Do manual workers with persistent lifting-related LBP show different trunk muscle activity compared to manual workers...

To investigate if manual workers with and without a history of LBP show different trunk muscle activity during repeated lifting? And explore if pain or fatigue is related to trunk muscle activity in people with LBP during repeated lifting?

This study compared peak and average muscle activity between manual workers with LBP (n = 21) and without a history of LBP (n = 16) during lifting. A box of 10% of the participant's body mass was lifted from the floor at a self-selected speed and posture. A 12-sensor trunk muscle surface electromyography (sEMG) protocol was used to compare peak and average muscle activity over 100 lifts. This lifting task induced pain and fatigue; therefore, associations between trunk muscle activity, pain and fatigue in manual workers with LBP could be explored. Peak and average muscle activity over a 100-lift task were used.

There were no differences in trunk muscle activity between groups. Associations between muscle activity and pain or muscle activity and fatigue in manual workers with LBP were rare (4 of 96 tests of association were statistically significant). Peak abdominal muscle activation was consistently low at 12 to 31% of maximal voluntary contraction (MVC) throughout the lifting task in both groups, whereas peak paraspinal muscle activation was around 33 to 59% of MVC.

At a group level, trunk muscle activity during lifting does not differ between people with and without a history of LBP. In this study, neither repetition, pain, nor fatigue had a consistent effect on trunk muscle activity during lifting. These sEMG results question the importance of trunk muscle activity during lifting in people with lifting-related LBP with low levels of pain and disability.