Musicians put their bodies through a lot. They practice for hours a day and, depending on the instrument played, engage certain parts of their bodies in repetitive type motions for long periods of time.
For instance, a pianist will sit or stand at a piano or keyboard, often in the same position for hours. A clarinet player must keep their head, neck, and jaw in a precise position in order to play properly. A guitarist must sit for long periods while holding the guitar in a certain position while moving their fingers over the frets in a very precise manner.