Sit on the edge of a chair or bench with your hands next to your thighs. Lift your body out just in front of the chair, with your feet flat on the floor and your knees bent. Lower yourself down so your elbows bend no more than 90 degrees and push yourself back up.
Start off with a few small sets and build up from there.
Straightening your legs increases the workout.
Avoid this exercise if you have wrist or shoulder problems.