This paper presents an overview of theories concerning the development of RSI (repetitive strain injury), related to muscle disorders. Movement is a noisy process. The level of noise is affected by factors such as fatigue and psychosocial stress. In order for precision movements to be made in such situations, an increased level of muscle activity is required. Positive feedback loops through γ-motoneurones may be responsible for these increases in muscle activity. The Cinderella hypothesis suggests that damage may take place even when muscle activity is of low intensity, due to locally high levels of muscle load. An increase in calcium concentration in muscle cells during long periods of muscle activity may act as a mechanism of this damage. Optimisation of task demands and the prevention of continuous activation of the same groups of muscles appear to be effective measures in the prevention of RSI.