A validation study on muscle activity prediction of a lower limb musculoskeletal model using EMG during normal walking

This study focused on validating muscle activities predicted by the a Lower Limb musculoskeletal model of AnyBody Modeling System (AMS) against measured muscle activity (EMG) from ten healthy subjects who performed a normal walking task. The GaitLowerExtremity Model (GLEM) of AMS was used in this study. Eight EMG electrodes measured the activity of eight muscles of the right leg: Vastus Medialis, Vastus Lateralis, Rectus Femoris, Semitendinosus, Biceps Femoris, Gastrocnemius Medialis and Lateralis and Tibialis Anterior. Four different thresholds were applied on both curves (predicted and measured muscle activity): 10%, 25%, 35% and 45% of the mean of the graph threshold (MGT) before they were being compared quantitatively in the same threshold level. Number of onset and offset of muscle activity were used to quantify the level of agreement. Visual inspection showed good agreement between EMG and predicted muscle activity. In general, for all parameters the 45 % MGT showed the best agreement compared to the other MGT. For the number of onset and offset, two muscles showed fair agreement and four muscles showed slight agreement. This first attempt in a quantitative point of view showed that 6 muscles showed a slight positive agreement out of 8 in both variables number of onset and offset. The differences between AMS and EMG patterns can be attributed to the nature of the modeling process such as assumption and simplification, and possible inaccuracy of determining knee kinetic data during motion.