Participatory ergonomic intervention versus strength training on chronic pain and work disability in slaughterhouse workers: study protocol for a single-blind, randomized controlled trial

BACKGROUND: The prevalence of musculoskeletal pain in the shoulder, arm and hand is high among slaughterhouse workers, allegedly due to the highly repetitive and forceful exposure of these body regions during work. Work disability is a common consequence of these pains. Lowering the physical exposure through ergonomics intervention is the traditional strategy to reduce the workload. An alternative strategy could be to increase physical capacity of the worker through strength training. This study investigates the effect of two contrasting interventions, participatory ergonomics versus strength training on pain and work disability in slaughterhouse workers with chronic pain. METHODS/DESIGN: 66 slaughterhouse workers were allocated to 10 weeks of (1) strength training of the shoulder, arm and hand muscles for 3 x 10 minutes per week, or (2) participatory ergonomics involving counseling on workstation adjustment and optimal use of work tools (~usual care control group). Inclusion criteria were (1) working at a slaughterhouse for at least 30 hours per week, (2) pain intensity in the shoulder, elbow/forearm, or hand/wrist of at least 3 on a 0–10 VAS scale during the last three months, (3) pain lasting for more than 3 months, (4) frequent pain (at least 3 days per week) (5) at least moderate work disability, (6) no strength training during the last year, (7) no ergonomics instruction during the last year. Perceived pain intensity (VAS scale 0–10) of the shoulder, elbow/forearm and hand/wrist (primary outcome) and Disability of the Arm, Shoulder and Hand (Work module, DASH questionnaire) were measured at baseline and 10-week follow-up. Further, total muscle tenderness score and muscle function were assessed during clinical examination at baseline and follow-up. DISCUSSION: This RCT study will provide experimental evidence of the effectiveness of contrasting work-site interventions aiming at reducing chronic pain and work disability among employees engaged in repetitive and forceful work. TRIAL REGISTRATION: ClinicalTrials.gov:NCT01671267