A machine fly, alternatively called a seated lever fly or "Pec Deck" fly is a

strength training Strength training or resistance training involves the performance of physical exercises that are designed to improve strength and endurance. It is often associated with the lifting of weights. It can also incorporate a variety of training te ...

exercise based on the free weight

chest fly A fly or flye is a strength training exercise in which the hand and arm move through an arc while the elbow is kept at a constant angle. Flies are used to work the muscles of the upper body. Because these exercises use the arms as levers at t ...

. As with the chest fly, the

hand A hand is a prehensile, multi-fingered appendage located at the end of the forearm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs. A few other vertebrates such as the koala (which has two opposable thumbs on each " ...

and

arm In human anatomy, the arm refers to the upper limb in common usage, although academically the term specifically means the upper arm between the glenohumeral joint (shoulder joint) and the elbow joint. The distal part of the upper limb between t ...

move through an arc while the

elbow The elbow is the region between the arm and the forearm that surrounds the elbow joint. The elbow includes prominent landmarks such as the olecranon, the cubital fossa (also called the chelidon, or the elbow pit), and the lateral and the m ...

is kept at a constant angle. Flyes are used to work the

muscle Skeletal muscles (commonly referred to as muscles) are Organ (biology), organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other ...

s of the

upper body The thorax or chest is a part of the anatomy of humans, mammals, and other tetrapod animals located between the neck and the abdomen. In insects, crustaceans, and the extinct trilobites, the thorax is one of the three main divisions of the crea ...

, primarily the sternal head of the

pectoralis major The pectoralis major () is a thick, fan-shaped or triangular convergent muscle, situated at the chest of the human body. It makes up the bulk of the chest muscles and lies under the breast. Beneath the pectoralis major is the pectoralis minor, ...

. Because these exercises use the arms as

lever A lever is a simple machine consisting of a beam or rigid rod pivoted at a fixed hinge, or '' fulcrum''. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, load and effort, the lever is d ...

s at their longest possible length, the amount of weight that can be moved is significantly less than equivalent press exercises for the same muscles (the

military press The overhead press is an upper-body weight training exercise in which the trainee presses a weight overhead while seated or standing. It is mainly used to develop the anterior deltoid muscles of the shoulder. The standing version was once a compon ...

and

bench press The bench press, or chest press, is a weight training exercise in which the trainee presses a weight upwards while lying on a weight training bench. Although the bench press is a full-body exercise, the muscles primarily used are the pectoralis ...

for the shoulder and chest respectively). Denie Walter is credited with calling it the Peck Dec back in the 1970s.

Equipment

There are two designs of weight training machines available for this exercise. The seated lever fly machine, and the Pec Dec. The seated lever fly involves grasping two handles at shoulder height, and pushing them together while keeping the elbows at a constant angle. When using the Pec Dec machine the hands grip two handles at head height, while the forearms push against two pads at chest height.Pec Dec fly
at exrx.com The anterior

deltoids The deltoid muscle is the muscle forming the rounded contour of the human shoulder. It is also known as the 'common shoulder muscle', particularly in other animals such as the domestic cat. Anatomically, the deltoid muscle appears to be made up o ...

are used as synergists in both variations. The

biceps brachii The biceps or biceps brachii ( la, musculus biceps brachii, "two-headed muscle of the arm") is a large muscle that lies on the front of the upper arm between the shoulder and the elbow. Both heads of the muscle arise on the scapula and join t ...

act as a synergist in the seated lever exercise, but not on the Pec Dec due to the raised arm position. In some machines, the seated lever can be adjusted to perform a rear delt fly exercise. Butterfly-machine-2.png, Butterfly machine fly (pec deck) start Butterfly-machine-1.png, Butterfly machine fly (pec deck) end

References

Weight training exercises {{Bodybuilding-stub