Builds strength from the feet up through the hips for better transfer of power.
Standing in the bottom of a squat position with feet hip-width apart and shoulders stacked over hips, shoot your legs out to the sides and your arms out to shoulder height (like a regular jumping jack) without moving your upper body. Do 16 to 24 reps.
More: How to Master the Squat
Single-Leg Mountain Climbers
Strengthens foot-strike muscles; engages hip flexors, quads, glutes, and core.
Starting in a plank position, with abs engaged, bend your left knee and pin it against the right knee. Hop your right foot forward to waist distance, landing lightly on the ball of your foot and keeping the left leg from touching the ground. Then, shoot the right foot back, keeping knees pinned and left leg raised. That's one rep. Do 16 reps; switch legs.
(Remember, what you do during your downtime matters just as much as your workout. Read A Perfect Day to learn the tips for ultimate fitness.)race.