Dumbbell Fly's is an weight lifting exercise that primarily develops the chest (Pectoralis Major). Duwork your chest without the assistance of the triceps.

Muscles Worked When Performing Dumbbell Flys  

Target Muscles

• Pectoralis Major, Sternal

• Pectoralis Major, Clavicular
• Deltoid, Anterior
• Biceps Brachii, Short Head

• Biceps Brachii
• Brachialis
• Triceps Brachii
• Wrist Flexors

There is a specific form to the dumbbell fly which reduces the chance of injury and maximally challenges the muscles of the chest.

• Grasp two dumbbells.
  
• Lie supine on bench.
• Feet are kept flat on the floor, weight on the heels, lower leg perpendicular to the floor, with the buttocks always in contact with the bench. This prevents extreme arching of your lower back. Feet are kept flat on the ground or end of the bench a wide foot stance to increase stability on the bench.
• Pinch the shoulder blades together to avoid recruiting the anterior deltoid during the lift.
• Keep your chest up at all time. Don’t allow your chest to go flat or shoulders to roll forward. You’ll lose upper-back tightness, losing power & increasing risk of shoulder injury.
• Support dumbbells above the chest with the arms fixed in a slightly bent position.
  
• Internally rotate shoulders so elbows to the sides.
• Lower dumbbells to sides until chest muscles are stretched with elbows fixed (locked in position, slightly bent). The important thing to remember is to have a slight bend in the elbows, have the palms facing up during the movement, and pull your shoulder blades back together when you lower the weight so it takes strain off the rotator cuff.
• Bring dumbbells together in a hugging motion (like you are hugging a tree) until dumbbells are nearly together. Squeeze the pecs so that the shoulder blades should start moving away from each other because that is what the pecs do.
• Repeat.

The following errors are potentially dangerous and can result in injury. Avoid them at all costs.

• Not locking the elbows. You can pull ligaments and hurt your rotator cuff.

Incorrect form may lead to multiple types of injuries including:

• torn ligaments/tendons in shoulders.
• back injuries due to bridging, which is the arching of the lower back turning the bench press into the decline press. To prevent bridging, compress the stomach muscles to force the lower back down, or bring legs up and flat onto the bench.

Variations are intended to work different subgroups of muscles, or work the same muscles in slightly different ways:

• Angle - a dumbbell fly can be performed on an incline, on a decline, or on a stabilizer ball. The incline-version shifts some of the stress from the pectorals to the anterior deltoids and gives a greater stimulus to the upper pectorals, whereas the decline allows more weight to be lifted while using nearly the same musculature as the traditional bench press.

• Incline Dumbbell Fly. From an incline bench. Emphasis shoulders and upper chest.
• Decline Dumbbell Fly. From a decline bench. Allows more weight. Emphasizes more of the lower chest.