Many runners hold tension in their upper body, which can make your regular run feel twice as hard. Try this simple trick to check yourself: Roll up a sheet of paper and run with it for a few minutes (as if you were holding a baton in a 400-meter relay). If the paper comes back crunched, you are squeezing too hard! Allowing your hands to loosen up translates into reduced tension in the shoulders and less wasted energy.

—Andrew Chaddick, MS, CSCS, a personal trainer at The Houstonian Club in Houston, Texas