Chest / Intermediate / Isolation (single joint)

One-Arm Flat Bench Dumbbell Fly

A single-arm fly on a flat bench that isolates the chest and challenges the core to resist rotation.

At a glance

Primary

Chest

Secondary

Front delts, Obliques, Abs

Equipment

Dumbbells, Bench

Movement pattern

Fly / hug, Anti-rotation (brace)

Level

Intermediate

Type

Chest, Isolation (single joint), One side at a time

Loads the shoulder. Use a load you can control and skip it if it causes pain.

How to do it

1. Lie on a flat bench holding a dumbbell in one hand above your chest, palm facing in and elbow slightly bent.
2. Lower the dumbbell out to the side in a wide arc until you feel a stretch in your chest.
3. Bring it back up over your chest along the same arc.
4. Complete the set and switch arms.

Tips

• Brace your core so your torso does not roll.
• Keep the elbow angle fixed.

Common mistakes

• ✗ Lowering heavy dumbbells far below the chest.

  Why it hurts: Long arms at full stretch put a big lever on the shoulder and pec tendon, a common way to tear it.

  ✓ Instead: Use light weights, keep a slight elbow bend and stop when the elbows are level with the torso.

• ✗ Bending the elbows more and more until it is a press.

  Why it hurts: The arm angle changes under load and the shoulder loses its stable position.

  ✓ Instead: Fix the elbow angle at the start and keep it through the whole rep.

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