Philadelphia — Overuse injuries on the job can lead to elevated inflammation levels, mood changes and chronic pain, results of a recent study suggest.
A team led by Temple University researchers trained a group of rats to reach and pull a lever for a food reward until they reached 55% of their maximum voluntary pulling force. The rats were then placed into two groups. One performed high-repetition, low-force tasks for six weeks with a goal of four reaches per minute at 15% of maximum pull. Meanwhile, the other group rested.
Findings show that certain cytokines, a type of signaling protein, increased 200% to 500% in the flexor muscles, forearm bones and median nerves of the repetitive reach group. Those tasks “triggered a multilevel inflammatory cascade” that matched lasting pain-like and sickness behaviors.
By week six, the rest group had partially recovered from losing about 20% of baseline grip force, but grip weakness lingered. The task group remained 25% weaker than the rest group.
The researchers see the rise in inflammation as the link to weakness, hypersensitivity, fatigue and social withdrawal that workers often report after overuse injuries. They recommend therapies that reduce inflammation in musculoskeletal tissues, which can accelerate the rehabilitation process, limit sick leave and lower the costs of work-related musculoskeletal disorders.
The study was published in the journal Frontiers in Physiology.
