You've probably seen medicine balls at your gym. These colorful weighted balls — ranging from 2 to 25 pounds — can actually do more for your physique than dumbbells, weight machines and many other fitness tools. Because they're spherical, they make standard exercises more challenging. They can also be caught and thrown with a partner or against a wall. And because you can use the medicine ball while running, lunging, jumping and catching, it serves as a great tool for sport-specific training. Try this total-body workout, which uses nothing but a weighted medicine ball to challenge you with new movements, and sculpt a knockout bod in record time.

Medicine Ball Lunges with Oblique Twists

Muscles worked: glutes, quadriceps, hamstrings, calves, obliques, Sets/reps: 2 sets of 8 to 15 reps

Stand tall with your feet hip-width apart, holding a medicine ball against your torso, just below your chest. Lift your right foot and take one long step. As your foot lands, bend both knees until your right thigh is parallel to the floor and your left is perpendicular to it (your left heel will come up off the floor). While you're executing the lunge, twist your torso to the right. Go far enough that you feel some work happening at the waist. Pause for a second and, pressing off the ball of your right foot, unwind from the twist and step back to your starting position. Repeat all reps on the right side, and then switch to the left to complete one set. Note: As you lunge, do not let the knee of your lead leg extend past your toes. If it does, lengthen your stride so that your knee remains in line with your ankle.