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 ...

Beth Skwarecki is Lifehacker’s Senior Health Editor, and holds certifications as a personal trainer and weightlifting coach. She has been writing about health for over 10 years. The more you work out, ...

A.V. Hill was a 4:45 miler and already had a Nobel Prize for work in muscle physiology when he and Lupton began studying VO2 max. The experiments involved subjects running around Hill’s back garden in ...