specific questions on MOtoNMS
Posted: Sun Sep 06, 2015 5:27 am
Thank you for your previous response to my questions. I have more detailed questions about MOtoNMS.
1) After executing dynamic elaboration, MOtoNMS generates two .mat file in the EMGs folder named as emg.mat and EMGsSelectedEnvelope in which emg.mat consists of normenv.mat. To the best of my understanding, the dimension of normenv.mat depends on the size of C3D file that has been cut and exported for analysis in MOtoNMS. However, the individual muscle plot in the EMGs folder seems to show the data corresponding to the length of stance phase in x-axis rather than the length of C3D file.
1.1) I was wondering if MOtoNMS generates any .mat file as an output that corresponds to the length of stance phase regardless of which method that has been chosen for analysis (e.g. compute stance phase, manual).
2) Most of the available EMG sensors have built in amplifier, bandpass filtering so additional software filtrations are not required to be performed. My question is if hardware band pass filter once has been applied to the signal, would not additional filtration (software) cause phase shift in the EMG signal? If yes, should we comment line 33 of EMGLinearEnvelpe function in data processing folder??
2.1) In this context, it has been recommended in some journal papers that data segmentation (sliding window with increments) must be performed before applying any sort of filtration to avoid phase shift. The window chosen for this type of segmentation is smaller than the stance phase detected by the thresholding algorithm. To the best of my knowledge, this has not been applied in MOtoNMS so I would like to know if this theory is valid and if it would be possible to implement it in MOtoNMS?
3) To consider electromechanical delay (EMD) in the signal, 0.2 s has been implemented before the IC/foot strike occurring according to the MOtoNMS manual. In the literature, the EMD delay of 30 to 100 ms were suggested [Conforto, S., et al. "How much can we trust the electromechanical delay estimated by using electromyography?." Engineering in Medicine and Biology Society, 2006. EMBS'06. 28th Annual International Conference of the IEEE. IEEE, 2006.].
So what is the reason the 0.2 seconds have been chosen? Is that based on any literature review?
3.1) Also in the manual, it has been stated that due to synchronisation of the markers, ground reaction forces and EMGs, EMD has been considered. So my question is what if the system (e.g. motion capture, GRF, foot switch and EMG) has already been synchronised together before the experiment was carried out. In that case,
Do we still need to take EMD into consideration? If yes, what value is suitable for lower limb muscles EMG recording?
3.2) This question is related to part 1.1 and 3.1 of my questions. Do muscle plots in the dynamicElaborations show the EMG signal that corresponds to the length of stance phase with consideration of 0.2 seconds EMD i.e. window is segmented 0.2 second before initial contact however, the plot only shows stance phase OR do they show the signal from the frame that corresponds to EMD (i.e the length of the plot is 0.2s+stance phase)??
**What I want to exactly understand is if stance phase (compute stance phase), or one gait cycle (manual analysis window) is the aim of the analysis, what would be the best value to be considered for electromechanical delay so the desired window shows the true (actual) EMG behaviour?
Thank you in advance for your response.
Pouyan
1) After executing dynamic elaboration, MOtoNMS generates two .mat file in the EMGs folder named as emg.mat and EMGsSelectedEnvelope in which emg.mat consists of normenv.mat. To the best of my understanding, the dimension of normenv.mat depends on the size of C3D file that has been cut and exported for analysis in MOtoNMS. However, the individual muscle plot in the EMGs folder seems to show the data corresponding to the length of stance phase in x-axis rather than the length of C3D file.
1.1) I was wondering if MOtoNMS generates any .mat file as an output that corresponds to the length of stance phase regardless of which method that has been chosen for analysis (e.g. compute stance phase, manual).
2) Most of the available EMG sensors have built in amplifier, bandpass filtering so additional software filtrations are not required to be performed. My question is if hardware band pass filter once has been applied to the signal, would not additional filtration (software) cause phase shift in the EMG signal? If yes, should we comment line 33 of EMGLinearEnvelpe function in data processing folder??
2.1) In this context, it has been recommended in some journal papers that data segmentation (sliding window with increments) must be performed before applying any sort of filtration to avoid phase shift. The window chosen for this type of segmentation is smaller than the stance phase detected by the thresholding algorithm. To the best of my knowledge, this has not been applied in MOtoNMS so I would like to know if this theory is valid and if it would be possible to implement it in MOtoNMS?
3) To consider electromechanical delay (EMD) in the signal, 0.2 s has been implemented before the IC/foot strike occurring according to the MOtoNMS manual. In the literature, the EMD delay of 30 to 100 ms were suggested [Conforto, S., et al. "How much can we trust the electromechanical delay estimated by using electromyography?." Engineering in Medicine and Biology Society, 2006. EMBS'06. 28th Annual International Conference of the IEEE. IEEE, 2006.].
So what is the reason the 0.2 seconds have been chosen? Is that based on any literature review?
3.1) Also in the manual, it has been stated that due to synchronisation of the markers, ground reaction forces and EMGs, EMD has been considered. So my question is what if the system (e.g. motion capture, GRF, foot switch and EMG) has already been synchronised together before the experiment was carried out. In that case,
Do we still need to take EMD into consideration? If yes, what value is suitable for lower limb muscles EMG recording?
3.2) This question is related to part 1.1 and 3.1 of my questions. Do muscle plots in the dynamicElaborations show the EMG signal that corresponds to the length of stance phase with consideration of 0.2 seconds EMD i.e. window is segmented 0.2 second before initial contact however, the plot only shows stance phase OR do they show the signal from the frame that corresponds to EMD (i.e the length of the plot is 0.2s+stance phase)??
**What I want to exactly understand is if stance phase (compute stance phase), or one gait cycle (manual analysis window) is the aim of the analysis, what would be the best value to be considered for electromechanical delay so the desired window shows the true (actual) EMG behaviour?
Thank you in advance for your response.
Pouyan