Voluntary Muscle Contraction Detection Algorithm Based on LSTM for Muscle Quality Measurement Algorithm

In this paper, we propose the long–short-term memory (LSTM)-based voluntary and non-voluntary (VNV) muscle contraction classification algorithm in an electrical stimulation (ES) environment. In order to measure the muscle quality (MQ), we employ the non-voluntary muscle contraction signal, which occurs by the ES. However, if patient movement, such as voluntary muscle contractionm, occurs during the ES, the electromyography (EMG) sensor captures the VNV muscle contraction signals. In addition, the voluntary muscle contraction signal is a noise component in the MQ measurement technique, which uses only non-voluntary muscle contraction signals. For this reason, we need the VNV muscle contraction classification algorithm to classify the mixed EMG signal. In addition, when recording EMG while using the ES, the EMG signal is significantly contaminated due to the ES signal. Therefore, after we suppress the artifact noise, which is contained in the EMG signal, we perform VNV muscle contraction classification. For this, we first eliminate the artifact noise signal using the ES suppression algorithm. Then, we extract the feature vector, and then the feature vector is reconstructed through the feature selection process. Finally, we design the LSTM-based classification model and compare the proposed algorithm with the conventional method using the EMG data. In addition, to verify the performance of the proposed algorithm, we quantitatively compared results in terms of the confusion matrix and total accuracy. As a result, the performance of the proposed algorithm was higher than that of the conventional methods, including the support vector machine (SVM), artificial neural network (ANN), and deep neural network (DNN).

Cortical silent period

The cortical silent period (cSP) refers to a period of suppression or silencing of ongoing electromyographic (EMG) activity during voluntary muscle contraction induced by a magnetic stimulus over the contralateral primary motor cortex. This chapter summarizes the physiological basis of the cSP, discusses technical aspects and recommendations on how to record and analyze it, and provides an overview of useful clinical applications. Evidence is presented that multiple spinal mechanisms are implicated in the initial part of the cSP, but some may be also active further on, whereas long-lasting cortical inhibitory mechanisms operate throughout the entire cSP, with an emphasis during its later part. The cSP is a highly relevant and clinically useful tool to assess inhibitory corticomotoneuronal mechanisms in health and disease.

Sensory gating and suppression of subjective peripheral sensations during voluntary muscle contraction

Background During voluntary muscle contraction, sensory information induced by electrostimulation of the nerves supplying the contracting muscle is inhibited and the somatosensory evoked potentials (SEPs) amplitude decreases. This depression of sensory input during voluntary muscle contraction has been demonstrated by many studies using electrophysiological methods. However, the association between the electrophysiological response of the sensory system during sustained muscle contraction and subjective peripheral sensation (SPS) is still unclear. The aim of this study was to investigate changes in spinal excitability, SEPs, and SPS during voluntary muscle contraction. Results The appearance rate of the F-wave was significantly higher during muscle contraction than rest, whereas no significant difference was observed in F-wave latency between muscle contraction and rest. Furthermore, the P25 amplitude of SEPs was significantly lower during muscle contraction than rest, whereas the N20 amplitude of SEPs exhibited no significant differences. The SPS was significantly lower during muscle contraction than rest Conclusions We conclude that sensory gating, which is found in the P25 component of SEPs during muscle contraction, is one of the neurophysiological mechanisms underlying the suppression of SPS.

Sensory gating and suppression of subjective peripheral sensations during voluntary muscle contraction

Background: During voluntary muscle contraction, sensory information induced by electrostimulation of the nerves supplying the contracting muscle is inhibited and the somatosensory evoked potentials (SEPs) amplitude decreases. This depression of sensory input during voluntary muscle contraction has been demonstrated by many studies using electrophysiological methods. However, the association between the electrophysiological response of the sensory system during sustained muscle contraction and subjective peripheral sensation (SPS) is still unclear. The aim of this study was to investigate changes in spinal excitability, SEPs, and SPS during voluntary muscle contraction. Results: The appearance rate of the F-wave was significantly higher during muscle contraction than during rest, whereas no significant difference was observed in F-wave latency between muscle contraction and rest. Furthermore, the P25 amplitude of SEPs was significantly lower during muscle contraction than during rest, whereas the N20 amplitude of SEPs exhibited no significant differences. The SPS was significantly lower during muscle contraction than during rest. Conclusions: We conclude that sensory gating, which is found in the P25 component of SEPs during muscle contraction, is one of the neurophysiological mechanisms underlying the suppression of SPS.

Sensory Gating and Suppression of Subjective Peripheral Sensations During Voluntary Muscle Contraction

Background: During voluntary muscle contraction, sensory information induced by electrostimulation of the nerves supplying the contracting muscle is inhibited and the somatosensory evoked potential (SEP) amplitude decreases. This depression of sensory input during voluntary muscle contraction has been demonstrated by many studies using electrophysiological methods. However, the association between the electrophysiological response of the sensory system during exercise and subjective peripheral sensation (SPS) is still unclear. The aim of this study was to investigate changes in spinal excitability, SEP, and SPS during voluntary muscle contraction.Results: The appearance rate of the F-wave was significantly higher during muscle contraction than rest, whereas no significant difference was observed in F-wave latency between muscle contraction and rest. Furthermore, the P25 amplitude of SEP was significantly lower during muscle contraction than rest, whereas the N20 amplitude of SEP exhibited no significant differences. The SPS was significantly lower during muscle contraction than rest.Conclusions: We conclude that sensory gating, which is found in the P25 component of SEP during muscle contraction, is one of the neurophysiological mechanisms underlying the suppression of SPS.

Implication of the ipsilateral motor network in unilateral voluntary muscle contraction: the cross-activation phenomenon

Voluntary force production requires that the brain produces and transmits a motor command to the muscles. It is widely acknowledged that motor commands are executed from the primary motor cortex (M1) located in the contralateral hemisphere. However, involvement of M1 located in the ipsilateral hemisphere during moderate to high levels of unilateral muscle contractions (>30% of the maximum) has been disclosed in recent years. This phenomenon has been termed cross-activation. The activation of the ipsilateral M1 relies on complex inhibitory and excitatory interhemispheric interactions mediated via the corpus callosum and modulated according to the contraction level. The regulatory mechanisms underlying these interhemispheric interactions, especially excitatory ones, remain vague, and contradictions exist in the literature. In addition, very little is known regarding the possibility that other pathways could also mediate the cross-activation. In the present review, we will therefore summarize the concept of cross-activation during unilateral voluntary muscle contraction and explore the associated mechanisms and other nervous system pathways underpinning this response. A broader knowledge of these mechanisms would consequently allow a better comprehension of the motor system as a whole, as distant brain networks working together to produce the motor command.