Athletes can beat the heat, even during an Australian summer

January 21, 2014 by Adam Trewin, The Conversation
Shifting hemispheres? A good training plan must include time to acclimatise. Credit: Vox Efx

Two of Australia's biggest international sporting events kicked off last week – the Australian Open in Melbourne and the Tour Down Under in Adelaide – coinciding with a heatwave over southeast Australia, where temperatures exceeded 40C for most of the week.

So is it really "inhumane" to hold sporting tournaments in ?

You may have seen reports of players and a ball boy fainting on court. Canadian tennis player Frank Dancevic hallucinated Snoopy before collapsing at Australian Open on Tuesday.

This year's Tour Down Under started in mild weather but the lead up was anything but. AAP/Dan Peled

Northern hemisphere athletes competing in Australia's summer require at least five to seven days of training in the to become adequately acclimatised after living in cold winter conditions (not great for cyclists training before the start of the Tour Down Under on Sunday).

Humans have a remarkable ability to tolerate hot conditions, but most heat stress related issues appear to be the result of inadequate acclimatisation to the conditions prior to competition.

We're not particularly energy efficient – only about 22% of the food energy we consume is used as biological "fuel" while the remainder is lost as heat. This is helpful for keeping us warm in cold conditions (a process called thermogenesis), but presents a challenge when the ambient temperature exceeds that of our internal temperature.

Because our bodies can only tolerate a core body temperature within a small window around 37C, we need to achieve heat loss via:

  • evaporation of sweat
  • radiation (infrared)
  • convection of heat to the air (such as a cool breeze)
  • conduction (such as sitting on a cold chair).

If you can't stand the heat …

Athletes who will be competing in high temperatures as well as high humidity must become acclimatised to exercising in the heat, or they risk impaired performance or more serious thermal stress injury.

After just a few days of training in the heat, adaptations begin to occur in the athlete. These include a lower sweat threshold (they begin sweating from a lower temperature, and sooner), an increased sweat maximal rate, increased plasma volume (the fluid component of blood) and decreased concentration of electrolytes (such as salts) within the sweat itself.

Other preventative measures for thermal injury are regular fluid intake and pre-cooling methods such as wearing ice vests and consuming ice-slushie drinks.

During competition

When we exercise, the rate of biochemical reactions in our bodies are greatly increased to supply energy to exercising muscles. As a result we also generate large amounts of heat, putting pressure on our heat loss mechanisms.

During exercise in high environmental temperatures, there are a range of responses which occur in the body. A region of the brain (hypothalamus) senses rising core and signals for sweat production to increase evaporative cooling and for blood flow to be diverted to the skin to benefit from those cooling effects.

The trade-off here is that this robs the working muscles of oxygen-rich blood flow and reduces exercise capacity. There is also a decrease of the plasma volume as exercise continues, meaning that blood flow to working muscles and other organs is further reduced. Dehydration can occur quickly if fluid intake doesn't match these fluid shifts and losses. Furthermore, perception of effort (such as fatigue) is increased as the central nervous system heats up, limiting exercise performance.

Cycling vs tennis

Different types of exercise also lead to different responses to heat. For example, road cyclists at this week's Tour Down Under will ride at a sustained moderate to high-intensity effort, whereas at the Australian Open perform many short bursts of intense movement.

While these two activities may therefore seem quite different, the average workloads are both very high and crucially may last for more than five hours at a time, meaning that there is a good opportunity for thermal gain to set in.

A major difference in the rate of thermal gain is that a cyclist travels at higher velocity through the air relative to a tennis players which is a major factor for heat loss ("windchill factor" – think of a gym class with fans on versus off).

So while exercise in the heat can be a challenge for the human body, with some time to adapt during training, it is still possible to perform (albeit at a reduced pace) even in the most searing of temperatures.

Explore further: Awareness is key to preventing heat- and cold-induced athletic injuries

Related Stories

Awareness is key to preventing heat- and cold-induced athletic injuries

December 3, 2012
Extreme heat or cold can cause dangerous and potentially fatal side effects in athletes. A literature review appearing in the December 2012 issue of the Journal of the American Academy of Orthopaedic Surgeons (JAAOS) provides ...

Tips for safe winter workouts

December 22, 2013
(HealthDay)—If you exercise outdoors during the winter, be sure to do so safely, an expert says.

Older firefighters may be more resilient to working in heat

January 8, 2014
Older firefighters who are chronically exposed to heat stress on the job could be more heat resilient over time. A recent study published in the December issue of the Journal of Occupational and Environmental Hygiene (JOEH) ...

Paracetamol improves exercise endurance in the heat

September 19, 2013
Paracetamol has a significant effect on exercise performance and the body's ability to cope with the thermal challenge of exercise in the heat, shows a study published today [20 September] in Experimental Physiology.

Beat the heat: Exercise safety on hot summer days

June 22, 2012
(Medical Xpress) -- It’s already been one of the warmest years in decades and the 90-plus degree temperatures just keep coming. It’s always important to be conscious of weather conditions when you exercise, but ...

Recommended for you

Federal snack program does not yield expected impacts, researchers find

August 17, 2017
A well-intentioned government regulation designed to offer healthier options in school vending machines has failed to instill better snacking habits in a sample of schools in Appalachian Virginia, according to a study by ...

In a nutshell: Walnuts activate brain region involved in appetite control

August 17, 2017
Packed with nutrients linked to better health, walnuts are also thought to discourage overeating by promoting feelings of fullness. Now, in a new brain imaging study, researchers at Beth Israel Deaconess Medical Center (BIDMC) ...

Energy dense foods may increase cancer risk regardless of obesity status

August 17, 2017
Diet is believed to play a role in cancer risk. Current research shows that an estimated 30% of cancers could be prevented through nutritional modifications. While there is a proven link between obesity and certain types ...

Technology is changing Generation smartphone, and not always for the better

August 16, 2017
It's easy to imagine some graybeard long ago weighing in on how this new generation, with all its fancy wheels, missed out on the benefits of dragging stuff from place to place.

The environmental injustice of beauty

August 16, 2017
Women of color have higher levels of beauty-product-related chemicals in their bodies compared to white women, according to a commentary published today in the American Journal of Obstetrics and Gynecology. The authors say ...

Heavily used pesticide linked to breathing problems in farmworkers' children

August 15, 2017
Elemental sulfur, the most heavily used pesticide in California, may harm the respiratory health of children living near farms that use the pesticide, according to new research led by UC Berkeley.


Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.