Weighted Squat and Twist on a Bosu Ball / Terra-Core
Stand with your feet wider than shoulder-width apart with your toes pointed slightly out. Hold a dumbbell at chin or chest level. (I used a 15-pound weight here.) This is your starting position.
Keeping your back flat and core engaged, push your hips backward, bend your knees, and lower your body until your thighs are parallel to the ground.
At the bottom of your squat, twist your torso to one side. Try to keep your knees facing forward.
Twist back to center, and with your weight focused on your heels, push yourself up to the starting position to complete one rep. Alternate your twist to the other side on your next rep.