Begin by lying on your back with your knees bent and your feet flat on the ground, about two feet from your butt. Hold five- to eight-pound dumbbells in both hands at your chest with your elbows on the floor.
Keeping your hands at your chest, roll up to a sitting position. Twist your ribs to the left as you "punch" your right hand to the outside of the left knee.
Bring the right hand back to your chest as you untwist, bringing your torso back to the centre, and roll down to the ground.
Repeat the sit-up, twisting to the right side to complete one rep.