A pull-up bar, also known as a chin-up bar, is a solid bar that is mounted at either end to fixed points, such as in a doorway. It is used to perform pull-ups and chin-ups, which are exercises that use the body's weight for resistance. A user will grasp the pull-up bar with his hands and pull the body upward, then lower the body back to the starting position to complete one repetition. A pull-up bar can be a simple, straight bar mounted in a doorway, or it can be a more versatile bar that has several hand positions and can be easily removed from the doorway when not in use.
The simplest version of the pull-up bar is the straight bar mounted directly to a doorway. Cups are mounted to either side of the doorway with screws, and the pull-up bar is placed inside the cups, thereby supporting the bar itself. Many bars expand outward to create a tighter fit within the cups; this is accomplished by twisting the two-piece bar, which is threaded to provide expansion. This type of pull-up bar sometimes features a layer of padding to provide comfort in the hands when performing a pull-up.
A more versatile version of pull-up bar is the removable or portable bar. This type of bar uses the body's weight to lock itself into position above a doorway rather than mounting screws. It can be removed after use and stored in a closet or other out of the way space. Such bars can feature one simple straight pull-up position, or it can feature several hand positions that allow the user to work different sets of muscles. These bars can also feature some padding for hand comfort and grip.
Gyms and fitness centers often have pull-up bars that are mounted to other pieces of exercise machinery. These bars are often found on larger pieces of exercise machinery that are intended for several different types of exercises, and more often than not, these bars feature more than one hand position for the user to grasp so he can work different sets of muscles. Some gyms also feature mounted pull-up bars that are not attached to other machines; they are instead mounted to a wooden frame that is fixed to a wall. This allows the user to perform pull-ups without interfering with another user's exercises, or vice versa. Some versions of the bar can be mounted directly to the ceiling, but these are less common and more difficult to install.