A fly is a strength training

Strength training

Strength training is the use of resistance to muscular contraction to build the strength, anaerobic endurance, and size of skeletal muscles. There are many different methods of strength training, the most common being the use of gravity or elastic/hydraulic forces to oppose muscle contraction...

 exercise in which the hand

Hand

A hand is a prehensile, multi-fingered extremity located at the end of an arm or forelimb of primates such as humans, chimpanzees, monkeys, and lemurs...

 and arm

Arm

In human anatomy, the arm is the part of the upper limb between the shoulder and the elbow joints. In other animals, the term arm can also be used for analogous structures, such as one of the paired forelimbs of a four-legged animal or the arms of cephalopods...

 move through an arc

Range of motion

Range of motion , is the distance that a movable object may normally travel while properly attached to another object. It is also called range of travel, particularly when talking about mechanical devices and in mechanical engineering fields...

 while the elbow

Elbow

The human elbow is the region surrounding the elbow-joint—the ginglymus or hinge joint in the middle of the arm. Three bones form the elbow joint: the humerus of the upper arm, and the paired radius and ulna of the forearm....

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

Muscle

Muscle is a contractile tissue of animals and is derived from the mesodermal layer of embryonic germ cells. Muscle cells contain contractile filaments that move past each other and change the size of the cell. They are classified as skeletal, cardiac, or smooth muscles. Their function is to...

s of the upper body

Torso

Trunk or torso is an anatomical term for the central part of the many animal bodies from which extend the neck and limbs. The trunk includes the thorax and abdomen.-Major organs:...

. Because these exercises use the arms as lever

Lever

In physics, a lever is a rigid object that is used with an appropriate fulcrum or pivot point to either multiply the mechanical force that can be applied to another object or resistance force , or multiply the distance and speed at which the opposite end of the rigid object travels.This leverage...

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

Military press

The military press is a variation of the overhead press weight training exercise using very strict form.The military press targets the deltoid muscles in the shoulders as well as the triceps...

 and bench press

Bench press

The bench press is an exercise of the upper body. For bodybuilding purposes, it is used to stimulate the pectorals, deltoids, and triceps. While on his or her back, the person performing the bench press lowers a weight to the level of the chest, then pushes it back up until the arm is straight...

 for the shoulder and chest respectively).

Equipment

Flies can be performed using any weight that can be held in the hand. The simplest equipment to use is a dumbbell

Dumbbell

The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs .-History:...

, though they can also be performed using a cable machine

Cable machine

A cable machine is an item of equipment used in weight training or functional training. It consists of a rectangular, vertically-oriented steel frame about 3 metres wide and 2 metres high, with a weight stack at each end. The cables that connect the handles to the weight stacks run through...

 and sitting or standing upright. When using a cable machine, the hands and arms move through the same anatomical plane as the dumbbell version. Using dumbbells for pectoral flies requires the use of stabilizer muscles associated with performing flies, when compared to performing flies with a cable machine

Cable machine

A cable machine is an item of equipment used in weight training or functional training. It consists of a rectangular, vertically-oriented steel frame about 3 metres wide and 2 metres high, with a weight stack at each end. The cables that connect the handles to the weight stacks run through...

.

Chest fly

The chest or pectoral fly primarily works the pectoralis major muscle

Pectoralis major muscle

The pectoralis major is a thick, fan-shaped muscle, situated at the chest of the body. It makes up the bulk of the chest muscles in the male and lies under the breast in the female...

s to move the arms horizantally forward. If medially (internally) rotated, it is assisted in this by the anterior (front) head of the deltoideus in transverse flexion. If laterally (externally) rotated, the contribution of the deltoid is lessened and the pec major is strongly emphasized as the transverse adductor.

The hands are usually brought out further than the elbows, in which case the flexors contract isometrically to inhibit undesired excess flexion of the elbow. Muscles which do this are the biceps brachii, the brachialis and the brachioradialis

Brachioradialis

Brachioradialis is a muscle of the forearm that acts to flex the forearm at the elbow. It is also capable of both pronation and supination, depending on the position of the forearm...

. The biceps may also play a limited role in shoulder flexion. The straighter the elbow is, the more stretch in these muscles. For safety, many avoid locking out the joint.

The movement is performed lying on the back on a bench

Bench (weight training)

A weight training bench is a piece of equipment that has a resemblance to a normal bench, but is designed for use in weight training....

, starting weights extended above the chest, meeting at the midsagittal plane. The arms are lowered through an arc passing through the transverse plane

Transverse plane

The transverse plane is an imaginary plane that divides the body into superior and inferior parts. It is perpendicular to the coronal and sagittal planes....

, terminating when the arm is roughly parallel

Parallel (geometry)

Parallelism is a term in geometry and in everyday life that refers to a property in Euclidean space of two or more lines or planes, or a combination of these. The assumed existence and properties of parallel lines are the basis of Euclid's parallel postulate. Two lines in a plane that do not...

 to the floor, then returning to the starting position and repeating.

This exercise can be done using other implements than dumbbell

Dumbbell

The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs .-History:...

s, such as kettlebell

Kettlebell

The kettlebell or girya is a cast-iron weight used to perform ballistic exercises that combine cardiovascular, strength and flexibility training.Sizes may range from to...

s or weight plates. There are also machines such as the pec deck which perform a stabilized version of the movement while allowing people to sit upright.

If using a cable machine, the body leans forward to counterbalance the weight moved, with the feet braced and the elbows are positioned slightly below shoulder height. The arms move the same arc as a bench fly, relative to the torso

Torso

Trunk or torso is an anatomical term for the central part of the many animal bodies from which extend the neck and limbs. The trunk includes the thorax and abdomen.-Major organs:...

.

