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Heat, Humidity and Heartbreak- the effects that heat has on athletes.

Athletics and Rugby- Heating up.

Heat and humidity has become a hot topic (excuse the pun) with the Rugby World Cup taking place in Japan conditions proved challenging for players to contend. Over the weekend, the spotlight was firmly on the Ireland side defeated by both Japan’s humid conditions and by the team themselves, who were better acclimated.

At the same time, the World Athletics Championships were deemed a disaster (and dangerous) in Qatar, with desert temperature pushing even the most conditioned athletes to the edge. 28 athletes of the 68 female competitors in the marathon at the World Athletics Championships in Doha did not finish. There was a make-shift hospital set up at the event to deal with the casualties. The marathon began at midnight to try and reduce the deleterious impact of heat, however, questions are being asked of the organisers who let events proceed despite potentially life threatening conditions.

Looks of exhaustion, overheating and disappointment from the Irish

When it comes to acclimatization, and specifically managing heat, sports scientists become an integral part of the support team preparing both teams and individuals for the strain that heat will place on the body.

The Effects of Heat.

Heat and humidity lead to specific physiological challenges for the athlete; dehydration, decreased blood volume and increased core body temperature (hyperthermia). In states of hyperthermia, the ability for muscle to contract is decreased and athletes fatigue at an increased rate. High core temps also cause a shift in energy production from aerobic to anaerobic mechanisms, which means the body has to use up its muscle energy stores more rapidly. 

Unfortunately, during a longer athletic event, the rate of adding energy (sports drinks, energy bars, gels, etc) can’t keep up with the rate of losing energy when heat and humidity are high. Similarly, when the core body temperature rises and blood volume decreases, the peripheries causing swelling.heart cannot pump blood efficiently and blood can pool in the

In states of dehydration athletes can lose between 2-8% body weight, this results in decreased aerobic and anaerobic capacity. A key consideration for the sports science team at the World Cup and the World Championships will be monitoring the % body weight lost due to dehydration and restoring hydration safely before the next round. Typically, hydration strategies begin before events and continue for days after the event.


Heat related symptoms that the athletes and players will be facing include heat cramps due to altered electrolyte balance (specifically sodium, chloride and potassium) due to excessive or increased fluid loss. Heat exhaustion symptoms occur when hyperthermia results in the athlete losing the ability to regulate temperature, this can occur when body temperature exceeds 39 degrees Celsius, athletes will appear pale, clammy and confused (obviously not ideal for performance!).

Finally, heat stroke occurs when the body temperature exceeds 41 degrees Celsius and the ability to regulate temperature has failed, the body can no longer sweat (to cool itself). Athletes appear red and flushed and delirious, in extreme cases heat stroke can lead to permanent physiological damage.

Prevention and Preparation.

Fortunately, extreme conditions are now well understood by sports support teams and athletes are usually well prepared to deal with the extra demands placed on them during performance in hot or humid environments. Acclimatization can occur quickly (7-10 days) and it is a process that is carefully planned and considered in the preparation for major championships. If you are interested in learning more about the physiological preparation of athletes for extreme performance environments take a look at our range of Sports courses, designed to develop elite sports performance support staff, especially our Sports Science courses.

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