Sit on a coffee table or low chair and place your hands directly outside your hips, fingers facing forward. Walk your feet a couple of steps away, slide your glutes off the table and lower your body so that your arms form 90-degree angles. Press up and contract your triceps at the top, then repeat, keeping your low back and hips close to the table. The closer your feet are to your body, the easier the exercise is.
Overhead dumbbell extension
Sit on a chair or coffee table, then grasp a dumbbell with both hands and raise it over your head. With your upper arms stationary, lower the dumbbell behind your head by bending your elbows, then straighten until both arms are again extended overhead. Contract at the top, then lower and repeat. Keep your elbows tight and close to your head throughout.