Weighted Crunch

Hardens your rectus abdominis and obliques (belly muscles and side torso muscles), so you can absorb impacts during contact sports such as martial arts, boxing, football (and letting your 5-year-old nephew hit you in the stomach to show him what a bad-ass you are).

Lie on your back with your knees bent and your feet flat on the floor.

(A) Hold the ball between your palms, resting it on your forehead. Keep your elbows out to your sides.

(B) Slowly raise your head and shoulders off the floor, hold the position for 5 seconds, then lower yourself. Do three repetitions.

(C) Now perform the crunch again, but rotate your head and shoulders slightly as you rise, alternating left and right for six repetitions. Repeat the entire set of nine repetitions — center, left, and right — three times.