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Heat Stress
by Master Amino Acid Pattern (MAP) Team Member Kelly Keane — Winner at Houston Marathon and Texas Man Triathlon
With the Hawaii Ironman quickly approaching, athletes need to be aware of the effects of heat on performance. It is important to be aware of the physiological adaptations to heat during exercise and what actions and precautions you can take to ensure a successful race experience.
What happens to the body in the heat?
In hot weather, body core temperature increases, skin temperature increases, and sweat increases. As a result heart rate and cardiac output increase. To maintain core temperature when it's hot, the human body shunts blood to the surface to cool it before it is returned to the heart to be pumped to the muscles. It also means that the heart must work harder during exercise, not only fuel muscles but also to help with cooling, so your heart rate rises. Athletes in the heat can sweat more than 1-2 L an hour and most athletes drink less than they sweat. The result is dehydration. Dehydrating only 2% of body weight can impair physical performance.
Tips for racing in the heat.
1. Acclimate
Heat acclimation can lead to an improvement in performance in hot conditions. Heat acclimation increases blood volume and sweat production. Basically, you will be better prepared for the heat and your body will be able to adapt better than if you did not acclimate to the heat before the event. Heat exposure during the acclimation process must be enough to raise the body core temperature and to produce sweat. In other words, just sitting out in the sun will not fully acclimate you for a hot race. Most adaptations occur within 7-14 days of exercise in a hot environment.
2. Consider and reconsider a hydration plan.
We know that heat acclimation will increase the need for fluid replacement because of a greater sweat response. To regulate body temperature, athletes must replace the water and electrolytes lost through sweat. Drink early and drink often. Keep a log of what you drink and when you drink in training. Remember what works. A sports drink is better than plain water because it has sugars to fuel muscles and brain, and electrolytes to hold fluid in the body and help replace sweat losses.
3. Keep your head cool
Pour cold water (make sure it is cold!!) over your head. This may help cool the body’s core temperature. Place some ice in your hat. Take those sponges!
4. Consider Salt
Increase your intake of salt when training and racing in hot conditions. Sprinkling a little extra on your food a few days before the race can help increase pre-race stores. Many athletes have had great success supplementing with salt. It is important to note however, that salt levels and sweat rates vary from athlete to athlete. Experiment in training not racing. Be sure to take in lots of water with supplemental sodium.
Racing in the heat is not easy, but by acclimating to the heat, staying hydrated, keeping our head cool, and including salt in your race plan, you may race faster than you think!! Good luck.
Other Articles from Kelly:
How to stay energized and hydrated during a marathon
Train for Aerobic Capacity and Lactate Threshold
High Altitude Training
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