Ergonomic Considerations of Manually Harvesting Maine Wild Blueberries

Abstract

In July 1993, the National Institute for Occupational Safety and Health (NIOSH) received a request for a health hazard evaluation from the Maine Department of Human Services. NIOSH was asked to investigate musculoskeletal conditions, in particular wrist disorders (informally called “rakers' tendinitis”) which were reported among harvesters who raked wild blueberries in Maine.

Annually thousands of seasonal workers rake wild blueberries in various parts of Maine, mostly in the month of August. A field survey consisting of a symptom questionnaire, limited physical examinations, and ergonomic assessment of raking was conducted at a blueberry grower and processor in Maine.

A convenience sample of 134 rakers was recruited on-site over a three-day period in late August. Their median age was 30 (range: 13 to 69); 73% of participants were males; 10% of the participants were children (age 13 to 17). Participants reported moderate to severe pain, which was felt after the start of raking in the back (14%), in the hand/wrist (12%), and in the elbow (8%). On physical examination, 10% had some hand/wrist pain accompanied by a positive Phalen's or Tinel's test (consistent with carpal tunnel syndrome), or a positive Finkelstein's test (consistent with de Quervain's disease).

Ergonomic analysis of raking revealed that rakers worked mostly in stooped posture and frequently carried loaded buckets (up to 13 kg each). The metal rakes varied in size (42 to 47 cm wide) and weight (1.2 to 2.3 kg). The typical raking motion involved a constant firm grip on the handle, and repetitive ulnar (toward the little finger) and radial (toward the thumb) deviations of the wrist. The force of lifting the rake through the blueberry bushes was estimated to be 87 Newtons (S.D. ± 17.5), and the motion was repeated 32 times/min (S.D. ± 13). These repetitive and forceful motions could cause friction on the tenosynovium and explain a high prevalence of tendinitis. Recommendations for improvements to the rake and raking methods are suggested.

Full article can be found in: Journal of Agricultural Safety and Health
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