The incline butterfly, which is also commonly referred to as incline chest fly, is an upper body weight training exercise. Usually it’s completed with a pair of dumbbells, but some fitness gyms offer incline butterfly machines. Incline butterfly involves movement at only one joint, which means it’s considered an isolation exercise.
Exercise Technique
The incline butterfly is completed on a bench set to about a 45-degree angle. To perform an incline butterfly, sit on the bench and recline back, resting your head on the bench. Place your feet firmly on the floor. Hold a dumbbell in each of your hands. Begin with your arms extended up toward the ceiling so that the weights are directly over your chest line with your palms facing each other. Keep a slight bend in the elbows and lower the dumbbells out to your sides. Continue down until you feel a slight stretch in your shoulders and then return the weights back to the starting position. According to the American Council on Exercise, the incline butterfly can also be completed while standing by using a pulley cable system.
Primary Muscle
According to ExRx.net, the primary muscle involved in the incline butterfly is the clavicular head of the pectoralis major. The pectoralis major has two heads, including the sternal, which is the largest section, and the clavicular head, which is smaller and located at the very top of your chest. The muscle originates at the front of your clavicle and then runs out toward your shoulders and inserts at the front of your humerus bone. The clavicular head of the pectoralis major can perform a variety of movements at the shoulder joint, including transverse flexion, transverse adduction, internal rotation, adduction and flexion. However, as you complete the incline butterfly, the muscle strictly performs transverse adduction and transverse flexion of the shoulder, which means it brings your arms toward the center of your body on a transverse plane.
Assisting Muscles
Also recruited during the incline butterfly are the anterior deltoid and the biceps brachii. The anterior deltoid, which is the front of your shoulder muscle, assists with shoulder flexion. The biceps brachii contracts to flex your elbows, or create the slight bend in your elbow joints.
Stabilizing Muscles
There are also muscles that isometrically contract in order to stabilize your joints while you’re performing an incline butterfly. Isometric contraction means that the muscle contracts to hold a static position. Your biceps brachii and brachialis isometrically contract to maintain a set flexion in your elbow joint, preventing your elbows from collapsing and straightening as your arms lower down toward the floor and raise back up again. Your wrist flexors isometrically contract to keep your wrist joints stable and prevent them from extending due to the weight of the dumbbells.
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