Quantitative Response of Healthy Muscle Following the Induction of Capsaicin: An Exploratory Randomized Controlled Trial

Abstract Background: Myofascial pain syndrome (MPS) is a prevalent chronic pain disorder primarily characterized by myofascial trigger points (MTrP). There is limited knowledge on the pathophysiology and mechanisms underlying MTrP and its development. Research has previously demonstrated the identification of MTrPs using ultrasound and vibration sonoelastography, although there is some contradictory evidence regarding if MTrPs present as hyper or hypoechoic regions. Electromyography (EMG) investigations of MTrP have demonstrated that MTrP are usually located proximal to innervation zones where the peak surface EMG signals are obtained from. Central sensitization has been proposed as the primary mechanism underlying MTrP development. Central sensitization is associated with hyperexcitability of neuronal responses to normal or noxious stimuli. There is a need for a study that measures ultrasound image textural changes and motor unit activity responses in the muscle following sensitization. The purpose of this study is to determine whether sensitizing healthy muscle using capsaicin induces a regional change in image texture variables within the specific and surrounding muscles, as well as the motor unit frequency and amplitude changes that accompany them.This is an exploratory trial that aims to provide preliminary evidence on whether central sensitization is a direct cause of taut band and MTrP development. Methods: The study conforms to the Consolidated Standards of Reporting Trials recommendations. Ethical approval will be sought from the University Health Network (UHN) Research Ethics Board. This proposed study is a single centered, factorial, randomized placebo-controlled trial with two independent variables, depth of capsaicin application and dose of capsaicin, for a total of four treatment arms and two control treatment groups. Discussion: This will be the first study that assesses the B-mode ultrasound image texture of induced sensitized muscles, and will provide more evidence on muscle motor unit activity and regional changes of central sensitization. Findings from this study may support one of few hypotheses proposed delineating the involvement of central sensitization in the development of trigger points.

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Quantitative response of healthy muscle following the induction of capsaicin: an exploratory randomized controlled trial

Trials ◽

10.1186/s13063-020-04937-4 ◽

2020 ◽

Vol 21 (1) ◽

Author(s):

Valerie Evans ◽

Michael Behr ◽

Kei Masani ◽

Dinesh Kumbhare

Keyword(s):

Motor Unit ◽

Unit Activity ◽

Central Sensitization ◽

Controlled Trial ◽

Ultrasound Image ◽

Trigger Points ◽

Image Texture ◽

Control Treatment ◽

Myofascial Trigger Points ◽

Motor Unit Activity

Abstract Background Myofascial pain syndrome (MPS) is a prevalent chronic pain disorder primarily characterized by myofascial trigger points (MTrPs). There is limited knowledge on the pathophysiology and mechanisms underlying MTrP and its development. Research has previously demonstrated the identification of MTrPs using ultrasound and vibration sonoelastography, although there is some contradictory evidence regarding if MTrPs present as hyper or hypoechoic regions. Electromyography (EMG) investigations of MTrP have demonstrated that MTrPs are usually located proximal to innervation zones where the peak surface EMG signals are obtained from. Central sensitization has been proposed as the primary mechanism underlying MTrP development. Central sensitization is associated with hyperexcitability of neuronal responses to normal or noxious stimuli. There is a need for a study that measures ultrasound image textural changes and motor unit activity responses in the muscle following sensitization. The purpose of this study is to determine whether sensitizing healthy muscle using capsaicin induces a regional change in image texture variables within the specific and surrounding muscles, as well as the motor unit frequency and amplitude changes that accompany them. This is an exploratory trial that aims to provide preliminary evidence on whether central sensitization is a direct cause of taut band and MTrP development. Methods Ethical approval was obtained from the University Health Network (UHN) Research Ethics Board. This proposed study is a single centered, factorial, randomized placebo-controlled trial with two independent variables, depth of capsaicin application and dose of capsaicin, for a total of six treatment arms and three control treatment groups. Discussion This will be the first study that assesses the B-mode ultrasound image texture of induced sensitized muscles and will provide more evidence on muscle motor unit activity and regional changes of central sensitization. Findings from this study may support one of few hypotheses proposed delineating the involvement of central sensitization in the development of trigger points. Trial registration National Institutes of Health ClinicalTrials.gov NCT03944889. Registered on May 07, 2019

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Quantitative Response of Healthy Muscle Following the Induction of Capsaicin: AnExploratory Randomized Controlled Trial

10.21203/rs.2.11950/v4 ◽

2020 ◽

Author(s):

Valerie Evans ◽

Michael Behr ◽

Kei Masani ◽

Dinesh Kumbhare

Keyword(s):

