Set an incline bench to 45–60 degrees and sit back with a dumbbell in each hand, arms hanging down with palms facing inward (supinating to face forward as you curl).
Keep your upper arms stationary against the bench pad and curl both dumbbells upward, rotating palms toward your shoulders at the top.
Squeeze the biceps at peak contraction, keeping elbows fixed.
Lower the dumbbells slowly back to the hanging position with control.