Pullups are one of the most iconic, and simultaneously difficult, exercises that exist. They have a number of benefits overall, including the fact that they rely only on bodyweight and therefore do not need special equipment or machines (aside from a bar or a surface above the head on which to grasp). Many people avoid these exercises because they are quite difficult, but this difficulty is an indication that the pullup is an exercise with great potential to improve your fitness in many ways.
1. Latissimus Dorsi
Your latissimus dorsi muscles, also known as "lats," are the muscles that receive the greatest benefit from a set of pullups. These muscles run from the top and outside of each shoulder and down the back. As you contract your arms and pull yourself up in the motion of the pullup, the latissimus dorsi muscles are the ones primarily responsible for making this motion. Therefore, they are likely to be the set of muscles most benefited by this exercise; conversely, they are also the most likely to be injured if the exercise is done incorrectly.
Rhomboid muscles are those that are present in the back, adjacent to the latissimus dorsi muscles. In their support of the lats, they also receive a great workout when you engage in a set of pullups. Helping to strengthen your back is an important part of strengthening your front and core, as well. Many people overlook the fact that the back muscles, which are in opposition to the stomach muscles, are vitally important for maintaining an even balance of strength throughout your upper body.
3. Arm Muscles
One of the great benefits of pullups is that they work a variety of muscles simultaneously. Unlike some other types of exercises, which focus on bending one joint only and therefore only work one muscle in particular, pullups make use of many muscles and joints. Your forearm muscles, biceps, and triceps will all have to engage in order to bend your arms at the elbow and accomplish the lifting motion that makes up the pullup. Thus, all of these various muscle groups will also benefit from a set of pullups as well.
4. Cardiovascular Workout
In addition to being an effective strength building exercise, the pullup is also highly effective as part of a cardiovascular workout. Engaging in pullups is likely to increase your heartrate. In order for cardiovascular exercise to be most effective, it should be continued for approximately 30 minutes or more. While most people will not engage in pullups continuously for 30 minutes, a set of pullups can be part of a longer circuit of exercises. When these exercises are performed quickly and with no resting period in between, they can constitute an excellent cardiovascular workout as well as a strength building period too.
For more information about the fitness benefits of pullups and how to successfully execute this exercise, consult with a trainer or gym representative.