Repetitive movements can cause injury in workers performing a variety of jobs, but analyzing worker technique and muscle activity in relation to the workstation can provide answers to how an injury is incurred and how to prevent it in the future.
With the assistance of surface electromyography (SEMG), an ergonomic analysis of worker behavior, posture, and movement can be conducted. The SEMG is a biofeedback instrument to measure muscle tension. The use of SEMG allows muscle function to be assessed in a manner that is objective and reproducible.
The Winter 2010 issue of the journal Biofeedback, published by Allen Press Publishing Services, Lawrence, Kan, describes the case study of pressmen working at print facilities of a major news publishing company. Ergonomic analysis identified excessive workplace injuries to the neck and shoulder, most commonly the rotator cuff on the right side.
Three activities were then targeted for intervention: blanket washing, newsprint roll handling, and predrive belt positioning wheel adjustments. With the use of SEMG, researchers determined whether improvements to the workstation, worker technique, or both were more likely to lower the risk of injury while performing these tasks.
Data were collected by using two active electrodes placed parallel to the targeted muscles. Muscles studied included the left and right upper trapezius and the left and right lumbar paraspinals.
The researchers found that some of the workers’ movements might save time, but not injury. While washing the blanket cylinder, for example, a worker would typically put one hand on the control panel to manipulate the inch-safe buttons and simultaneously reach for the cylinder with the other hand. These actions require awkward movements that make the muscles work harder.
One solution was to retrain the worker not to perform these tasks simultaneously. By keeping the noncleaning arm at rest, the cleaning task could be performed less strenuously. Alternatively, the researchers introduced a metal pole about 4 feet long with two ergonomic handles and a cleaning head. Through SEMG assessment, this supplement to the workstation combined with a modification of worker behavior brought about an even greater reduction in strenuous muscle activity while the worker performed the same task.
Click here to read the full text of the article, titled Surface Electromyography-Assisted Ergonomic Analysis in a Newspaper Printing Plant: A Case Study,” Biofeedback, Volume 38, Issue 4, Winter 2010.
[Source: Allen Press Publishing Services]