reckonerDumbbell biceps curl
One bell in each hand, alternating or together, and a wrist that is free to turn. That freedom is the point: a dumbbell lets you finish the rep in full supination, which is the position that gets the most out of the biceps1.
Elbows still, no swinging the bells.
- Pattern
- Arm isolation
- Trains
- Biceps
- Kit
- Dumbbell
- Loading
- A weight you choose
- Reckoner prescribes
- 3 sets of 10 to 15 reps at RPE 8
- Progression step
- 1 kg once the top of the range is clean
- Skill
- Simple to learn
- Recovery cost
- Very low
- Not prescribed if you have declared
- Elbow
Muscles worked
How to do it
Stand tall with the bells at your sides
Feet hip width, arms hanging, palms facing your thighs. Ribs down and shoulders back. Nothing above your elbows has a job in this exercise.
Curl and turn the palm up as you go
Start turning the hand from the first few inches so the palm is fully up by the time the forearm is halfway. That turn is where the difference lives: the fully supinated grip beat neutral and palms-down grips on biceps excitation at the same load1.
Finish just past vertical, elbows still
Bring the bell up until the forearm is a little past vertical and stop. Elbows still, no swinging the bells, which is the cue on your wrist.
Lower under control to a straight arm
Let the palm turn back as you go down, and finish with the elbow fully open. Take longer over this half than the way up.
What goes wrong
Starting the palm already turned up
Holding full supination from the bottom removes the turn, which is most of what a dumbbell offers over a bar. Start with the palms facing in and let the rotation happen while the elbow bends.
Leaning back into the last few reps
The torso tips and the bells swing up on momentum. It looks like two more reps and it is two fewer. Stand still, or stand against a wall if you cannot.
Chasing the strong arm
One side is usually ahead, and matching it on the weaker side means the weaker side swings. Run both at what the weaker arm can do properly and let it close the gap.
How Reckoner progresses this lift
Six weeks of this lift, from 12 kg, run through the real engine. Nothing below was typed in: the prescription, the decision and the sentence beside it all come from the same code that writes your week.
| Week | Prescribed | What it did |
|---|---|---|
| 1 | 3 x 10 at 12 kg | More reps 10 → 11 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 2 | 3 x 11 at 12 kg | More reps 11 → 12 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 3 | 3 x 12 at 12 kg | More reps 12 → 13 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 4 | 3 x 13 at 12 kg | More reps 13 → 14 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. |
| 5 | 3 x 14 at 12 kg | Deload 40% of sets offFive weeks of building, then one week lighter. About 40% of the sets come off. The load holds and your reps stay where you earned them, so you keep the strength and lose the fatigue. |
| 6 | 2 x 14 at 12 kg | More reps 14 → 15 repsYou finished every set at RPE 7, with room left in the range, so the reps climb before the load does. The lighter week is over, so this is back to three sets. |
Real engine output, not an illustration. Every row was produced by running the engine itself when this page was generated.
The full rule, and why the reps move before the load does, is in how Reckoner decides to add weight.
Questions people ask
Alternating or both arms at once?
Either. Alternating gives each arm a rest between reps and takes twice as long. Both together is quicker and makes it harder to swing one arm without noticing. There is no evidence that one grows more muscle than the other.
Is one arm at a time better than a barbell curl?
Not for size. Across nine pooled studies, unilateral and bilateral training produced no significant difference in muscle growth, and strength gains followed whichever way each group trained2. Dumbbells are useful for the rotation and for sorting out a side that is behind.
How heavy should these be?
Light enough that the elbow does not travel and the last rep is the same shape as the first. The step in this movement is small on purpose, because a curl has a much smaller strength reserve than the lifts around it.
Similar movements
Reckoner eases the load first when this lift stalls, and offers one of these only if it stalls again after that. A lift already as light as your kit goes has no load left to ease, so the offer comes straight away. Each of them has a page.
Sources
- Coratella and colleagues, Sports, 2023. Biceps brachii and brachioradialis excitation in biceps curl exercise: different handgrips, different synergy ten competitive male bodybuilders curling a cable at an eight repetition maximum with supinated, neutral and pronated grips, with biceps brachii excitation in the lifting phase greater with the supinated grip than the neutral by twelve per cent and than the pronated by nineteen, and brachioradialis excitation also greater with the supinated grip than either of the others, and no significant grip differences in the lowering phase
- Kassiano and colleagues, Sports Medicine, 2025. Comparison of muscle growth and dynamic strength adaptations induced by unilateral and bilateral resistance training: a systematic review and meta-analysis nine studies pooled, finding no significant difference in muscle growth between training one limb at a time and training both, and strength gains that follow specificity, bilateral training favoring bilateral tests and unilateral training favoring unilateral ones