In recent years studies have shown that very low levels of static loading are associated with muscle fatigue. Bjorksten and Jonssor have shown that static muscle work maintained for over 1 h should not exceed 5-6% of maximal voluntary contraction (MVC). Jonsson29 further suggested that static loading is acceptable only if it is lower than 2% of MVC when maintained for the entire working day. Grandjean quantifies static loading in three categories relating to the forces required. If a high force is exerted static muscle actions should be for less than 10 s; for a moderate force, less than 1 min, and for a low force, less than 4 min.