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Tuesday, June 21, 2011

CAN WE DEFEND HYPERTHERMIA AND DEHYDRATION IN FOOTBALL?


Are hyperthermia and dehydration causes of fatigue in football? Yes, they are when match or training is performed in a warm environment.

WHAT IS A WARM ENVIRONMENT? It is the combination of dry temperature and relative humidity that cause thermal stress to the human body. Generally, a warm environment is defined at a temperature higher than 28 oC with moderate relative humidity. At this environment, fatigue arrives before muscle glycogen and blood glucose are lowered below a critical level.

WHAT IS THE MECHANISM OF FATIGUE IN SUCH ENVIRONMENT? Players sweat a lot for thermoregulation. This results in body fluids loss and, if not replaced, to dehydration. Dehydration and thermal stress due to the warm environment result in inside body temperature elevation. When body’s core temperature becomes higher than 38.5 oC in non-elite and higher than 39 oC in elite players, physical and mental performance decline. Indeed, studies in football players show that both distance covered and skill performance decline with hyperthermia and dehydration.

Studies with brain scanning techniques show that hyperthermia negatively affects blood supply and function of certain areas of the brain that are associated with motor unit recruitment and decision-making. Based on this indirect evidence, it is reasonable to speculate that hyperthermia might affect technical and tactical decisions during the match in football players.

SIMPLE MEASURES TO AVOID OR RETARD HYPERTHERMIA AND DEHYDRATION
  1. Avoid training during the warm hours of day.
  2. Adopt pre-cooling strategies before training/match and in half time. In the literature, several strategies are proposed like cold water immersion, ice placement on the legs, cooling vests.
  3. Drink as much fluid as you can before and during training/matches. Fluid taken should not exceed losses due to sweating. Fluids should be isotonic with a low carbohydrate concentration (2-5%). Water drinking is also effective in minimizing dehydration and hyperthermia.
  4. Acclimatization to heat will alleviate the symptoms in 3-10 days.
  5. Response to playing and training in the heat is different from player to player.

For more reading
Grantham et al. Scand J Med Sci Sports Suppl 3: 161-167, 2010
McGregor et al. J Sports Sci 17:895-903, 1999
Nassis & Geladas. Eur J Appl Physiol 88:227-233, 2002

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