Arms · Dumbbell
Dumbbell 21S
How to do the dumbbell 21s, the muscles it works, and the mistakes to avoid. Pulled straight from the Kovo app's exercise library.
- Equipment
- Dumbbell
- Difficulty
- Intermediate
- Logged as
- Weighted reps
- Movement
- Flexion
- Mechanic
- Isolation
How to do it
Hold a dumbbell in each hand with an underhand grip, arms hanging at full extension. Do 7 reps curling only to the halfway point, then 7 reps from halfway to the top, then 7 full reps from bottom to top. That 21-rep sequence is one set.
- 1Feel the biceps burn deepen across all three rep ranges
- 2Keep your elbows pinned at your sides the whole set
- 3Control each partial so the biceps stay under tension
Common mistakes
- Don't swing or use your back to cheat the weight up
- Avoid letting your elbows drift forward as you fatigue
- Don't cut the partial ranges short to make it easier
Muscles worked
The dumbbell 21s mainly works the biceps, with the forearms assisting.
- BicepsPrimary
- ForearmsSupport
- Front DeltsMinor
Kovo programs the dumbbell 21s for you and tracks it every session.
We build your whole program, drop the right lifts into each workout, and adjust your weights as you get stronger. Free on iOS and Android.
More biceps exercises
- How to do the resistance band bicep curl
- How to do the resistance band hammer curl
- How to do the barbell bicep curl
- How to do the cable bicep curl
- How to do the cable hammer curl
- How to do the overhead bicep curl
Last reviewed June 2026.