Investigation of the Relationship Between Electrical Stimulation Frequency and Muscle Frequency Response Under Submaximal Contractions

Abstract

Neuromuscular electrical stimulation (NMES) is a common tool that is used in clinical and laboratory experiments and can be combined with mechanomyography (MMG) for biofeedback in neuroprostheses. However, it is not clear if the electrical current applied to neuromuscular tissues influences the MMG signal in submaximal contractions. The objective of this study is to investigate whether the electrical stimulation frequency influences the mechanomyographic frequency response of the rectus femoris muscle during submaximal contractions. Thirteen male participants performed three maximal voluntary isometric contractions (MVIC) recorded in isometric conditions to determine the maximal force of knee extensors. This was followed by the application of nine modulated NMES frequencies (20, 25, 30, 35, 40, 45, 50, 75, and 100 Hz) to evoke 5% MVIC. Muscle behavior was monitored by the analysis of MMG signals, which were decomposed into frequency bands by using a Cauchy wavelet transform. For each applied electrical stimulus frequency, the mean MMG spectral/frequency response was estimated for each axis (X, Y, and Z axes) of the MMG sensor with the values of the frequency bands used as weights (weighted mean). Only with respect to the Z (perpendicular) axis of the MMG signal, the stimulus frequency of 20 Hz did not exhibit any difference with the weighted mean (P = 0.666). For the frequencies of 20 and 25 Hz, the MMG signal displayed the bands between 12 and 16 Hz in the three axes (P < 0.050). In the frequencies from 30 to 100 Hz, the muscle presented a higher concentration of the MMG signal between the 22 and 29 Hz bands for the X and Z axes, and between 16 and 34 Hz bands for the Y axis (P < 0.050 for all cases). We observed that MMG signals are not dependent on the applied NMES frequency, because their frequency contents tend to mainly remain between the 20- and 25-Hz bands. Hence, NMES does not interfere with the use of MMG in neuroprosthesis.

Assessment of muscle activity using electrical stimulation and mechanomyography: a systematic review

“…The literature also demonstrates that the NMES frequency does not correlate with the MMG frequency response. Papcke et al [ 32 ] reported that during NMES at 5% maximum voluntary isometric contraction, the application of a 20-, 25-, 30-, 35-, 40-, 45-, 50-, 75-, and 100-Hz stimulation frequency did not correlate with any of the three axes analyzed during the Cauchy wavelet-based frequency analysis of MMG signals from the RF. Specifically, the mechanical characteristics of the RF have exhibited a frequency of 20–25 Hz that differs from and is not governed by the stimulation frequency.…”

“…Because MMG provides useful information on the musculoskeletal system, various MMG features, such as the onset time, recovery time, and relaxation time, should be examined after PAP [ 36 , 37 ]. In contrast, no correlation was found between the frequency of stimulation and the MMG response [ 32 ]. Based on this perspective, the reliability of muscle recruitment and mechanical features remains an issue that should be addressed in future studies.…”

Application of facial neuromuscular electrical stimulation (fNMES) in psychophysiological research: Practical recommendations based on a systematic review of the literature

“…Low frequencies (< 20 Hz) should be avoided, as they lead to greater discomfort (Sluka & Walsh, 2003 ) and the pulses can be individually perceived by the participant—low frequencies induce transient tension (twitches). Recently, there has been growing interest in very-high-frequency NMES outside of the face, such as the trunk and limbs of the body, using 100–250 Hz (Doucet & Mettler, 2018 ; Grosprêtre et al, 2017 ; Papcke et al, 2018 ) as well as frequencies in the kilohertz range (Vaz & Frasson, 2018 ), as they may evoke greater central nervous system (CNS) changes by primarily recruiting sensory axons (Mang et al, 2010 ). To date, there is no consensus on the best frequency for fNMES, with studies using 25 Hz (Pilurzi et al, 2013 , 2020 ), 60 Hz (Zariffa et al, 2014 ), and up to 250 Hz (Ilves et al, 2019 ); see Table 1 .…”

Application of facial Neuromuscular Electrical Stimulation (fNMES) in psychophysiological research – practical recommendations based on a systematic review of the literature

“…Low frequencies (< 20 Hz) should be avoided, as they lead to greater discomfort (Sluka & Walsh, 2003) and the pulses can be individually perceived by the participantlow frequencies induce transient tension (twitches). Recently, there has been growing interest in high-frequency NMES using 100 -250 Hz (Doucet & Mettler, 2018;Grosprêtre et al, 2017;Papcke et al, 2018) as well as frequencies in the kilo-Hertz range (Vaz & Frasson, 2018), as they may evoke greater CNS changes by primarily recruiting sensory axons (Mang et al, 2010). To date, there is no consensus on the best frequency for fNMES, with studies using 25 Hz (Pilurzi et al, 2013(Pilurzi et al, , 2020, 60 Hz (Zariffa et al, 2014), and up to 250 Hz (Ilves et al, 2019), see Table 1.…”