Abstract
Problem StatementIn mechanomyography (MMG), crosstalk refers to the contamination of the signal from the muscle of interest by the signal from another muscle or muscle group that is in close proximity.PurposeThe aim of the present study was two-fold: i) to quantify the level of crosstalk in the mechanomyographic (MMG) signals from the longitudinal (Lo), lateral (La) and transverse (Tr) axes of the extensor digitorum (ED), extensor carpi ulnaris (ECU) and flexor carpi ulnaris (FCU) muscles during isometric wrist flexion (WF) and extension (WE), radial (RD) and ulnar (UD) deviations; and ii) to analyze whether the three-directional MMG signals influence the level of crosstalk between the muscle groups during these wrist postures.MethodsTwenty, healthy right-handed men (mean ± SD: age = 26.7±3.83 y; height = 174.47±6.3 cm; mass = 72.79±14.36 kg) participated in this study. During each wrist posture, the MMG signals propagated through the axes of the muscles were detected using three separate tri-axial accelerometers. The x-axis, y-axis, and z-axis of the sensor were placed in the Lo, La, and Tr directions with respect to muscle fibers. The peak cross-correlations were used to quantify the proportion of crosstalk between the different muscle groups.ResultsThe average level of crosstalk in the MMG signals generated by the muscle groups ranged from: 34.28–69.69% for the Lo axis, 27.32–52.55% for the La axis and 11.38–25.55% for the Tr axis for all participants and their wrist postures. The Tr axes between the muscle groups showed significantly smaller crosstalk values for all wrist postures [F (2, 38) = 14–63, p<0.05, η 2 = 0.416–0.769].SignificanceThe results may be applied in the field of human movement research, especially for the examination of muscle mechanics during various types of the wrist postures.
Highlights
The mechanomyography (MMG) technique has been employed as an alternative non-invasive tool to surface electromyography recently [1,2], and provides additional information on motor unit recruitment and its firing rate for evaluating the conditions of muscle function [3,4]
Archer et al [16] found that MMG signals mainly propagate along the Lo direction of the muscle fibers if the frequencies are greater than 25 Hz and mainly in the Tr direction if the frequencies are less than 25 Hz
The aim of the present study was twofold: i) to quantify the level of crosstalk in the MMG signals generated by the Lo, La, and Tr axes over the extensor digitorum (ED), extensor carpi ulnaris (ECU), and flexor carpi ulnaris (FCU) muscles during wrist flexion (WF) and extension (WE), as well as radial (RD) and ulnar (UD) deviations, and ii) to analyze whether the three-directional MMG signals alter the level of crosstalk between the muscle groups during all wrist postures
Summary
The mechanomyography (MMG) technique has been employed as an alternative non-invasive tool to surface electromyography (sEMG) recently [1,2], and provides additional information on motor unit recruitment and its firing rate for evaluating the conditions of muscle function [3,4]. The crosstalk that occurs between adjacent muscles is one of the more important concerns associated with both MMG [5,6] and sEMG techniques [7,8]. When measuring the extent of crosstalk between the MMG signals of different muscles, the most interesting issue is the propagation direction of the mechanical waves that form the MMG signal. Cescon et al found that an MMG signal generated by a single motor unit propagates in the transverse (Tr) direction, but not in the longitudinal (Lo) direction, at the location of the sensor with respect to the muscle fibers [14]. Another study found that the MMG signal propagates both the Lo and Tr to the muscle fiber direction [15].
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