“This program is about going as hard as you can for 20 minutes,” says Amy Dixon, a personal trainer whose newest DVD is Give Me 10! 10 Minute Workouts for a Total Body Tone Up (Stockyard, 2009). . “You elevate your heart rate for an intense, short period, so you’re quickly building muscular and cardiovascular strength.”

Warm up for 3 minutes by marching in place or walking on the treadmill. For the next 14 minutes, alternate between doing one of the following strength moves for 1 minute and jumping rope for 1 minute.

1. Squats. Keep your chest lifted. Hold weights to increase effort.

2. Push-ups on knees or toes. Keep your body in a straight line from your head to your knees or toes.

3. Bent-over row. Hold a weight in each hand. Stand with your knees slightly bent, and hinge forward at the hips so that your torso is at a 45-degree angle (keep your back straight). With palms facing each other, bend both elbows to 90 degrees while pinching shoulder blades together. Lower and repeat.

4. Sumo squats. Place your feet wider than your shoulders, and turn toes out 45 degrees. Keeping your chest up and shoulders back, squat straight down; then stand up and repeat. To increase intensity, hold hand weights on hips.

5. Overhead press. With your feet shoulder-width apart and a weight in each hand, bend your elbows so that weights are even with shoulders. Keep palms facing forward and wrists straight, and press weights overhead, as if you’re putting a box on a high shelf. Lower and repeat.

6. Bicycles. Lie on your back, hands behind head and feet off the floor, with knees bent 90 degrees. Raise shoulder blades 6 inches. Crunch abs, and rotate left shoulder toward right knee as left leg straightens. Alternate sides.

7. After your last jump-rope interval, walk in place or on a treadmill for 3 minutes to cool down.

Other 20-minute workouts:

>>Cardio blast. On a treadmill, elliptical machine, stationary bike, or outdoor path, warm up for 3 minutes. Then increase the intensity—either with resistance, speed, or incline—to a perceived exertion level of 6, on a scale of 1–10 (1 is easy; 10 is impossible). Stay there for 4 minutes. Recover for 1 minute. Do two more 4-minute intervals, one at a level 7, one at 8. Then cool down for 2 minutes.

>>Salute the sun. Find a quiet place and do 5–10 yogic sun salutations, which stretch and strengthen your muscles and calm your mind.