Alternate arm and leg raises strengthen your back muscles and to help with your posture.
Lie on your front with your legs straight and your arms stretched out above you.
Rest your head to one side or rest your chin on a pillow.
Gently tighten your stomach muscles, then raise one leg up straight off the floor.
Your leg will only lift a few inches.
Lower this leg and repeat with the other leg.
Next, raise the leg up off the floor whilst simultaneously lifting the opposite arm just a little.
Hold this position, and control the movement as you lower it back down then and repeat with the other opposite arm and leg.