Gretchen Reynolds’ New York Times bestseller is an innovative guide to getting fit using cutting-edge science.Discover the amazing restorative powers of chocolate milk on tired muscles, the pros and cons of barefoot running (and why running can actually be good for your knees) plus the effect music can have on a workout.Reynolds shows how fidgeting burns 300 calories per day, why it’s a bad idea to stretch before a run, and how even just 20 minutes of regular exercise can transform your health. And that lucky underpants really do work.