Lie on your back with arms and legs outstretched so your body forms an X. (A) Contract your abs and raise your head, arms, and legs a few inches off the floor. Keeping them extended, simultaneously bring your left arm and right leg together over your abdomen. (B) Lower your limbs back to start. Repeat to the opposite side. That’s one rep. Alternate for a full set. 10 to 12 reps
To make the move more challenging, keep your head, arms, and legs raised throughout the exercise. To make it a little easier, bring only your arm and leg off the floor each time.