Medicine-Ball Russian Twist
Sit on the floor with your upper body and lower body elevated as you balance only on your glutes, holding a medicine ball in both hands directly in front of your chest with your elbows bent. Twist your body in an explosive manner to one side to touch the ball down to the floor, then quickly lift it up and bring it around to the other side to touch down again. Alternate at a controlled but brisk pace for reps — one “twist and touch” to each side equals one full rep.