(From ErgoWeb Listserve) Rest pauses. Research has shown that the frequency of rest pauses determines their effectiveness. The greater the frequency of the pauses the greater their effectiveness. It has shown that a pause 3 minutes long taken whenever fatigue becomes noticeable can reduce fatigue dramatically and increase productivity by 11% (Cakir, Hart and Stewart, 1979). In addition micropauses should be taken during the course of the work cycle. Many ergonomists believe that a rest break should be at least 5 minutes long for maximum benefit. WorkCover New South Wales issued a bulletin on keyboard work (No. 160687/9) states that keying work should not be prolonged for periods of over 40 minutes without rest. According to Pheasant (in his book "Ergonomics, Work and Health") for most types of work there is an upper limit to the length time that an activity can be performed efficiently. This duration of peak activity is termed the actile period. Its length depends on circumstances but it is generally between 30 minutes and 45 minutes. It is advisable to at least have a rest break at the end of this period to maintain performance and reduce fatigue. It might not be wise to recommend pause exercises instead of rest pauses especially if they have not been carefully evaluated by field trials. One survey of physical exercises for VDU operators concluded that some of them posed safety hazards because they exacerbated the work-related biomechanical stresses or because they were contra-indicated for certain medical conditions (Lee, Swanson, Sauter, Wickstrom, Waikar and Mangum, 1992). Many disrupted work too much and a fair number (about a third of them) were likely to be too conspicuous or embarrassing to perform. Static muscular effort reduces performance and cannot be sustained indefinitely. The length of time that can static effort can be maintained depends on the level of effort. An application of maximal force can be maintained for about 10 seconds, a moderate level of effort for about 1 minute and a slight effort for about 4 minutes (Grandjean, 1985). Research has shown that that a person can only exert about one fifth of the maximal force after 8 minutes of static effort (Monod quoted in Grandjean). Current research suggests that prolonged application of this level of force leads to musculoskeletal disorders and overuse injuries. On this basis posture should be changed frequently (preferably every 8 minutes or more often) and if awkward work postures cannot be altered frequent rest breaks are advisable. References: 1. A. Cakir, D. Hart and T. Stewart, (1979) "Visual Display Terminals", pages 247-253. 2. NSW Department of Industrial Relations and Employment, (1988), "Occupational Health Management for Keyboard Workers Occupational Overuse Syndrome" (Occupational Health and Safety Bulletin No: 160687/9), Lidcombe, March 1988. 2. S. Pheasant, (1991), "Ergonomics, Work and Health", (Basingstoke: The Macmillon Press). 3. K. Lee, N. Swanson, S. Sauter, R. Wickstrom, A. Waikar and M. Mangum, (1992), "A review of physical exercises recommended for VDT operations", Applied Ergonomics, vol. 23, no. 6, pages 387-408. Regards, David McFarlane Ergonomist, Health and Community Services Team. WorkCover Authority of New South Wales Level 5, 400 Kent Street, Sydney 2000, Australia E-mail: [EMAIL PROTECTED] <mailto:[EMAIL PROTECTED]>
