The pull up is a taxing exercise which primarily targets the latissimus dorsi (often referred to simply as the "lats"), the large muscle which spans much of the upper back. The movement also recruits a number of other muscles of the upper back, including the teres major, rhomboids, trapezius, and the rear head of the deltoid (back of the shoulder). The arm flexor muscles, including the biceps, are involved, but to a lesser extent than during a chin up where the athletes palms are facing towards the body placing the biceps in a mechanical advantageous position.
Once an athlete can perform the required number of repetitions with their own body weight, additional weight can be added via the use of a dipping/chinning belt. The belts attach around the waist of the athlete and allow weight plates to be secured, adding resistance to the pull up.
For athletes who struggle to perform body weight pull ups, the assisted pull up machine is a great way of building up strength. The counter-weight machine allows the athlete to perform the chin up in an assisted manner, and as the athletes’ strength progresses the counter-weight can be reduced until the athlete can perform the pull up with their own body weight.
The pull up is a highly effective exercise for athletes to develop upper back strength, power and size. The pull up, which differs from a chin up which has a supinated (under hand) grip, targets the large latissimus dorsi muscle of the upper back. Additional upper back muscles are also exercised, including the teres major, rhomboids and rear deltoid head. The arm flexors also play a role as the arm flexes during the pull up, but less biceps recruit occurs compared to the chin up due to the mechanically weak position they are placed in due to the over hand grip.
Performing the pull up on an assisted machine is a great way of gym-goers to take advantage of this great exercise, despite not yet having the strength levels required to perform a body weight pull up. The counter-weight allows the athlete to build up their strength levels over time, eventually reaching enough strength to perform the pull up without any counter-resistance.