Pattern Classification Techniques for EMG Signal Decomposition

EMG Signal Decomposition Using Motor Unit Potential Train Validity

“…The length of the window applied to the signal for selecting MUPs can be variable [54], [55], [59], [65], [69][70][71], or it can be fixed [1], [7], [19], [26], [45], [49], [50], [53], [54], [58], [66], [67], [72], [74][75][76][77][78][79][80][81][82]. If a variable-length window is chosen for analysis, the length of the window is adjusted based on the duration of the MUPs, for which the beginning and end of the MUPs are detected by thresholding.…”

“…A MUP begins when its sample values exceed a threshold and ends when they fall below this threshold [54], [55], [59], [70], [71]. If a fixed-length window is chosen for analysis, the length of the window is set to include a fixed duration, typically 2.5 ms [1], [7], [19], [26], [27], [72], [74], [76][77][78], [81][82][83] or 6 ms [58], [66], [67]. Longer windows improve MUP representation, but will increase decomposition time.…”

“…Raw-data (time samples) and first-or second -derivative of time samples [1], [5][6][7], [19], [25], [27], [72], [74], [76][77][78][79][80], [82], [86], [87], power spectrum and Fourier transform coefficients [45], [49], [50], [62], wavelet coefficients [53][54][55], [59], [59], [79], [81], [83], [88][89][90][91][92][93][94], and principal components of wavelet coefficients [95] are features that have been used to represent and assign MUPs to MUPTs. Using power spectrum coefficients [62] or wavelet coefficients of MUPs decreases the dimensionality of the feature space and hence may improve the processing time.…”

“…Several existing decomposition procedures are based solely on clustering [53], [58], [65][66][67], [69], [74], [91], [93], [94], [108][109][110][111]. However, generally, a clustering technique is followed by supervised classification [1], [2], [7], [19], [27], [54], [55], [62], [72], [73], [76][77][78][79][80], [80][81][82], [86][87][88][89], [112], [113] and both clustering and supervised classification tasks are repeated across a number of iterations. Throughout multiple iterations, the detected MUPs are assigned to the corresponding MUPTs until either the extracted MUPTs are stable or some termination criteria are met.…”

“…NMJ jitter is the variability in the time required at the neuromuscular junctions of a MU to depolarize its muscle fiber membranes [1], [19], [114], [115]. MU firing pattern information can be used to test the validity of assignments made using MUP shape only, (i.e., passively) [19], [45], [49], [50], [58], [65], [74], [75], or it can be used together with shape information to measure the certainty in assigning a MUP to a MUPT (i.e., actively) [1], [2], [5][6][7], [19], [25][26][27], [68], [72], [76][77][78][79], [81], [82]. However, one should consider that MU firing pattern information may not be valid in all cases.…”