Physical therapist Robert Forster, who works with many Olympic athletes, swears by this abs exercise. "It looks simple but it's quite taxing, and most importantly, it's safe for everyone! It works for my student athletes as young as nine or 10 years old, my elderly patients with osteoporosis, as well as my Olympic gold medalists," he says.
Grab and pair of dumbbells (start lighter and gradually increase your weight when you feel ready) and lie faceup with your knees bent at 90 degrees, feet touching the floor. Brace your abs in tight to your back as you lift your right leg up (still bent at 90 degrees) above your hip and reach your left arm overhead, palm facing in (your right arm is extended down by your side, just above the floor, palm facing in). Quickly switch your arms and legs, raising your right arm overhead and lowering your left down by your side, and lowering your right foot to the floor and lifting your left leg. That's one rep. Exhale every time you switch sides, keeping your abs braced in tight the entire time. Do 2 sets of 10 reps.