A machine fly, alternatively called a seated lever fly or "pec deck" fly is a

strength training Strength training, also known as weight training or resistance training, is exercise designed to improve physical strength. It is often associated with the lifting of Weightlifting, weights. It can also incorporate techniques such as bodyweigh ...

exercise based on the free weight chest fly. 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#Characteristics, koala (which has two thumb#O ...

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 ...

move through an arc while the

elbow The elbow is the region between the upper 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 t ...

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

muscle Muscle is a soft tissue, one of the four basic types of animal tissue. There are three types of muscle tissue in vertebrates: skeletal muscle, cardiac muscle, and smooth muscle. Muscle tissue gives skeletal muscles the ability to muscle contra ...

s of the upper body, primarily the sternal head of the pectoralis major. Because these exercises use the arms as

lever A lever is a simple machine consisting of a beam (structure), beam or rigid rod pivoted at a fixed hinge, or '':wikt:fulcrum, fulcrum''. A lever is a rigid body capable of rotating on a point on itself. On the basis of the locations of fulcrum, l ...

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 and

bench press The bench press or chest press is a weight training exercise where a person presses a weight upwards while lying horizontally on a weight training bench. The bench press is a Compound movements, compound movement, with the primary muscles involved ...

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 are used as synergists in both variations. The

biceps brachii The biceps or 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 to form a single muscle bell ...

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