As summer rolls in, I'm reminded how exercising bodies react differently in hot conditions. A hot summer sun can teach painful lessons, and I've certainly learned my share the hard way despite knowing better -- or thinking I know better.

Hot climates have no mercy when you aren't used to them -- One summer, while at a conference in Las Vegas, I hit the streets for morning workouts when temperatures teased toward the high 90s. Oh, I can handle this, I thought. Oh boy, was I wrong. In short order, I was scanning front yards for unguarded water faucets and even popped into a smoke-filled bar begging for water. Did I feel funny, in track shorts, dripping with sweat, at a bar lined with slot machines and gamblers who'd probably been there all night.

Here's the deal: It takes the body about 10 days to get used to heat, with most of the adaptation happening in the first three or four days. During that time, exercise less vigorously, using your heart rate as a guide. It will rise more quickly at a lower intensity, partly because your body hasn't learned yet it needs to sweat more, or sooner, to cool itself.

You might also notice that your sweat is really salty at first. As the body learns to sweat more, it also learns to conserve electrolytes (primarily salt, potassium and chloride) that keep the muscles and nerves primed and functioning well. Drinking water or a sports drink helps keep you sweating and hydrated too.

Don't be too cocky, though, because after five to six days without exercise in the heat you'll have to start over. Darn.