I like to challenge myself physically, whether it's working out, cycling or cross-country skiing. I've heard about VO2 max ...

If you're a fitness fiend or working to improve your health, you're probably always looking for ways to run faster and farther, train harder and push your limits. You might even already track a number ...

For decades, elite runners have traveled the world to train at high altitude. When oxygen levels in the air are low, the body responds by producing more red blood cells—the cells responsible for ...