Trunk Muscle Performance and Work-Related Musculoskeletal Disorders among Manual Lifting with Back Belt Wearing...

to determine the effects ofback belt use on trunk muscle performance and the association between those performance outcomes with Work-Related Musculoskeletal Disorders (WMSDs).

All manual lifting workers in one grocery distribution, warehouse center were interviewed about the history of illness, back injury, WMSDs, lifting manner and experience of back belt use. They were assessedfor trunk muscles performance including the flexion (F), the extension (E) and the right and left side bridge (RSB and LSB) endurance test and Exercise Level of Lumbar Stabilization test (ELLS). Pearson s correlation and Spearman's rank correlation statistics were used to determine the association.

One hundred and seven males, aged 18 to 42 years participated in the study. Most participants had ELLS at levels 2 (31.1%) and 3 (30.2%). The mean F, E, RSB and LSB endurance times were 62.33, 88.62, 77.17 and 77.33 seconds, respectively. The greatest area of WMSDs was the lower back (53.33%). Significant correlations were found between the ELLS and RSB (r = 0.244, p = 0.012) and between the ELLS and LSB (r = 0.199, p = 0.041). Significant correlations were found between pain scale of backpain and ELLS (r = -0.299, p = 0.016). Significant correlations were found between the number of WMSD areas and trunkflexion endurance (r = -0.263, p = 0.007), right trunk endurance (r,= -0.195, p = 0.044), left trunk endurance (r = -0.325, p = 0.001) and endurance ratio of RSB/LSB (r(s) = 0.224, p = 0.022). Furthermore, most participants (84.1%) had imbalanced endurance of RSB/LSB. Duration andfrequency ofback belt use did not correlate with any trunk muscle performance. This may have been because few participants did not wear belts (10.1%) or wore belts sometimes (26.6%).

Low correlation was found between back belt use and WMSDs. To prevent back injury, the lifting workers should be trained to balance their trunk muscles endurance, especially right and left trunk muscles and to stabilize their lower back while lifting.