This carefully performed, randomized, controlled, single-blinded trial comes from Denmark. The investigators studied the effect of strength training on slaughterhouse workers with chronic upper limb pain.
Sixty-six workers with upper extremity pain intensity of at least 3 out of 10 and duration of at least 3 months and no treatment within the last year were divided into two equally sized groups that were evenly matched for age, body habitus, and baseline pain levels and strength measurements.
The strength-training group received supervised twice weekly exercise sessions for 10 weeks. The resistance exercises included shoulder rotation in 2 planes with elastic tubing, radial/ulnar wrist deviation with a sledge hammer, wrist extension and flexion with a wrist roller, finger flexion with a hand gripper, and finger extension using hand bands. The repetitions and resistance were advanced as the weeks progressed.
The control group received ergonomic training (exposure reduction) with focus on hands-on, task-specific activities.
All subjects received the following tests both at the start and at the end of the 10 week trial:
Pain intensity on a 10 point visual analog scale
Maximum grip strength
Fatigue resistance: time until forceful grip fell to 50% of maximum grip strength
Self-rated health question: “How do you rate your overall current health?”
Fear avoidance question: “Fast and forceful arm movement exacerbates pain in my shoulder, arm or hand?”
The investigators were blinded regarding whether the subjects were in the treatment or control group.
For all tests, the exercise group had statistically significant improved results compared to the control group.
The authors note that no adverse events such as dropping weights on toes or developing exercise-related sharp pains occurred, implying that the exercise program seemed safe for slaughterhouse workers with chronic upper extremity pain.
Study strengths included the randomized, controlled study design and blinded examiners. Study limitations included incomplete data for some subjects in each group and the questionable value of a single fear-avoidance question to adequately address that issue.
Finally, the researchers caution that their inclusion/exclusion criteria restrict the application of their results to manual workers performing repetitive and vigorous tasks and who have chronic upper extremity pain.
This was a carefully designed and performed study. The results appear valid. The authors appropriately caution that the results do not necessarily apply to other types of work or to other body regions. The strengthening program proved safe and could be easily implemented in other settings. Interested in giving it a try?