What’s Hiding in Your Running Clothes?

That sweaty heap of running clothes in your hamper sure is smelly, but the stink may not be the worst of it. The germs taking up residence in your unwashed clothing can actually make you sick—and they aren't so easy to get rid of, either.

To get to the bottom of this, shall we say, "funky" situation, we chatted with a physician, a microbiologist, and a hygiene expert. What we learned was equal parts disturbing and educational.

Microscopic organisms love the hot and sweaty parts of your body.

Microbes need water, food and a warm environment to grow, says Jason Tetro, a microbiologist and author of "The Germ Files."

"When we exercise, we are providing all three to these tiny organisms, allowing them to grow," he says. "On some areas of the body, like the arms and abs, there are only a few hundred per square centimeter. But in places like the underarms and toes, that number could be in the millions for the same area."

High numbers of tiny organisms produce a lot of byproduct. In other words, that repugnant odor you emit after a run is actually bacteria waste. Charming, isn't it?