This exercise provided courtesy of Billy Polson, founder and co-owner of DIAKADI Body training gym, voted best personal training gym in San Francisco by CitySearch in 2006.
Hammer curls are tough to begin with, but doing them while balancing in a modified squat against a stability ball engages your whole body in a battle for stability, and, ironically, forces you to do the actual lifting of the dumbbells with your isolated biceps and brachialis muscles.
Holding a dumbbell in each hand with your palms facing inward, lie back against a stability ball so that your body is supported from the upper buttocks to the lower back and your upper back is not touching the stability ball. Bend your knees into a modified squat with your hips bent, your knees at a 90-degree angle, and your feet planted about hip-width apart approximately two to three feet in front of the stability ball (see Photo 1).
- From the starting position, lift the dumbbells up and do a full hammer bicep curl, contracting your biceps up as far as you can. Keep your shoulders steady throughout the curl (see Photos 2 and 3).
- From the top of the curl, reverse the motion and return to the starting position. Be sure to fully extend your arms to get a good stretch at the bottom of the curl (see Photos 4 and 5). Complete 10 reps for a full set.