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 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 for the shoulder and chest respectively). Due to this leverage, fly exercises of all types have a large potential to damage the shoulder joint and its associated ligaments and the tendons of the muscles connecting to it. They should be done with caution and their effects first tested while using very light weights; which are gradually incremented after more strength is gained.