For this drill, think back to your old P.E. classes. Butt-kicks are a classic drill that help improve mobility as your quads flex and extend almost to their maximum range of motion. Besides mobility, the motion is part of an active warm up that gets your muscles ready to work hard before a run or race. Pay attention to two things as you go through this drill:
1. USE YOUR FEET
Instead of landing on your toes or the ball of your foot, land full-footed. This provides a stable platform rather than the smaller surface area on the ball of your foot, keeping the stress off your achilles.