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TRAINING AND RACING IN HEAT AND HUMIDITY

Heat, often combined with humidity (depending on where you live) during the summer months, can have a dramatic impact on training and competition. You may not end up being taken to the hospital or collapsing before the finish line due to dehydration (although this can and does happen), but your performance during a race, and the quality of your training can be negatively influenced by the effects of heat and humidity. Sweat rates can increase up to 2-3 times in hot conditions, the risk of developing a heat illness increases dramatically, and the body processes nutrients differently when the temperature rises.

Understanding some basic principles regarding the physiology of exercise in hot/humid conditions can help you to avoid poor performance, excess fatigue, and potential disaster.

1) Cardiac Drift.

 If you train and/or race with a heart rate monitor, you need to understand that heat, and humidity can alter your normal heart rate response to exercise. As the stresses of heat (and humidity) begin to take a toll on your body, your heart rate may increase disproportionately to your work load. Thus, at an intensity that would normally result in a heart rate of eighty percent of your maximum, your heart rate may begin to “drift” upwards, even though you are not racing or training any harder. This can negatively impact your psyche as well as your performance if you are not prepared for it.

2) Correct Hydration.

This one can be tough because it sounds so easy to do yet when it gets warmer, it is difficult to realize that fluid needs are increased. Add a little humidity (which decreases the effects of evaporative cooling), and the resultant higher sweat rate, and disaster can result.

Fluid needs become higher under the above conditions, but it is often difficult to consume more fluid due to the heat, the shunting of blood, and the body’s inability to process a significantly larger amount of fluid entering the stomach. When the body’s core becomes warmer, it shunts blood to the skin in order to dissipate the heat. This redirects blood from the gut which impairs your ability to digest and process the fluids you are drinking. If the environment is humid, it decreases the evaporative cooling mechanism which leads to a higher body core temperature which in turn leads to you not wanting to drink more to stay hydrated because you are either too hot to drink or because your stomach cannot process more fluids due to the reduced blood flow to the gut.

Dehydration – if fluid intake is not increased -is inevitable. A pre-acclimatization process can help, as can getting ahead, and staying ahead of your hydration requirements. You may actually have to force yourself to drink.

3) Electrolytes. With a higher sweat rate, often comes a higher electrolyte loss. If you are a very “salty” sweater, then there is not a sports drink on the market that will provide the necessary electrolytes you need to replenish what you are losing. You should use an electrolyte supplement (sodium, chloride, potassium, calcium, magnesium) with your higher electrolyte-containing sports drink.