Hyght Dumbbell Fly

Lie flat on a bench with a dumbbell in each hand, palms facing each other.

Extend your arms straight up over your chest, with a slight bend in your elbows.

Keeping a slight bend in your elbows, lower the dumbbells out to the sides in a wide arc until you feel a stretch in your chest.

Pause for a moment, then reverse the movement and bring the dumbbells back to the starting position.

Repeat for the desired number of repetitions.

Recruiting larger muscle groups to "help" move the weight instead of isolating Pectorals — swinging momentum or shifting the torso takes tension off the muscle this exercise is meant to train.

Locking out too fast or letting the elbows drift outward under load — controlling the eccentric (lowering) phase is where most of the muscle-building stimulus happens.

Letting the two arms/sides move independently with different ranges of motion or tempo, which hides side-to-side strength imbalances instead of fixing them.

Skipping a warm-up set at lighter load/intensity — even "beginner" exercises benefit from a rehearsal set to groove the movement pattern before working sets.