Single Arm Dumbbell Fly
In SetGrip: Dumbbell Fly (Single Arm)
- Secondary muscles
- Delts
- Body part
- Chest
- Position
- Lying
- Laterality
- Unilateral (one arm at a time)
- Category
- Strength
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Working one arm at a time on the flat bench reveals exactly how much stronger one pec is than the other, and the off-center dumbbell makes your trunk brace against rolling for the whole set. Match total reps per side and lead with the weaker arm; it makes a useful periodic audit of your two-arm dumbbell fly.
How to do the Single Arm Dumbbell Fly
- Sit on a flat bench with a dumbbell in one hand, resting it on top of your thigh.
- Lie back on the bench, keeping the dumbbell pressed against your thigh.
- Using your free hand, help lift the dumbbell up to the starting position.
- Hold the dumbbell directly above your shoulder with your arm extended and palm facing inward.
- Lower the dumbbell out to the side in a wide arc, keeping a slight bend in your elbow.
- Pause when your arm is parallel to the ground, then reverse the movement and bring the dumbbell back to the starting position.
- Repeat for the desired number of repetitions, then switch arms and repeat.
Tip: Imagine hugging a barrel rather than pushing a weight.
Muscles worked
Primary
Pectorals · Chest
On chest flies and cable crossovers the pecs pull the arms together in an arc and should feel a deep stretch at the bottom and a hard squeeze at the top.
Secondary
- Delts — Rear delt flies work the back of the shoulder as the arms swing wide, and the front delt assists on any chest fly.
Common mistakes
- Elbows bending as you tire — this turns a fly into a press; set the elbow angle at the start and keep it constant for the whole set.
- Going too heavy — flies are a stretch and squeeze movement, not a strength lift; you should be able to pause at the bottom without the shoulders rolling forward.
- Stopping short of the stretch — let the arms open until you feel the chest or rear delts lengthen, then bring them back under control.
- Not squeezing at the finish — the last few inches are where the muscle shortens most, so hold the contraction for a count before opening again.
Sets, reps and where it fits
| Goal | Sets × reps | Rest |
|---|---|---|
| Muscle growth | 3–4 × 10–15 per side | 60–90 s |
| Endurance / finisher | 2–3 × 15–20 per side | 45 s |
| Strength | Not ideal — pick a compound lift for the same muscle | — |
Flies are an isolation movement for after the pressing or rowing is done. Pair a cable crossover with a cable rear delt fly on the same station, or dumbbell chest flies with dumbbell rear delt flies on the same bench.
Variations and alternatives
Similar exercises
Frequently asked questions
What muscles does the Single Arm Dumbbell Fly work?
The Single Arm Dumbbell Fly primarily works the pectorals. It also involves the delts, which assist the movement and stabilise the joints.
Is the Single Arm Dumbbell Fly good for beginners?
It is rated intermediate, so it suits people who already train regularly. Beginners can still do the Single Arm Dumbbell Fly with light load and a spotter or coach watching the first few sessions; if it feels awkward, pick an easier variation from the alternatives below first.
What can I do instead of the Single Arm Dumbbell Fly?
If you cannot do the Single Arm Dumbbell Fly, try the Decline Single Arm Dumbbell Fly, the Dumbbell Fly or the Stability Ball Single Arm Dumbbell Fly. Each of them trains the pectorals through a similar movement, so you can swap them in without changing the rest of the workout.
How many sets and reps should I do?
It depends on your goal. For the Single Arm Dumbbell Fly, a sensible starting point is muscle growth: 3–4 × 10–15 per side with 60–90 s rest; endurance / finisher: 2–3 × 15–20 per side with 45 s rest. Do it after your compound lifts. It is a finishing movement, not the main event.
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