Development and evaluation of an EMG-based model to estimate lumbosacral loads during seated work

Low back pain (LBP) is a common occupational problem and continues to be the leading cause of occupational disability. Among diverse known risk factors, sitting is commonly considered as an important exposure related to LBP risk, and modern living and contemporary work both involve increasing sedentary behaviors including more frequent and prolonged sitting. Specifically, a few studies have assessed lumbosacral loads in seated postures, but no sitting-specific model has been developed to investigate the effects of seated tasks and time-dependent variations in lumbosacral loading during sitting. Here, a three-dimensional, electromyography-based biomechanical model of the trunk was developed to predict lumbosacral loads during a range of seated tasks. This model was a modification of an earlier approach, and specific modifications included a revised representation of lumbar muscle anatomy and viscoelastic soft-tissue properties, and a method to account for muscular fatigue during prolonged sitting. With these enhancements, the predictive ability of the model was assessed over a range of seated tasks that differed in terms of lumbar posture, time pressure, and mental workload. Predicted model parameters corresponded well with values reported earlier. Reasonable levels of correspondence were found between external and predicted lumbosacral moments across all tested tasks. Physical exposures and injury risks related to seated work can potentially be estimated using this modeling approach, which may facilitate future injury prevention strategies.