Inverted fly

The inverted fly (also known as a bent-over lateral raise, reverse fly or rear delt fly) works the posterior

Anatomical terms of location

Standard anatomical terms of location are designations employed in science that deal with the anatomy of animals to avoid ambiguities that might otherwise arise. They are not language-specific, and thus require no translation...

 deltoid

Deltoid muscle

In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the central...

. This movement is the opposite of a chest fly. The exercise is performed with the torso parallel to the ground, facing down, with the hands in front of the face. Arms are moved through the transverse plane

Transverse plane

The transverse plane is an imaginary plane that divides the body into superior and inferior parts. It is perpendicular to the coronal and sagittal planes....

 in an arc until parallel to the ground (or the limit of the range of motion

Range of motion

Range of motion , is the distance that a movable object may normally travel while properly attached to another object. It is also called range of travel, particularly when talking about mechanical devices and in mechanical engineering fields...

 of the shoulder

Shoulder

The human shoulder is made up of three bones: the clavicle , the scapula , and the humerus as well as associated muscles, ligaments and tendons. The articulations between the bones of the shoulder make up the shoulder joints. The major joint of the shoulder is the glenohumeral joint, which...

 is reached), then returned to the starting position and repeated.

In terms of glenohumeral movement, the posterior deltoid does not work alone, and is assisted by other muscles. If the shoulder is neutrally rotated (elbows pointing outward then towards the scapulae as they lift) the posterior deltoid will be assisted in this transverse extension by the lateral rotators of the rotor cuff: the infraspinatus and teres minor. If the shoulder is externally rotated (elbows pointing towards the hips) then it will be assisted in this transverse abduction by the middle deltoid head.

This fly, while it seems like an isolation movement, is actually a compound movement because it involves movement in a second joint: the scapulothoracic. The scapulae will retract (adduct) during this type of fly. The muscles that perform this function are the rhomboids

Rhomboids

Rhomboids can refer to:* Rhomboid muscles** Rhomboid major muscle** Rhomboid minor muscle...

 and the trapezius.

If the lifter drops their elbows closer to their hips (rather than bringing them outward) the latissimus dorsi will come into play and deemphasize the use of the aforementioned muscles that cross both joints, as the lats bypass the scapulae and attach directly to the lumbar fascia.

A variation involves sitting upright and using a cable machine

Cable machine

A cable machine is an item of equipment used in weight training or functional training. It consists of a rectangular, vertically-oriented steel frame about 3 metres wide and 2 metres high, with a weight stack at each end. The cables that connect the handles to the weight stacks run through...

; the machine is next to the shoulder opposite the muscle being worked (in line with the coronal plane), and the hand moves through the transverse plane across the front of the body at approximately eye level.

Shoulder fly

The shoulder fly (also known as a lateral raise) works the deltoid muscle

Deltoid muscle

In human anatomy, the deltoid muscle is the muscle forming the rounded contour of the shoulder. Anatomically, it appears to be made up of three distinct sets of fibers though electromyography suggests that it consists of at least seven groups that can be independently coordinated by the central...

 of the shoulder. The movement starts with the arms straight, and the hands holding weights

Dumbbell

The dumbbell, a type of free weight, is a piece of equipment used in weight training. It can be used individually or in pairs .-History:...

 at the sides or in front of the body. Arms are kept straight or slightly bent, and raised through an arc of movement in the coronal plane that terminates when the hands are at approximately shoulder height. Weights are lowered to the starting position, completing one "rep". When using a cable machine the individual stands with the coronal plane in line with the pulley

Pulley

A pulley, also called a sheave or a drum, is a mechanism composed of a wheel on an axle or shaft that may have a groove between two flanges around its circumference. A rope, cable, belt, or chain usually runs over the wheel and inside the groove, if present...

, which is at or near the ground. The exercise can be completed one shoulder at a time (with the other hand used to stabilize the body against the weight moved), or with both hands simultaneously if two parallel pulleys are available.

This movement, when the shoulder is kept in neutral rotation, primarily targets the middle head of the deltoid. The anterior (front) and posterior (back) heads of the deltoid will also co-contract to aid in the abduction function. If the shoulder is laterally (externally, outwardly) rotated, the anterior deltoid becomes the prime mover of the glenohumeral joint, the posterior deltoid de-activates, and the middle head assists.

If repetitions are done explosively, it is possible for form to deteriorate and other muscles may come into play to do work instead of the deltoid, by generating upward and rotation momentum. The muscles which can be used to "cheat" in this movement are primarily the serratus anterior and the upper fibers of the trapezius, both of which elevate and upwardly rotate the scapulae.

See also

• Bench press
  Bench press
  The bench press is an exercise of the upper body. For bodybuilding purposes, it is used to stimulate the pectorals, deltoids, and triceps. While on his or her back, the person performing the bench press lowers a weight to the level of the chest, then pushes it back up until the arm is straight...
  
   - a compound alternative to a chest fly.
• Bent-over row
  Bent-over row
  A bent-over row is a weight training exercise that targets a variety of back muscles. Which ones are targeted varies on form. The bent over row is often used for both bodybuilding and powerlifting...
  
   - a compound alternative to a reverse fly.
• Supine row
  Supine row
  The supine row is an exercise in weight training. This exercise primarily works the muscles of the upper back, these muscles are the Trapezius and Latissimus dorsi, the supine row also works the Biceps as a secondary muscle group...
  
   - a bodyweight, compound alternative to a reverse fly.
• Upright row
  Upright row
  The upright row is a weight training exercise performed by holding a barbell with the overhand grip and lifting it straight up to the collarbone. This is a compound exercise that involves the trapezius, the deltoids and the biceps. The narrower the grip the more the trapezius muscles are exercised,...
  
  - a compound alternative to a shoulder fly.