However, there's more to this issue than just sweat. We need to understand what is happening when we sweat, so we are better able to reduce the risks of overheating.

Many think that it is the evaporation of sweat that cools the body. But that is not true. The evaporation does provide a small amount of cooling, but it is the sweat itself -- the expulsion by the body of superheated water, that cools. Just like an automobile engine, the water absorbs the heat and transfers it out, leaving the body cooler.

This is important to understand, because when you sweat heavily, the accumulation of moisture on the skin impedes the expulsion of more superheated water. The result is that you run hotter than you need to. What's the answer? Keep toweling off the sweat so that more can be exhausted, and keep the water coming in to avoid dehydration. Because if you are losing water you need to replace it.

One coach I know has the following rule. On a hot day, a player leaving the field gets a towel and a cup of water. Another insists that his players have two jerseys, one for the first half and the fresh dry one for the second half.

Whatever system you use, remember to keep your players toweled down and hydrated. They will be stronger and last longer because of it. It is the core temperature, not the surface temperature that you are trying to control. The more water they can loose, the cooler they will be.