A pull-up is a kind of exercise that uses the weight of the body (body weight) to make a person stronger. To do this exercise, one should hold something that is high above the head with one or both hands so the person's body is hanging free under it in order to pull oneself up and stop when the chin is above the hands. This mostly helps the back muscles but also uses the muscles on top of the arms (biceps) and stomach (abdominals). It is an exercise that does not need any sophisticated equipment except some sort of bar a person can hold on.
Many different ways to position the wrists and hands are used. Some call them all different exercises, but they are actually similar. Some kinds of pull-ups use additional weights on a belt to make the exercise harder.
Those who use bad form on this exercise will kick with their legs or jump and jerk with the legs to help the motion. Good form is to hold the low parts of the body still and use only the arms to pull the body up.
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