Your voice is a 'bag of muscles'. The larynx is the hollow muscular organ forming an air passage to the lungs, and contains the vocal cords. These muscles can also suffer from repetitive strain injury.
The TUC handbook, Keeping well at work, gives examples of how straining your voice can lead to serious injury, and what you can do about it.
Just One More Click: Doggy drama about staying safe online at work.