This exercise provided courtesy of Mike Clausen, founder and co-owner of DIAKADI Body training gym, voted best personal training gym in San Francisco by CitySearch in 2006.
Dumbbell 21 curls use three ranges of curling motion—lower half only, upper half only and full range of motion—to make your biceps beg for mercy. Select a weight a little less than the normal weight you would use when doing curls for 12 reps. Switch the order of top half and lower half lift from workout to workout to mix it up and keep your muscles guessing.
Stand upright with dumbbells held in each hand at your sides and your palms facing forward. Keep your upper arms at your side throughout the exercise. Hold your elbows in front of your ribs; this will help keep the biceps muscle engaged throughout the movement, and will prevent you from inadvertently swinging your body to lift the weight (see Photo 1).
- From the starting position, use a scooping motion to begin as you lift the dumbbells up together until you are halfway through a full bicep curl, pause, then lower your arms back to starting position. Flex your bicep at the top of the movement, and resist the weight all the way down. Don't fully unlock your elbow at bottom of movement. Try your best to never allow your bicep to rest at top or bottom of any of the three series of movements. Do a total of seven of these lower-half bicep curls (see Photo 2).
- After you have finished seven of the lower-half bicep curls, you are ready to move on to upper-half biceps curls. Lift the dumbbells up to a starting point that is halfway through a full range bicep curl, with your elbows at a 90-degree angle and the dumbbells held out in front of you. Curl the dumbbells up together to the top of a bicep curl, but lower down only until your elbows are back at the 90-degree angle. Again, flex your bicep at the top of the movement, and resist the weight all the way down. Do a total of seven of these upper-half biceps curls (see Photos 3 and 4).
- After you have finished seven of the upper-half bicep curls, lower the weights to the original starting position, with the dumbbells held in each hand at your sides and your palms facing inward. Lift the dumbbells up together and do seven full range of motion biceps curls. When you have finished seven of these curls, you have completed one set of hammer 21 curls (see Photos 5 and 6).