Specific Ergonomic Forces Associated with Musculoskeletal Disorders

Agricultural work varies significantly with the type of commodity and associated work practices. Certain types of work practices are strongly identified as being at greater risk for repetitive injuries, such as manual harvest of small vegetables and fruits, meat processing, and dairy farming. A 3-year, NIOSH-supported study focusing on identifying priority MSDs in California nurseries reported upper extremity and back injuries as the most commonly reported injuries. Job tasks with the highest risk of MSDs were considered to be propagation (cuttings), canning (transport to field), field work (pruning, spacing, and weeding), and shipping. Job analysis identified highly repetitive gripping, high pinch forces, contact stress, and awkward posture associated with the use of non-power hand tools and material handling, which characterize those job tasks (30).

An assessment of California vineyards by the University of California Ergonomics Research Center found a high proportion of jobs involving repetitive heavy lifting, bending, and stooping. Hand harvest risk factors included highly repetitive handgrip; exertion of high force to carry full tubs; multiple awkward positions involving the shoulders, forearms, and trunk; highly repetitive cutting and reaching; and moderate forceful exertions involving the shoulders and arms. Grapevine pruning involves a high level of muscular activity associated with hand-powered professional pruning shears and has been associated with musculoskeletal hand disorders, in particular paresthesias of the dominant hand (31,32).

In the northeastern United States, research has been conducted on ergonomic hazards for apple harvest workers. This type of hand labor exposes workers to weight-bearing hazards and awkward postures. The result is that back, neck, and shoulder strain are among the most common occupational health complaints seen at health centers within this population. A posture, activities, tools, and handling (PATH) methodology for quantifying ergonomic hazard exposure developed for industry has been adapted for orchard work. This PATH methodology is a validated work-sampling tool for quantifying ergonomic risk factors in jobs involving nonrepetitive work. In 2001 a PATH assessment of 14 apple harvest workers showed that they spent nearly two-thirds of the harvest observation period (62.9%) reaching and picking and 78.5% of the time bearing weight. Full apple bags in this study weighed up to 42 lb (19 kg), and ladders ranged from 10 to 25 lb (4.54 to 11.34 kg). The common postures and posture-load combinations observed were the arm, shoulders, and elbows elevated with and without loads. Comparison to PATH assessments of jobs in construction and nursing show apple harvest work to be at least as hazardous (see Chapter 6) (11,33-38).

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