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Session: Poster session I
Session starts: Thursday 24 January, 15:00

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Adhi Wibawa (University of Groningen, University Medical Center Groningen)
Nico Verdonschot ()
J.P.K. Halbertsma ()
M.S. Andersen ()
R.L. Diercks ()
Bart Verkerke ()

Abstract:
This study focused on validating muscle activities predicted by the AnyBody Modeling System (AMS) against measured muscle activity (EMG) from ten healthy subjects who performed a normal walking task. The GaitLoweExtremity Model (GLEM) from AMS was used in this study. Eight EMG electrodes measured the activity of eight different muscles of the right leg: Vastus Medialis (VM), Vastus Lateralis (VL), Rectus Femoris (RF), Semitendinosus (ST), Biceps Femoris (BF), Gastrocnemius Medialis (GM) and Lateralis (GL) and Tibialis Anterior (TA). Four different thresholds were applied on both curves (predicted and measured muscle activity): 10%, 25%, 35% and 45% of the mean of the RMS envelope threshold (MRET) before they were compared quantitatively in the same threshold level. Number of onset, offset, hills and duration of muscle activity were used to quantify the level of agreement. For the parameters number of onset, offset and hills, the weighted kappa method was used. Concordance correlation coefficient analysis was used for parameter duration of muscle activity. Visual inspection showed good agreement between EMG and predicted muscle activity. Quantifying the muscle activity by using number of onset/offset, number of hills and duration of muscle activation showed that, in general, for all parameters, the 45 % MRET showed the best agreement compared to the other MRET. For the number of onset and offset, two muscles (TA and VL) showed a fair agreement (0.20 < kappa value < 0.40) and four muscles showed a slight agreement (0 < kappa value < 0.20), the other two muscles (VL and ST) showed a poor agreement (kappa value < 0). For the number of hills, two muscles (GM and TA) showed a fair agreement and five muscles showed a slight agreement while only one other muscle (VM) showed a poor agreement. For the duration of muscle activity, all muscles showed poor agreement (concordance correlation value < 0.90). This first attempt in a quantitative point of view showed that the parameter number of hills was the best result. The differences between AMS and EMG patterns can be attributed to the nature of the AnyBody modeling process, the choice of parameters and the absence of a gold standard to compare the results with.