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Dumbbell One Arm Bench Fly

A single-arm dumbbell fly on a flat bench that isolates one pec at a time and adds a core anti-rotation demand.

ChestDumbbellHorizontal adduction

Primary

Pectoralis major

Secondary

Anterior deltoidCore stabilizers

Equipment

Dumbbell

Pattern

Horizontal adduction

Setup

  1. 01Lie flat on a bench holding one dumbbell.
  2. 02Press the bell up over the chest, palm facing inward.
  3. 03Place the free hand on the hip or bench for balance.
  4. 04Set the feet flat and brace the trunk.

Execution

  1. 01Lower the arm out to the side in a wide arc.
  2. 02Keep a slight, fixed bend in the elbow.
  3. 03Stop when the arm is level with the chest.
  4. 04Sweep the bell back up over the chest.

Checkpoints

  • -The elbow bend stays constant through the whole arc.
  • -Hips and shoulders stay square on the bench.
  • -The arm lowers to chest level, not below.
  • -The dumbbell finishes above the chest, not the face.

Common mistakes

  • -Twisting the torso toward the working arm.
  • -Bending the elbow more at the bottom to cheat the load.
  • -Dropping the arm too deep and straining the shoulder.
  • -Pressing the weight up instead of sweeping it.

Programming notes

  • -Use 2 to 3 sets of 10 to 15 reps per arm.
  • -Slow 3-second lowering maximizes the stretch on the pec.
  • -Use lighter loads than a two-arm fly to control rotation.

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