Jonathan Pozniak

What it does: Strengthens the abs and fronts of thighs; improves balance.

How to do it: Sit on a step stool, hands behind you. Place both heels on the floor, feet and knees together, knees almost straight. Lean back and, balancing on your buttocks, bend both knees up toward you by pulling with your abs. Lower your legs, but don’t let them touch the floor.