4 Windshield Wiper
Sets: As many as needed Reps: 50
Grab a chinup bar with an overhand, shoulder-width grip and hang from it. Contract your abs and raise your legs up to your left side until they are in line with your left hand. Now rotate your hips so that your legs turn to the right side. If that's too difficult, perform the exercise with your knees bent. Perform 50 total reps, doing as many sets as you need to (and resting as needed in between) until you hit that number.