Do the Pec Fly Machine & Dumbbell Flyes Work the Same Muscle?

Movements at the shoulders are similar when working out on the pec fly machine and performing the dumbbell fly exercise. Because of this, the muscles recruited to handle most of the load are similar between the two exercises. However, due to slight variations between the two movements, they do differ on which smaller assisting muscles are recruited.

  1. Similar Exercise Techniques

    • Both the pec fly machine and dumbbell fly involve holding your upper arms in a horizontal position and bringing them toward the centerline of your body. Pec fly machines can either place you in a seated or lying position. With your arms held out to your sides and forearms positioned against the pads, you squeeze your upper arms towards the centerline of your body so the pads meet in the front of your chest. You open your arms back out until they return to the starting position. When you’re doing the fly exercise with dumbbells, you lie on your back on a flat bench. With a dumbbell in each hand, begin with your arms pointed vertical with your palms facing each other. While keeping just a slight bend in your elbows, open your arms out until your upper arms are parallel to the floor, and then squeeze them back together until they’re pointed vertical again.

    Shared Recruited Muscle

    • The shared movement at the shoulders is referred to as horizontal adduction. The muscle that is responsible for performing this movement at the shoulders is the pectoralis major, which is the major muscle in the chest. The pectoralis major, which originates at your sternum and shoots out to each of your shoulders, is considered the primary mover for both exercises.

    Assisting Muscles Involved During Pec Fly Machine

    • Unlike during the dumbbell fly, while your shoulders are horizontally adducting on the machine, your scapulas are simultaneously protracting. This means the outside edges of the scapulas are moving forward and away from the spine. To handle this movement, your serratus anterior and pectoralis minor muscles are recruited.

    Dumbbell Fly Assisting Muscles

    • The dumbbell fly exercise requires your shoulders to perform a bit of flexion, which means your upper arms rise in front of you slightly as you squeeze your upper arms together. This movement is courtesy of your anterior deltoid, which is the front section of the major muscle in your shoulders. In addition, to keep the slight bend in your elbows as you lift and lower your arms, your biceps brachii contracts.