If you don't have an exercise ball handy, swap this move for a simple elbow plank: instead of doing the number of reps below, hold for 30 seconds.
- Begin in an elbow plank.
- Contract your abdominals to keep yourself up and prevent your booty from sticking up. Keep your back flat and your neck and spine in neutral position. Picture your body as a long straight board, or plank.
- Use your elbows to pull your body forward, then come back to your starting position. This completes one rep.
- Do 12 reps, rest for 30-60 seconds, and complete two more sets.