With each stride, up to five times your weight slams through your feet, ankles, knees, hips, and spine. If your muscles are weak, you risk injury, says Bill Hartman, P.T., of Indianapolis Fitness and Sports Training. Do these drills 3 days a week to strengthen your weakest areas. (Speaking of weak, check out the hardest workout you're not doing for a total body interval sweat session.)

Ankle Mobilizer

Ankle flexibility: From a staggered stance, palms on a wall, bend your knees and shift forward until you feel your forward ankle stretch. (Try not to raise your heels.) Bring your front knee close to the wall. Hold for 3 seconds. That's one rep. Do 20 reps, switch legs, and repeat.

Reverse Lunge And Rotation Hip mobility: Step back with your left foot and lower your body into a lunge as you rotate your upper body to the right. Return to the starting position. That's one rep. Do three sets of 12 and then repeat, this time stepping back with your right leg while rotating to the left.

Single-Leg Straight-Leg Deadlift

Hip stability: Hold a dumbbell in your left hand. Lift your right foot as you slowly bend and lower the dumbbell. Once it reaches mid-shin, return to upright. Complete 12 reps on one leg, and then switch sides and repeat. Do three sets.

Wall-Press Abs

Core strength: Lie down. Now brace your core and push against a wall as you lower your bent right leg and touch your heel to the floor. Reverse the move and repeat with your left leg. Keep alternating for 60 seconds, and then rest for one minute. Do two or three sets. Are you tired yet? Don't worry, find out how to be a better athlete without moving a muscle.