Crunch with a twist
Works shoulders, obliques and lower abdominals
(A) Sit on the ball and walk your feet forward, rolling the ball
so that it’s beneath your middle back. Keeping your feet flat
on the ground, hold a light dumbbell (3 pounds for beginner, 5 pounds for more advanced) vertically with your arms straight out in front of you about 45 degrees above your hips.
(B) With abs contracted, crunch up, twisting your torso to your left, then to your right, before lowering back down to starting position. Do one set of 8 to 12 reps, working up to two to three sets of 8 to 12 reps.