Sit with your back to a step platform or the seat of a chair, and wrap your hands around its front edge. Spread your fingers so your little fingers are pointing to the platform's outside edge (doing so will help keep your elbows pointing straight back instead of bending to the side). Extend your legs out a foot or two and keep only your heels on floor. Lean back at a slight angle so your body weight is shifted to the back of the arms (this targets the triceps), then lower and raise your body. Perform two sets of 12 to 15 reps.