A 72% drop in neck/shoulder pain symptoms occurred over a four-week period following the application of ergonomic interventions among a group of 247 Los Angeles sewing machine operators according to a recent prospective University of California study.
Multiple demographic, ergonomic, and psychosocial work-related factors were tracked to determine their influence on change in pain complaints. Analysis showed that pain symptoms had a:
- 20% greater reduction among workers who had a minimum of 35 rest minutes during the work day
- 16% greater reduction among workers who described their physical workload as low
- 24% less reduction among workers who claimed to have a high physical workload
- 18% less reduction among workers who put in overtime hours
Self reported neck/shoulder pain dropped greatly over the four-week period initially following the application of ergonomic interventions but tended to show little change from that benchmark in three subsequent pain assessments conducted at one month intervals.
The Bottom Line – How This Applies To Ergonomists
A 72% reduction in neck/shoulder pain following the application of ergonomic interventions provides a strong justification for ergonomic programs. Assuming worker productivity is directly related to worker well being, ergonomic solutions augment a company’s bottom line.
Further, this study revealed that an ergonomist should think broadly when applying controls. A minimum of 35 rest minutes per work day and low physical workload were positive influences on the change in neck/shoulder pain. Adverse pain modifiers were overtime hours and a high physical workload.
This repeated measures analysis showed that the interventions had a fast initial impact but quickly leveled off relative to reducing neck/shoulder pain.
Other Key Points
A previously published analysis of this study’s data showed that the intermediate and highest levels of intervention (described below in Research Method) were more effective relative to reducing neck/shoulder symptoms than the basic level. The highest level was most effective. Regardless of ergonomic intervention level, the pain score change was similarly affected by the demographic, ergonomic and psychosocial work-related factors.
Within this cohort group, 65.2% were female, 75.7% were Hispanic, 21.9% were Asian, and 11.3% described a history of musculoskeletal disorders (prior to the baseline interview).
Rest time of less than 50 minutes per day was reported by 54% of the study group.
From 13 garment shops in Los Angeles, California, 560 sewing machine operators were asked to participate in the investigation between October 2003 and April 2005.
To be considered for the study, a worker:
- Had to have worked three months or more
- Performed sewing machine work tasks for more than 20 hours per week
- Had plans to stay at their job for at least six months
- Was not on probation
- Did not have an active workers’ compensation claim
During the research process, the study cohort reduced to 480 workers representing 11 shops which eventually identified 247 volunteers with neck/shoulder pain.
Approximately one to two months after the baseline assessment, one of three levels of ergonomic intervention was randomly applied to the 480 workers:
- basic level – footrest, small storage box, side table, task lamp, and reading glasses
- intermediate level – task chair plus all the basic level equipment items
- highest level – chair custom designed for sewing machine operators plus all the basic level equipment items
After the intervention was applied, data was collected from the 247 neck/shoulder pain subjects at four week intervals over four months. The key factors of influence tracked included gender, age, ethnicity, musculoskeletal medical history, overtime work, number of sewing tasks performed, number of sewing machines operated over the previous four weeks, total rest time per day, job strain, social support, job dissatisfaction, and subjective physical demands.
The outcome of concern was change in neck/shoulder musculoskeletal pain in relationship to the tracked factors for each intervention level as revealed through repeat measuring (pain relative to each factor of influence) at the four four-week time intervals.
This study can be acquired at: wiley.com
Article Title: Follow-Up of Neck and Shoulder Pain Among Sewing Machine Operators: The Los Angeles Garment Study
Publication: American Journal of Industrial Medicine, 53:352–360, 2010
Authors: P C Wang, R J Harrison, F Yu, D M Rempel, and B R Ritz
This article originally appeared in The Ergonomics Report™ on 2010-03-29.