This fast-paced workout will elevate your heart rate while strengthening your core. Do each exercise for 50 seconds. Then rest and transition to the next exercise in 10 seconds. Consider doing 2 to 3 circuits for a longer, more challenging workout.

Bicycle

Lie on your back. Lift your feet off the floor and pull your knees toward your chest. Place your hands behind your head, with your fingertips touching behind your ears. Rotate your right shoulder toward your left knee as you extend your right leg out, parallel to the floor. Rotate your torso and move your left shoulder toward your right knee as you extend the left leg out. Repeat, alternating shoulder to knee.

Combo Crunches

Lie on your back. Place your hands behind your head, with your fingertips touching behind your ears. Lift your knees in the air so your thighs and torso form a 90-degree angle. Crunch your upper body up, lifting your shoulders off the ground as you bring your knees toward your chest. Lower the upper body, return to a 90-degree angle, and repeat.

Plank

Assume a standard push-up position on your toes, with your hands placed directly under your shoulders on the floor. Now, lower your elbows to the ground. Hold the position with your body straight from your shoulders to your heels. Try lifting one foot off the floor to make the move more difficult.

Knee Tucks

From the push-up position, pull your right knee into your chest as you contract your abs. Hold for one count and return your leg to the starting position. Repeat on the other side. To increase the difficulty, pick up the pace and move quickly, tucking one knee and then the other.

Toe Touches

Lie on your back with your arms and legs extended. Slowly raise your right arm as you raise your left leg. Contract your abs as you touch your left toes with your right hand. Lower to the starting position and repeat on the other side.

Crisscross

Lie on your back and place your hands under your buttocks to help support your lower back. Raise both legs about six inches off the floor. Slowly cross your right foot over your left and then switch, crossing your left foot over your right. Continue crisscrossing the feet as you contract your lower abs. To make this exercise easier, raise your legs higher to reduce the stress on your abs and lower back.

Bird Dogs

Position yourself on your hands and knees on the floor. Raise your right arm in front of you, parallel with the floor. At the same time, extend your left leg out behind you, parallel to the floor. Lower to the starting position and repeat with your left arm and right leg.

Knee to Elbow

Stand with your arms raised overhead. Raise your left knee towards your chest as you bring your right elbow down to meet it, rotating your torso. Return to the starting position and repeat with the right knee and left elbow. To increase the intensity, speed up the movement and add a hop as you raise your knee.

Standing Side Crunches

Stand with your feet wider than your hips and lower into a plié squat position. Place your left fingertips behind your left ear. Extend your right arm down your right side. Lean to the right and reach your hand towards your right ankle. Return to start. Crunch on the right side for 25 seconds, then switch to the left.

Walk Out Plank

Stand with your feet hip-width apart. Bend at the waist and place your hands on the floor. Keep your feet where they are and walk your hands out in front of you until your body is extended in a plank. Use your hands to walk yourself back to the starting position. Do your best to keep your legs straight as you walk your hands out to plank and back.

Lori Rice, M.S., is a nutritional scientist and author with a passion for healthy cooking, exercise physiology, and food photography.