Chest · Isolation

Flat Dumbbell Fly

A chest isolation exercise using dumbbells on a flat bench, opening and closing the arms in an arc to stretch and squeeze the pectorals. The fly trains the chest's actual function, drawing the arms together across the body, and loads the stretched position more deeply than any press. It rewards light weight and patience, and punishes ego loading faster than almost anything else in the library.

By Macros Inc Team Verified by Alex Dedmon Updated August 2026

Beginner Dumbbell Isolation Push
flat-dumbbell-fly-poster
  • Level Beginner
  • Equipment Dumbbell
  • Primary Muscles Front Delts, Pectorals
  • Movement Isolation Push

Demonstration

Watch the Form Demo

Technique

How to Do the Flat Dumbbell Fly

  1. Lie on a flat bench holding light dumbbells over your chest, palms facing each other.
  2. Set a slight bend in your elbows and keep it fixed.
  3. Open your arms in a wide arc, lowering the dumbbells out to your sides.
  4. Descend until you feel a deep stretch across the chest.
  5. Reverse the arc, squeezing the chest to bring the dumbbells back over you.
  6. Stop just short of touching them together to keep tension on.

Anatomy

Muscles Worked

chest
Primary muscles
Pectorals
Secondary muscles
Front Delts

Do This

Form Cues

  • Keep a fixed slight bend in the elbows for the whole rep.
  • Open the arms in a wide arc until you feel a stretch, then reverse.
  • Stop the descent when the stretch peaks, not when the arms are level.
  • Imagine wrapping your arms around a barrel in both directions. The arc stays wide going down and coming up.

Avoid This

Common Mistakes

  • Bending the elbows and pressing rather than flying.
  • Lowering too far and dragging the shoulder into deep extension.
  • Clanging the dumbbells together at the top.
  • Adding weight before the stretch position is fully controlled, which is how flys earn their bad reputation with shoulders.

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