Abstract
Introduction: Signal analysis involves time and/or frequency domains, and correlations are described in the literature for voluntary contractions. However, there are few studies about those correlations using mechanomyography (MMG) response during functional electrical stimulation (FES) elicited contractions in spinal cord injured subjects. This study aimed to determine the correlation between spectral and temporal MMG features during FES application to healthy (HV) and spinal cord injured volunteers (SCIV). Methods: Twenty volunteers participated in the research divided in two groups: HV (N=10) and SCIV (N=10). The protocol consisted of four FES profiles transcutaneously applied to quadriceps femoris muscle via femoral nerve. Each application produced a sustained knee extension greater than 65o up to 2 min without adjusting FES intensity. The investigation involved the correlation between MMG signal root mean square (RMS) and mean frequency (MF). Results: HV and SCIV indicated that MMGRMS and MMGMF variations were inversely related with -0.12 ≥ r ≥ -0.82. The dispersion between MMGMF and MMGRMS reached 0.50 ≤ r2 ≤ 0.64. Conclusion The increase in MMGRMS and the decrease in MMGMF may be explained by the motor units coherence during fatigue state or by motor neuron adaptation (habituation) along FES application (without modification on parameters).
Highlights
Signal analysis involves time and/or frequency domains, and correlations are described in the literature for voluntary contractions
The stimulator output amplitude was adjusted in 82 ± 16 V for healthy volunteers (HV) and 161 ± 36 V for spinal cord injured volunteers (SCIV)
Our results indicate a negative correlation between the analyzed parameters (MMGRMS and MMGMF) to both groups as found by Tarata (2003) with HV during voluntary contraction
Summary
Signal analysis involves time and/or frequency domains, and correlations are described in the literature for voluntary contractions. There are few studies about those correlations using mechanomyography (MMG) response during functional electrical stimulation (FES) elicited contractions in spinal cord injured subjects. Mechanomyography (MMG) allows the measurement of mechanical oscillations produced by muscle contraction without electromagnetic interference yielded by FES (Krueger et al, 2014). In this sense, MMG signals may be applied in clinical settings (Cè et al, 2015) to control myoelectrical prostheses, orthoses (Prociow et al, 2008) or neuroprostheses (Chen et al, 2016; Popovic and Thrasher, 2004). MMG enables the evaluation of FES‐induced muscle contraction
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