.How running Affects Your Body

How Running Affects Your Body

Weird Science

Running makes you lean and strong. It also gives you twitchy legs, black toenails, and an urgent need to find a bathroom now. Why? Here, doctors, therapists, and physiologists offer explanations and practical solutions for our most perplexing body issues.

Runners know bodies. We understand what training does for our legs, lungs, and heart. We're also intimately familiar with the other, less attractive ways running impacts our bodies. But we don't necessarily know why we have to pee even though the shrubs got watered just two miles ago. Or why our knees crackle and pop as we go down stairs. Or why someone way heavier can kick our skinny butts in a half-marathon. So Runner's World consulted doctors, physiologists, nutritionists, and other experts, and frankly asked them the most quirky and perplexing questions about the bodies we know and love. We also asked for practical advice about how to deal with our issues. Here's what the experts said.


1 How can someone just as short/tall/skinny/fat as me run so much faster?
Plenty of reasons why your doppelganger leaves you in the dust. Speedwork may be his religion, and you haven't converted yet. This may be her 50th 10-K, when you're just stepping up to the distance. He may have a new girlfriend standing on the sidelines; she may have a postpregnancy goal she's gunning for. "Just because two people are long and lean or have a powerful build doesn't mean they match up in terms of VO2 max, mental toughness, or injury history," says Kristen Dieffenbach, Ph.D., assistant professor of athletic coaching education at West Virginia University. Many performance components, such as endurance, pace, turnover, and mental toughness, can be improved with planned, systematic training, except for one very significant one: genetics. "Muscle-fiber type and VO2 max are genetic
That's how some people who don't even train can blow by you on race day."
Running Rx You can't change your genetic destiny, but you can greatly influence your performance by training smart, adding speedwork, tempo runs, running-specific drills, and strength training to your routine. Plus, remember there's a reason it's called a PR: It's a personal record. Beat it—not yourself—up.


2 Why does my GI tract act up when I'm running?
Some people get headaches when they're stressed. Runners get the trots. A 2008 study on 1,281 Dutch runners found that at least 45 percent complained of some gastro-related issue during the run. "The GI tract is very sensitive to stress, and running—or the anticipation before a race—is definitely stressful," says Darrin Bright, M.D., family physician and sports medicine specialist in Columbus, Ohio.

When you run, your intestines take a double hit: The motion jostles their contents and speeds things along. Plus, blood, essential for your tract to stay on track, is rerouted to vital organs and muscles in your lower half, disrupting the sensitive balance your body has for fluid absorption and possibly causing dehydration, which can lead to cramps that force you to beeline for the bathroom.
Running Rx Dr. Bright recommends putting the ix-nay on bathroom-inducing high-fiber and high-fat foods 24 hours before a race or long run, and fueling up on benign, already-tested, plain meals.