Think outside the dumbbell rack for a fresh way to up the ante on your workout: Grab a medicine ball, says Kaisa Keranen, an exercise physiologist and the owner of KaisaFit, a pop-up HIIT fitness class in Seattle (plus the creator of our 30-day tabata challenge). "It's an incredibly functional and versatile piece of gym equipment," Keranen says. Because of the ball's spherical shape, you can easily go with the flow of a fast AMRAP set (HIIT-speak for "as many reps or rounds as possible"). Grip it anywhere—the weight is distributed evenly—and you can use it more dynamically and through a larger range of motion than other weights. (You would never toss up a dumbbell and catch it, after all.) That means you're able to target more muscles from more angles, Keranen says.
In fact, a recent study in the Journal of Strength & Conditioning Research showed baseball players who added medicine ball moves to their training improved their strength, power, and athletic performance more than those who stuck with body-weight exercises. Medicine balls are in most gyms and weigh anywhere from two to 30 pounds. When choosing the right one for your routine, "this isn't where you want to max out on weight," Keranen says. "Pick a ball that slows down the normal action of whatever moves you'll be doing but that still allows you to keep good form for eight to 12 reps." That way, you're challenging muscles enough to firm them but still moving quickly and long enough to make sure you melt off lots of calories.
How it works: Start with 3 sets of the warm-up: 10 each of squats, lateral lunges, and plank-to-downward-dogs, plus 30 seconds of high knees. Do the moves in part A for 30 seconds each, resting for 15 seconds in between exercises. That's 1 set. Do 3 sets, resting for 15 seconds between sets. Repeat that structure for part B.
Total Time: up to 30 minutes
1. Part A - Squat Jump to Press
Stand with feet hip-width apart, holding medicine ball at shoulder height with arms bent down. Squat to start. Jump to stand with feet together as you press ball overhead. Immediately jump to start position. Repeat quickly for 30 seconds.
2. Part A - Mountain Climber
Start on floor in plank with both palms on ball and feet hip-width apart. Pull right knee up to touch right elbow, then back to start. Switch sides; repeat. Continue alternating sides for 30 seconds.
3. Part A - Around the World
Place ball on floor and stand with feet hip-width apart about 6 inches behind it, arms by sides. Tap left toes to top of ball, then quickly switch feet as you rotate slightly clockwise. Continue quickly alternating foot taps as you circle around the ball. Switch directions and repeat. Continue quickly alternating directions for 30 seconds.
4. Part A - V-Sit Twist
Sit on floor, holding ball at chest with arms bent out to sides. Shift weight onto tailbone and lift straight legs up 45 degrees to start. Rotate torso toward left, then back to center as you lift ball overhead. Lower ball to chest, then rotate torso toward right, sweeping ball diagonally overhead as you return to center. Continue alternating sides for 30 seconds.
5. Part B - Squat Arc
Stand with feet hip-width apart, holding ball with both hands, arms extended down. Squat and lower ball to touch floor to start. Quickly stand, pivoting on left foot and raising ball overhead and to the right. Return to start. Switch sides; repeat. Continue quickly alternating sides for 30 seconds.
6. Part B - Slider Push-Up
Start on floor in plank with right hand on ball and left hand on floor (if you need to modify, drop to knees). Do a push-up. Roll ball to left hand, then do a push-up. Continue quickly alternating sides for 30 seconds.
7. Part B - Rotating Lunge Switch
Stand with feet hip-width apart and hold ball in both hands at chest with arms bent out to sides to start. Step right foot forward into a lunge, bending legs 90 degrees, then rotate torso toward right. Return to start. Switch sides; repeat. Continue quickly alternating sides for 30 seconds.
8. Part B - V-Up
Lie face up on floor, holding ball with both hands overhead and resting on floor. Lift arms, head, shoulders and legs off floor to start. Rise up onto tailbone (so body forms a V) and pull ball into chest. Slowly lower to start. Repeat (without lowering to floor) for 30 seconds