Pull-ups primarily work out the Latissimus Dorsi, also known as "wings". These are the muscles on the outsides of your upper back. They also provide a secondary workout for the Biceps, Rhomboids (top, middle back), Trapezius (middle, central back), the neck, and nearly every muscle in the forearms (Brachioradialis, Brachialis). Doing pull-ups also builds extremely powerful grip-strength. If you have experience lifting weights, pullups are most similar to a lat-pulldown machine. However, they are not exact
ly the same. When you do pullups and you hang from a bar, you must stabilize your body from rocking forward and backward- this requires a lot of effort from your abdominal and leg muscles.
In addition to standard pullups, There are many variations of pull-ups. Two of the most popular variations are: wide-grip and underhanded pull-ups. Wide-grip pull-ups shift most of the workout to the Latissimus Dorsi, and less to the secondary and stabilizer muscles. They are performed the same as regular pull-ups, except the hands are placed further out to the sides, and away from the body.
Underhanded pull-ups are also very similar to standard pull-ups. Simply turn your hands around so that your palms are facing you, and do a pull-up. You will immediately feel that a great deal of the workout has been shifted from your Latissimus Dorsi to your biceps. Underhanded pullups are good for beginners to build strength before attempting standard pullups.