running.competitor.com
By Tawnee Prazak | July 24, 2014
What is heat acclimatization, and why is it important?
In my last article, we discussed the physiological detriments to exercise in heat. Fortunately, the human body can adapt to the stress of heat with repeated exposure, resulting in less strain and increased comfort. So whether you’re training for a hot race or live in a hot climate, here’s what you need to know about heat acclimatization for optimal performance.
What Happens With Acclimatization?
You Become A Better Sweater
After acclimatizing to exercise in the heat we begin to sweat earlier, we sweat more and at a faster rate, our sweat glands fatigue less and the body better distributes sweat. There’s also less sodium content in the sweat, which helps with water retention and maintaining fluid levels to prevent dehydration. The result of better sweating is better cooling, meaning skin and core temperatures stay within reason and early fatigue, hyperthermia and heat illness are less likely. Fluid intake is essential to maintain these functions (see “Role of hydration†below).
Cardiovascular Function Improves
Benefits include a decrease in heart rate, increase in plasma volume and improved blood flow. With more plasma, there’s more blood available to go to the skin’s surface for heat dissipation and to the working muscles. Most important, adaptations put less stress on the heart, resulting in a decrease in heart rate at any given intensity and increase in stroke volume (amount of blood pumped out of the heart chamber).
Exercise Performance Increases
The non-acclimatized person will run slower and fatigue faster in heat; but, as acclimatization takes place, these negative effects will fade and running capacity and performance will increase due to improved thermal comfort and lower perceived exertion.
How to Acclimatize
Each runner is slightly different, but generally it takes about two weeks of continual training in the heat to acclimatize. Averaging at least one hour of moderate exercise daily in hot conditions is enough to get results in that timeframe. Gradually ease into heat training by keeping a low intensity at first (quality runs can be done in a cool gym). Depending on your normal running volume, fitness level, and natural heat tolerance, you may need to reduce your running volume slightly or significantly in the first days of heat exposure. As adaptations occur, intensity and volume can increase.
Certain adaptations occur quicker than others. Decreased heart rate can occur in as little as five days, while changes in sweating response could take weeks. Furthermore, trained endurance athletes usually adapt faster than untrained individuals.
More:
http://running.competitor.com/2014/07/training/heat-acclimatization-for-runners_12035
