core body temperature · heat stress · heat stroke · overheating · sports ·

The Consequences of Overheating in Sports

Imagine the feeling of coming into the final sprint after hours of racing with difficult climbs against the harsh elements and other riders and you blow-up. In stage 9 of the 2020 Tour de France, Marc Hirschi of Team Sunweb did an incredible 80km breakaway only to be caught within the last three kilometers into Laruns. Hirschi still had some energy reserves to compete for the sprint-finish but sometimes athletes fall short. 

There are a lot of factors that can make-or-break an athlete in the midst of competition and core body temperature of these. Heat is intrinsically connected to physical effort and anything an athlete can do to cool down will help improve performance. 

How does core temperature regulation work?

The process of core temperature regulation, also known as homeostasis, is regulating the body to maintain a constant core temperature, and this optimal temperature varies from person to person. Between 36.5 and 37.5°C the human body functions optimally, yet when it gets under or over this range, then autonomic and behavioral responses are triggered to balance the heat surplus or loss. In other words, your body is designed to cope when core body temperature increases or decreases (Flouris, 2019, p.3).

For sports, it is usually the excess of heat that poses problems since physical exercise increases body temperature. Improving performance benefits from pushing our body to its limits. This thermal discomfort can be overcome and to help a motivated mind to break a record. But at the same time, neglecting core body temperature while racing can also have short-term and long-term consequences from collapsing through to damage that requires months of recovery. 

Sarah True, a former Olympic American Triathlete is a good example. Her focused mind overlooked the impact of her body temperature and at the Frankfurt Triathlon cost her a qualification into the heralded Kona IWC 2019. She was 7 minutes ahead of the second female runner, 30min ahead of the qualification requirement. Compounded by the extreme weather conditions (38°C) her CORE body temperature management had increased dangerously and just 700 meters from the finish line she collapsed and was not able to finish the race. 


Alistair Brownlee, 2x Olympic Gold Medalist, 2x ITU Triathlon World Champion, 3x EU Champion also collapsed only meters away from the finish line in London from heat stress. “With 400 meters to go, I was running in second place on the shoulder of big rival, Javier Gomez. That’s about the last thing I remember until I woke up on an emergency medical bed, covered in ice with wires and drip lines coming out of me.”

How does heat stress look like?

In the extreme cases, heat stress can be life-threatening, and this is known as Exertional Heat Stroke. It is characterized by central nervous system dysfunction such as delirium, agitation, inappropriate aggressiveness, convulsions and even coma.

Yuki Yamazaki suffering a heat stroke

In mild situations, referred to as Heat Exhaustion, the patient may experience fatigue, dizziness, headache, nausea, vomiting, hyperventilation and impaired cognition.

In a video following the Frankfurt Triathlon, Sarah True mentions how she had “hard time focusing”.  From a medical perspective, these symptoms are attributed to the “inability to sustain cardiac output to meet combined demands of increased skin blood flow for heat dissipation and blood flow for the metabolic requirements of exercising skeletal muscle and vital organs” (Laitano et al., 2019, p.93). In other words, the efforts required by the body to compensate the heat surplus takes over from resources for the body’s general functions.

While heat stroke convalescence (recovery) varies, a group of researchers from the Israeli Heller Institute of Medical Research Sheba Medical Center point out some “sporadic descriptions of disturbances that lasted for up to 4 months” (1993). Alistair Brownlee reportedly “didn’t feel right for months” following his heat stress collapse.

Extreme cold can also take its toll on athletes as well. The impairment of neural drive and complex cognitive task performance due to hyperthermia was documented by the Athlete Health and Performance Center from Doha together with the University of Canberra Research Institute for Sport an Exercise in Australia confirms the importance of monitoring and controlling those heat levels in any strategic sports (p.81). Beyond the immediate autonomic and behavioral thermoregulation, long-term acclimatization strategies may also be employed. 

The long-term health consequences associated with mild heat stress may be considered a low risk to overall health, in the short term, better awareness can help manage and prevent heat stress. While athletes may be more in-tune with the effect of heat in the summer radically changing weather conditions and the need to acclimatize increases the importance of managing heat and core body temperature during training, competition and recovery. 

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