HOW TO DO IT Lay a kettlebell flat side down with its handle facing away from you. Place both palms on the round part, and assume a pushup position. Slowly bring one knee as close to your chest as you can. Touch the floor with your toes, and quickly return to pushup position while maintaining good form. Repeat with the other knee. Alternate legs for 30 seconds.
BENEFIT The instability of the kettlebell forces your abs, lower back, and hips to work harder than they do in a traditional mountain climber.
2. Resistance band
EXERCISE Anti-rotation band speed fly
HOW TO DO IT Anchor one end of a resistance band at hip level. Grip the handle with your right hand and cover that hand with your left. Kneel on your right knee (with the anchor point on your right) and press the handle in front of your chest. With your elbow slightly bent, let your right arm open toward the anchor point, and return explosively to the starting position. Do 10 to 12 reps on each side.
BENEFIT You're not only strengthening your pecs but also carving your abs as they fight to prevent your torso from rotating.
EXERCISE Overhead barbell walk
HOW TO DO IT Grab the bar using an overhand grip that's about twice shoulder width, and raise it directly overhead. (Add weight only when you can maintain proper form.) Keep your arms straight, your body tense, and your head back. Walk forward for 5 to 10 seconds, pause, and then walk backward for 5 to 10 seconds. That's 1 rep. Do 2 sets of 2 reps, resting 60 seconds between sets.
BENEFIT Balancing the bar targets your shoulders as well as your torso's stabilizing muscles, including hips, obliques, and lower back.
4. Medicine ball
EXERCISE Windmill slam
HOW TO DO IT Hold a medicine ball at waist height and assume a staggered stance, your left foot 2 to 3 feet in front of your right, knees slightly bent. In one smooth "windmill" movement, swing the ball counterclockwise, arc it above your head, and slam it to the floor outside your left leg. Then catch the bounce. Do this 10 times, switch legs, and repeat.
BENEFIT You'll send your calorie furnace into overdrive while chiseling your rectus abdominis—better known as your six-pack.