by Jon Hearn

Created on: July 07, 2010

For any athlete running in extreme environmental conditions, such as a desert, will push the limits of their body. McArdle, Katch and Katch (2006) suggest under heat stress thermoregulation becomes more difficult. They state that high ambient temperatures reduce the effectiveness of the body to lose heat by conduction, convection and radiation. When this occurs water vaporisation from the respiratory tract and sweat evaporation become the only way for heat loss to occur. This will result in increased core temperatures and increases the likelihood of a dehydration related illness and injuries.  In a recent case study athletes ran two legs during through the Sahara desert. A night run which was warm, humid and had no solar radiation and a day run which was hot dry and had full solar radiation. Using temperature telemetry pills, Degroot and Kenney (2008) found that these athletes needed to run a slower pace during the day run to maintain a manageable core body temperature and avoid heat illness or injury. They also found, during the day run, even at the slower pace metabolic rate was higher and became more erratic.

The Marathon des Sables, held yearly in Morocco, is an example of a brutal competition where athletes need to be fully prepared and aware of heat stress. The 151 mile ultra-endurance race is unique as competitors must be self-sufficient and carry all their own food and equipment through out the 6 day event. They have strict limits to the amount of food (minimum of 1500kcals) and water (maximum of 9 litres) they can carry. The event takes place in a sandy, dry, hilly terrain with extreme temperatures of up to 50degC.

The objectives of this case study are to look at how an athlete can prepare for the hot conditions and the expected physiological changes that would occur from these recommendations.

According to McArdle, Katch and Katch (2006) heat acclimatisation before competition will incur several physiological changes. These effects focus on cooling the core body temperature. One way the body adapts is by producing more sweat earlier in exercise with a lower salt concentration and distributing this sweat more effectively over the body’s surface area. This maximises evaporative cooling and helps to preserve electrolytes in the extracellular fluid. Another expected adaptation is the improvement of cutaneous blood flow transporting some metabolic heat from deep tissue body’s shell resulting in the core body temperature also decreasing.

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