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Dumbbell Chest Fly

Also called: Flat dumbbell fly

Primary muscles: Pectoralis major

Secondary muscles: Deltoid

Joints / actions: Glenohumeral joint (horizontal adduction)

Plane: transverse

Equipment: dumbbells, bench

What it is

Lying on a bench, opening the arms out to the sides with a slight elbow bend, then bringing the dumbbells back together over the chest.

Purpose

Isolates the pectoralis major through horizontal adduction with less triceps involvement than pressing.

Starting position

Lie on a flat bench holding a dumbbell in each hand above the chest, palms facing each other, elbows slightly bent.

Step by step

  1. Keeping a fixed slight elbow bend, lower the dumbbells out to the sides in a wide arc.
  2. Stop when you feel a comfortable stretch across the chest (about level with the torso).
  3. Bring the dumbbells back together over the chest, squeezing the chest muscles.

Breathing

Inhale as you lower the arms; exhale as you bring them together.

Coaching cues

"Hug a big tree." Keep the elbow angle constant — the movement is at the shoulder, not the elbow.

Common mistakes

Turning it into a press by bending the elbows; going too deep or too heavy and straining the shoulder; shrugging.

Easier regression

Reduce range/weight, or use a machine (pec deck) for a guided path.

Harder progression

Slow the lowering phase or add a brief pause in the stretched position with controlled load.

Alternatives

Cable crossover, pec-deck machine.

Who may benefit

People wanting to emphasize the chest with a joint-friendly moderate load.

Who should modify or avoid it

Those with shoulder pain in the stretched position should limit range or substitute.

Why this exercise works

By keeping the elbows fixed, the movement happens almost entirely at the shoulder as horizontal adduction — the pectoralis major's specialty — so it targets the chest with little triceps help.

⚠ Safety note

Use a moderate weight; the stretched position is where the shoulder is most vulnerable. Reduce range if it pinches.

Sources

“Horizontal adduction of the arm is produced primarily by the pectoralis major.”

Anatomy and Physiology 2e — OpenStax, Rice University · Ch. 11.5 Muscles of the Pectoral Girdle and Upper Limbs

Peer-reviewed textbook · License: CC BY-NC-SA 4.0 · Last checked 2026-07-19

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