|The Greeks were on to something 2,500 years ago when they tossed around a prop akin to the medicine ball, that sand-filled leather or vinyl orb that remains a key piece of equipment at boxing gyms. "The medicine ball lets you work muscles from all angles, so you can isolate particular muscle groups even better than with free weights or a machine," says Donald Chu, president of the National Strength and Conditioning Association and author of Plyometric Exercises with the Medicine Ball.
Medicine balls range wildly in size and weight, but for starters, moderately fit women might try a six-pounder; men, an eight-pounder. You can use it for partner exercises, but to work it solo, try the giant circle, which taxes both the lower and upper body. Stand with your feet shoulder-width apart, knees slightly bent, and hold the ball directly overhead. With your arms straight, slowly sweep it to the right in a full circle, keeping it close to your body. As the ball comes down, bend into a semi-squat, and straighten as you reach 12 o'clock. Do ten in each direction.