Begin lying on your back with your legs in the air, toes toward the ceiling, holding one or two dumbbells over your chest with straight arms. Engage your abs to press your lower back into the mat while lifting your head, neck, and upper back off the mat.
Exhale and round your lower back so the bottom of the pelvis raises as you lift your upper body an inch higher off the mat. Aim the medicine ball toward your ankles as you perform this double crunch.
Inhale, and lower your pelvis and upper back an inch toward the floor.