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Ergonomic Considerations of Manually Harvesting Maine Wild Blueberries
Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan www.asabe.org
Citation: Journal of Agricultural Safety and Health. 4(1):43-57 . (doi: 10.13031/2013.15347) @1998
Authors: C. Fairfield Estill, S.Tanaka
Keywords: Blueberries,Tendinitis, Musculoskeletal disorders, Harvesting
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.
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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 examinations, 10% had
some hand/wrist pain accompanied by a positive Phalens or Tinels test (consistent
with carpal tunnel syndrome), or a positive Finkelsteins test (consistent with de
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.