Electromyography as a measure of peak and cumulative workload in intermediate care and its relationship to musculoskeletal injury: An exploratory ergonomic study

Injury rates in Intermediate Care (IC) facilities are high and the factors related to these injuries are unclear. The objectives of this exploratory sub-study, which is part of a large multi-faceted study in 8 IC facilities are to: (1) evaluate EMG measured over a full-shift in the back and shoulders of 32 care aides (CAs) as an indicator of peak and cumulative workload (n=4×8 facilities); investigate the relationship between EMG measures and injury indicators; and explore the relationship between EMG measures and other workload measurements. Lumbar EMG was converted to predicted cumulative spinal compression and ranged in CAs from 11.7 to 22.8 MN s with a mean of 16.4 MN s. Average compression was significantly different during different periods of the day (p<0.001) with highest compression during pre-breakfast when CAs assist most with activities of daily living. Significant differences were found in average compression between low and high injury facilities for 3 of 5 periods of the day (p<0.010). Peak compressions exceeding 3400 N occurred for very little of the workday (e.g. 11.25 s during the 75 min period pre-breakfast). Peak neck/shoulder muscle activity is low (99% APDF ranged from 8.33% to 28% MVC). Peak and cumulative spinal compression were significantly correlated with lost-time and musculoskeletal injury rates as well as with total tasks observed in the CAs (p<0.01). Perceived exertion was only correlated with peak compressions (p<0.01). Facilities with low injury rates provided significantly more CAs (p<0.01) to meet resident needs, and subsequently CAs performed fewer tasks, resulting in less peak and cumulative spinal loading over the day.