A flat-bench dumbbell fly with one arm while the other hand grips the bench, letting you focus on each side of the chest while the core resists the pull to rotate.
Primary muscles
Secondary muscles
This information is general fitness guidance, not medical advice. Stop if you feel pain and consult a qualified professional.
Main muscles working (thicker lines)
Lie on a flat bench holding one dumbbell over your chest, palm facing in and elbow softly bent, and grip the side of the bench with your free hand.
Brace the core so the torso doesn't tip toward the weight.
Lower the dumbbell out to the side in a wide arc until you feel a stretch across the chest.
Squeeze the chest to bring the dumbbell back over the chest along the same arc.
Finish all reps, then switch arms.
Breathing: Inhale as the arm opens, exhale as you bring it back up.
Hips and shoulders stay square
Soft, fixed elbow
Lead with the chest
Rolling toward the dumbbell
Bending the elbow into a press
Going heavier than you can stabilise
Keep the load lighter than for a two-arm fly; the offset weight pulls you off the bench.