Ergonomic evaluation of an apple picking bucket intervention designed to reduce musculoskeletal strain in orchard harvest workers.

摘要

Previous research has shown that back and shoulder musculoskeletal strain is a significant occupational health problem affecting migrant orchard harvest workers. The author has developed a simple intervention to reduce back and shoulder strain while picking apples. In order to evaluate this intervention, three studies were conducted.;In the first study, researchers sought to identify measures of muscle fatigue for use in a subsequent field study. In the laboratory, the timed arm hold test, (35.7% time reduction), and the timed spinal extension, (31.8% time reduction), showed statistically significant fatigue. In the orchard, only the timed arm hold, (11.4% time reduction), showed significant fatigue. The potential effect of field conditions and subject motivation on these results needs further exploration.;The orchard study evaluated the hip belt's effectiveness in three areas: intervention acceptance, effects on worker productivity, and one-day muscle fatigue of the back and shoulder. One hundred two New York apple harvest workers were randomly assigned to use the intervention hip belt or placebo belt for one week. In a second week all workers switched conditions. Ninety-one percent of the subjects favored the intervention hip belt. Use of the intervention did not appreciably slow picking speed. However, the anticipated ergonomic benefits of the intervention were not demonstrated using the timed arm hold and the standing spinal extension tests.;The third study employed alternative means to evaluate the effect of intervention. Surface electromyography is a method able to detect subtle changes in muscle activity. Electromyographic measurements on 15 muscles were taken from 10 laboratory volunteers who were carrying a full bucket of apples, once while wearing the intervention belt, and once without the intervention.;Significant reductions in amplitude favoring the intervention were seen for 11 of 15 muscles, mostly in the middle and lower back. These intervention versus control differences were seen with both bucket carrying positions (front vs. side) and tended to increase with increasing flexion angle. Thus, the use of the intervention belt reduces electromyographic amplitude (indicative of muscle activity) among a number of mid- and lower-back muscles. This is suggestive of a protective effect against back strain.