FastFit BETA
IntermediateStrength
Drag to rotate 360°
Speed for this exercise

Dumbbell 21s

Biceps Tier B for Biceps Dumbbell Isolation Pull
Try it now
3sets
21reps
90srest
~4.9kcal/min

How to do it

Muscles worked

Secondary
Forearms

Secondary muscles help but are not the main target

See the full tier list · Biceps

Feel it right

Where you should feel it, the one cue to remember, and quick fixes when you feel it somewhere else.

You should feel it inFront of arms

Front of the upper arm pumping up.

Key cue (the coach says it during the set)“Elbows pinned, curl up, squeeze, lower slowly.”

Tempo · Up 1 s · squeeze 1 · down 3 s

Choosing the load: Pick a weight you finish with 1–2 good reps left. 4+ left = too light; form breaks = too heavy.

Feel it somewhere else? Fix it like this

  • Feel it in ShouldersElbows drifting forward and the shoulders lifting. Keep the elbows at your sides and lighten the weight.
  • Feel it in Forearms / gripWrists curling in. Keep the wrists straight and loosen the grip slightly.
  • Feel it in Lower backSwinging the torso. Stand against a wall or sit, and use a weight you can lift without momentum.
  • Barely felt itToo light or too fast. Lower for 3 seconds, pause 1 second at the stretch, and pick a load that leaves only 1–2 reps in the tank.
  • Joint painSharp or joint pain is a stop sign: end this set, lower the weight, shorten the range — if it repeats, switch to an easier variation.

During a workout we ask after the first set where you felt it and give the fix right away — and remember it for next time.

Tips

  • Use about 60–70% of your normal curl weight — the burn builds fast.
  • Count in groups of seven so you don't lose track.
  • Use 21s at the end of an arm session as a finisher.

Common mistakes

  • Swinging the weight as fatigue sets in during the final seven.
  • Cutting the half reps short or rushing between segments.

Breathing

Exhale on every lift and inhale on every lowering, keeping a steady rhythm.

Equipment needed

Dumbbell
Not owned

Recommended by goal

Build muscle3–4 sets × 8–12 reps · rest 60–90 s
Strength4–5 sets × 4–6 reps · rest 2–3 min
Endurance2–3 sets × 15–20 reps · rest 30–45 s

Variations of this move

Alternatives for the same muscle

See all