suddenly, the goal is damage control: slow down early, reduce intensity, walk climbs sooner, use shade, cool aggressively, hydrate sensibly, and protect the gut.

Main takeaway: In the heat, do not fight for your normal pace. Manage your effort, stay cool, and slow down before your body forces you to slow down.

Key references:

• González-Alonso, J. 2007. The cardiovascular challenge of exercising in the heat. Journal of Physiology.
• Wingo, J. E., Ganio, M. S., & Cureton, K. J. 2012. Cardiovascular drift during heat stress: implications for exercise prescription. Exercise and Sport Sciences Reviews.
• Périard, J. D., Eijsvogels, T. M. H., & Daanen, H. A. M. 2021. Exercise under heat stress: thermoregulation, hydration, performance implications, and mitigation strategies. Physiological Reviews.
• Racinais, S. et al. 2015. Consensus recommendations on training and competing in the heat. Scandinavian Journal of Medicine & Science in Sports.
• Racinais, S. et al. 2023. IOC consensus statement on recommendations and regulations for sport events in the heat. British Journal of Sports Medicine.
• Heathcote, S. L. et al. 2018. Reviewing practical heat acclimation strategies for endurance athletes. Frontiers in Physiology.
• Zurawlew, M. J. et al. 2018. Post-exercise hot water immersion elicits heat acclimation adaptations in endurance trained and recreationally active individuals. Frontiers in Physiology.
• Wierick, S. C. et al. 2025. Hydration Strategies in Ultra-Endurance Running. Sports Medicine - Open / PMC.
• Knechtle, B. et al. 2019. Exercise-associated hyponatremia in endurance and ultra-endurance performance. Medicina.
• Hoffman, M. D. et al. 2015. Sodium Intake During an Ultramarathon Does Not Prevent Muscle Cramping, Dehydration, Hyponatremia, or Nausea. Sports Medicine - Open.