Ergonomic Assessment Of Manual Materials Handling And The Recommended Lifting Weight Limit

Although automation and other technological development have dramatically reducedthe need for manual material handling (MMH), there is a widespread use of manualhandling operation. The MMH tasks are highly associated with adversemusculoskeletal disorders (MSDs), such as low back pain (LBP), discomforts of otherbody parts, fatigue, and the attributed injuries. LBDs represent the most common andmost costly musculoskeletal disorder experienced in the workplace. Up to 80% ofadults will eventually experience back pain at some time during their life and 4-5% ofthe population has an acute low back pain episode every year. Estimates of annualcosts for LBD have been as high as US$100 billion.Epidemiologic methods have been used to identify occupationally related physicalrisk factors in a variety of industries. Bernard (1997) and Hoogendoorn et al. (1999)performed critical reviews of many of these studies. Traditionally, most epidemiologicstudies have investigated the risk contribution of: (1) heavy physical work, (2) liftingand forceful movements, (3) bending and twisting, (4) whole-body vibration and (5)static work postures. The critical reviews have found strong evidence of LBP riskassociation for the lifting and forceful movements, bending and twisting, as well asthe whole-body vibration risk factors. More moderate evidence or risk association wasidentified for heavy physical work. However,the literature did not support arelationship between static work postures and LBP.Manual materials handling (MMH) tasks include listing, lowering, pushing, pulling,holding. and carrying materials. Examples include loading materials in manufacturingsettings, moving patients in hospitals, and delivering parcels and packages.Furthermore, since the requirement for load carrying is more widespread indeveloping and underdeveloped countries than in developed countries, research onthese countries' populations, such as Chinese populations, becomes very important.In order to define acceptable task demands relative to worker capacity, various criteriahave been developed based upon the principles of biomechanics, physiology andpsychophysics. The US National Institute for Occupational Safety and Health(NIOSH) developed an equation in 1981 and revised it in 1991 to assist safety and 3复旦大学博士学位论文 英文摘要health practitioners in evaluating lifting demands. These lifting guidelines are beingwidely used by occupational health practitioners because they provide an empiricalmethod for evaluating manual lifting tasks.It is not surprising that criteria based on the principles of biomechanics,psychophysics, and physiology often provide MMH limits that are in conflict.Furthermore, the feasibility and accessibility of these criteria is unclear for applying inChinese population because of a smaller body size and lifting capacity. Unfortunately,few epidemiological and experimental studies have been conducted to assess the linkbetween exposure levels and related adverse health effects in Chinese population.The purposes of the study attempt to establish a ergonomic evalution approach forMMH, validate the feasibility of NIOSH lifting equation used in Chinese workingpopulation; and to set up the acceptable proposal for design of safe lifting tasks.To investigate lifting-related musculoskeletal disorders, NORDIC questionnairesinterview, OWAS postural analysis were applied to a machinery manufacturingpopulation. the study subjects consisted of 69 workers mainly involved in manualmaterials handling, categorized as Job A; and 51 machinery workers, served ascontrols, which were less MMH task involved, as Job B.Surface electromyography (sEMG) is a non-invasive method of analysis of the degreeof muscular activity and function. It can be used to assess the overall functional statusof muscles and can be done simultaneously on identical contralateral mu...