Each year soft tissue injuries or musculoskeletal disorders (MSDs) associated with manual lifting and awkward, repetitive use of the lower back account for approximately 28% of the occupational injuries and illnesses reported to the Bureau of Labor Statistics (BLS, 2000). Most safety professionals, when performing ergonomic evaluations, are adept at identifying the key stressors that cause or aggravate MSDs (e.g. postures, force and repetition). Normally, qualitative methods such as checklists are employed and occasionally quantitative methods such as use of the National Institutes of Occupational Health and Safety (NIOSH) Revised Lifting equation is used. However, while checklists serve to identify risk factors, they fail to provide a rigorous quantitative analysis that is repeatable and scientifically validated. On the other hand, the use of the revised NIOSH lifting equation can be very intrusive to the operations and time consuming to the client and the safety and health professional. Beyond NIOSH provides an overview of the alternative methods that can be used for characterizing lifting hazards. Four alternative quantitative methods are reviewed and compared to the NIOSH lifting results for several cases to determine variability based upon each method's limitations.
Although technology has advanced in industrial production techniques, manual handling of materials in most instances has remained essentially the same. Many jobs still require some handling and a small percentage require extensive manual materials handling. In 2000, lower back injuries related to manual material handling accounted for 467,235 lost workday cases reported to BLS (2000). In addition to their sheer numbers, back injuries result in a disproportionate number of lost workdays compared to other work-related injuries. The combination of higher than average disability rates and rising medical costs have made MSDs the largest job-related injury and illness problem in the United States today. Back strains and sprains account for nearly 25.57% of the money spent for workers' compensation each year (Liberty Mutual 2002 Safety Index). In addition to the staggering direct costs of back strains and sprains, the indirect costs can be greater! As a result, quantifying the lifting hazards in an efficient and timely manner can aid the safety practitioner in determining the controls that should be implemented to minimize the risks.
In 1981, NOSH developed an equation to rate lifting tasks in terms of whether loads were excessive. A revised version of the equation was published in 1993 (Waters et al., 1993) and is considered by many to be the "Gold Standard" by which lifting hazards are quantified. The objective of the lifting equation is to prevent or reduce the occurrence of lifting-related low back pain and injury among workers. The revised equation expanded the number of tasks that can be evaluated by providing methods for evaluating asymmetrical lifting tasks, lifts of objects with less than optimal hand-container couplings and also guidelines for longer work durations and lifting frequencies.
