9 killer core moves from sports medicine physician Dr. Jordan Metzl

Dr. Jordan Metzl, a sports medicine physician at the Hospital for Special Surgery in New York City, released his newest book "Dr. Jordan Metzl's Workout Prescription" on Tuesday -- and it's full of workouts for athletes who are short on time. Below, we've excerpted one of his core workouts that can be done anywhere, anytime.

If there's one thing I like about the term core, it's the nuclear connotation: that of a central power source where a reaction begins. Your core muscles (not just your "abs," but every fiber in your torso) help generate just about any movement, especially athletic ones. A strong core is a fundamental part of a healthy kinetic chain and prevents common injuries like lower-back pain. Plus, I've noticed a phenomenon in myself and in many of the folks I treat: Strong core = Feeling great.

First 10 minutes

3 minutes: Do a dynamic warmup (my favorite involves 30 seconds each of jumping jacks, hops and other exercises).
1 minute: Rest.
6 minutes: Perform each exercise below for 1 minute, cycling through the set two times.

Single-leg, single-arm plank

Assume a pushup position but with your weight on your forearms. Brace your abs, clench your glutes, and keep your body straight from head to heels. Raise your left leg and extend your right arm out in front of you. Hold for 5 seconds, then lower your arm and leg and raise your right leg/left arm for 5 seconds. Alternate for the allotted time.

Bicycle crunch

Lie faceup with your hips and knees bent 90 degrees so that your lower legs are parallel to the floor. Clasp your hands behind your head. Lift your shoulders off the floor and hold them there. Twist your upper body to the right as you pull your right knee in as fast as you can until it touches your left elbow. Simultaneously straighten your left leg. Return to the starting position and repeat to the other side.

Prone cobra

Lie facedown on the floor with your legs straight and your arms at your sides, palms down. Contract your glutes and lift your head, chest, arms, and legs off the floor. Simultaneously rotate your arms so your thumbs point toward the ceiling. Your hips should be the only part of your body touching the floor. Hold for a 5 count, then return to the starting position. Perform as many reps as you can in the allotted time.

Second 10 minutes

1 minute: Rest.
9 minutes: Perform each exercise for 1 minute, cycling through the set three times.

Three-point core touch

Assume a push-up position. Quickly move your right leg forward so your right heel lands outside your right hand. Pause and return to the pushup position. Now quickly move your right leg forward so your right foot lands outside your left hand, and then return to the push-up position. That's 1 rep. Work for half the allotted time, then repeat with your left leg.

Single-leg hip raise

Lie on your back with your left knee bent and your left foot flat on the floor. Raise your right leg so it's in line with your left thigh. Push your hips up, keeping your right leg elevated. Pause, then slowly return to the starting position. Switch legs halfway through the allotted time.

Crab roll

Sit, knees bent, with your palms and feet on the floor. Raise your hips so your body is in a straight line from your knees to your shoulders; this is the starting position. Lift your right foot and left hand and flip over to your right, placing your left hand back on the floor and kicking your right leg out behind you. (Keep it elevated.) Flip back to the starting position. That's 1 rep.

Third 10 minutes

1 minute: Rest.
9 minutes: Perform each exercise for 1 minute, cycling through the set three times.

Leg tuck and twist

Sit on the floor, leaning back 45 degrees, your legs straight and palms on the floor behind you. Lift your legs off the floor. Pull your knees toward your left shoulder as you twist your torso to your left. Return to the starting position and repeat to your right.

Single-leg side plank

Lie on your side and use your forearm to support your body. Raise your hips until your body forms a straight line from shoulders to ankles. Then raise your top leg as high as you can, holding it there for the duration of the exercise. Halfway through the prescribed time, switch sides.

Figure 8

Lie on your back with your arms at your sides, palms down. Raise your legs so they form a 45-degree angle with the floor. Now make big, looping circles with your legs, first to your left and then to your right, forming a sideways figure 8. That's 1 rep.