How to do the Dumbbell 21's
Primary: Biceps · also works Forearms.
Dumbbell 21's, also known as 21s or Barbell 21s, is an effective bicep exercise that targets the bicep muscle through a combination of partial and full repetitions. This exercise is great for developing the overall size and shape of the biceps. By performing 21 reps in total – seven lower-half reps, seven upper-half reps, and seven full-range reps – you ensure comprehensive muscle engagement and growth.
Step by step
- 1
Stand up straight with a dumbbell in each hand, palms facing forward.
- 2
Perform 7 reps of bicep curls from the bottom of the movement to the halfway point (90 degrees).
- 3
Next, perform 7 reps from the halfway point (90 degrees) to the top of the movement.
- 4
Finally, perform 7 full-range reps from the bottom to the top of the movement.
Coaching cues
- Maintain a controlled tempo throughout the exercise to maximize muscle engagement.
- Keep your elbows stationary and close to your body to focus the effort on your biceps.
- Avoid using momentum to lift the weights; focus on a slow and deliberate motion.
Sets, reps and where it fits
Muscle
3–4 × 21–21
rest 60–90 s
Strength
not a strength lift
use for assistance
Fat loss
3 × 21–21
rest 45–60 s
Dumbbell 21's alternatives
Same movement pattern, different equipment or difficulty. Swap one-for-one in any plan.
Frequently asked questions
What muscles does the Dumbbell 21's work?
Primary: Biceps. Secondary: Biceps, Forearms
How many sets and reps of Dumbbell 21's should I do?
For muscle: 3–4 sets of 21–21 reps. For strength on compound lifts: 4–5 sets of 4–6. Rest 60–120 seconds between sets.
What can I do instead of the Dumbbell 21's?
Same movement pattern, different equipment: Concentration Curl, Dumbbell Curl, Hammer Curl, Reverse Curl, Incline Dumbbell Curl, Zottman Curl.
Is the Dumbbell 21's good for beginners?
With some training experience, yes. Beginners should start with one of the easier alternatives listed and progress to it.