Pull-ups are one of the best resistance exercises you can do. Few exercises call the same attention as someone who is doing a lot of push-ups or doing some variations based on push-ups. These are exercises that require a large part of the upper body area and the central force to be completed. The difficulty of the pull-ups can now be easier or more difficult, thanks to the weight belts that are attached to a weight or dumbbell plate (more difficult), or thanks to the assisted push-up machine (more easy).
The main muscle that is used to make a pull-up is the latissimus dorsi (lat). The main function of the bibs is either to bring the arms to the body or the body to the arms. In the case of a pull-up the arms are bringing the body.
There are a handful of secondary muscles used in the pull-up all of which are in the arms. The most important is probably the long supinator, the largest of the forearm muscles. The supinator is crucial for elbow flexion and evidence of its use can be seen when a flexion is initiated, since the muscle in the upper arms protrudes almost instantly.
Biceps and triceps
What comes as a surprise to many is that not only the biceps are stabilizing muscles in the pull-ups but also the triceps. Because biceps are also involved in elbow flexion, they are clearly involved in exercise, but not to the extent that many believe. The biggest surprise for many is that the triceps are also involved. However, because the long head of the triceps joins the scapula and the humerus, one of its actions is similar to that of the lats.
A handful of other muscles are involved and are known as synergists, which means they are needed to aid in movement in order to obtain maximum efficiency. The list includes the muscles in the forearm (brachial), the back (greater round, rhomboid, lower trapezius, levator scapula), chest (pectoralis major and minor) and shoulders (posterior deltoid).