Motor Unit ◽

Unit Activity ◽

Central Sensitization ◽

Myofascial Pain ◽

Controlled Trial ◽

Ultrasound Image ◽

Image Texture ◽

Control Treatment ◽

Myofascial Trigger Points ◽

Motor Unit Activity

Abstract Background: Myofascial pain syndrome (MPS) is a prevalent chronic pain disorder primarily characterized by myofascial trigger points (MTrP). There is limited knowledge on the pathophysiology and mechanisms underlying MTrP and its development. Research has previously demonstrated the identification of MTrPs using ultrasound and vibrationsonoelastography, although there is some contradictory evidence regarding if MTrPs present as hyper or hypoechoic regions. Electromyography (EMG) investigations of MTrP have demonstrated that MTrP are usually located proximal to innervation zones where the peak surface EMG signals are obtained from. Central sensitization has been proposed as the primary mechanism underlying MTrP development. Central sensitization is associated withhyperexcitability of neuronal responses to normal or noxious stimuli. There is a need for a study that measures ultrasound image textural changes and motor unit activity responses in the muscle following sensitization. The purpose of this study is to determine whether sensitizing healthy muscle using capsaicin induces a regional change in image texture variables within the specific and surrounding muscles, as well as the motor unit frequency and amplitude changes that accompany them. This is an exploratory trial that aims to provide preliminary evidence on whether central sensitization is a direct cause of taut band and MTrP development.Methods: Ethical approval was obtained from the University Health Network (UHN)Research Ethics Board. This proposed study is a single centered, factorial, randomized placebo-controlled trial with two independent variables, depth of capsaicin application and dose of capsaicin, for a total of six treatment arms and three control treatment groups. Discussion: This will be the first study that assesses the B-mode ultrasound image texture of induced sensitized muscles, and will provide more evidence on muscle motor unit activity and regional changes of central sensitization. Findings from this study may support one of few hypotheses proposed delineating the involvement of central sensitization in the development of trigger points.Trial Registration: Name: National Institutes of Health ClinicalTrials.gov. Identifier: NCT03944889 Date of Registration: May 07 2019 URL: https://clinicaltrials.gov/ct2/show/NCT03944889

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Quantitative Response of Healthy Muscle Following the Induction of Capsaicin: An Exploratory Randomized Controlled Trial

10.21203/rs.2.11950/v2 ◽

2020 ◽

Author(s):

Valerie Evans ◽

Michael Behr ◽

Kei Masani ◽

Dinesh Kumbhare

Keyword(s):

Motor Unit ◽

Unit Activity ◽

Central Sensitization ◽

Myofascial Pain ◽

Controlled Trial ◽

Ultrasound Image ◽

Image Texture ◽

Control Treatment ◽

Myofascial Trigger Points ◽

Motor Unit Activity

Abstract Background: Myofascial pain syndrome (MPS) is a prevalent chronic pain disorder primarily characterized by myofascial trigger points (MTrP). There is limited knowledge on the pathophysiology and mechanisms underlying MTrP and its development. Research has previously demonstrated the identification of MTrPs using ultrasound and vibration sonoelastography, although there is some contradictory evidence regarding if MTrPs present as hyper or hypoechoic regions. Electromyography (EMG) investigations of MTrP have demonstrated that MTrP are usually located proximal to innervation zones where the peak surface EMG signals are obtained from. Central sensitization has been proposed as the primary mechanism underlying MTrP development. Central sensitization is associated with hyperexcitability of neuronal responses to normal or noxious stimuli. There is a need for a study that measures ultrasound image textural changes and motor unit activity responses in the muscle following sensitization. The purpose of this study is to determine whether sensitizing healthy muscle using capsaicin induces a regional change in image texture variables within the specific and surrounding muscles, as well as the motor unit frequency and amplitude changes that accompany them. This is an exploratory trial that aims to provide preliminary evidence on whether central sensitization is a direct cause of taut band and MTrP development.Methods: Ethical approval was obtained from the University Health Network (UHN) Research Ethics Board. This proposed study is a single centered, factorial, randomized placebo-controlled trial with two independent variables, depth of capsaicin application and dose of capsaicin, for a total of six treatment arms and three control treatment groups.Discussion: This will be the first study that assesses the B-mode ultrasound image texture of induced sensitized muscles, and will provide more evidence on muscle motor unit activity and regional changes of central sensitization. Findings from this study may support one of few hypotheses proposed delineating the involvement of central sensitization in the development of trigger points.Trial Registration: Name: National Institutes of Health ClinicalTrials.gov. Identifier: NCT03944889 Date of Registration: May 07 2019 URL: https://clinicaltrials.gov/ct2/show/NCT03944889

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Quantitative Response of Healthy Muscle Following the Induction of Capsaicin: An Exploratory Randomized Controlled Trial

10.21203/rs.2.11950/v3 ◽

2020 ◽

Author(s):

Valerie Evans ◽

Michael Behr ◽

Kei Masani ◽

Dinesh Kumbhare

Keyword(s):

Motor Unit ◽

Unit Activity ◽

Central Sensitization ◽

Myofascial Pain ◽

Controlled Trial ◽

Ultrasound Image ◽

Image Texture ◽

Control Treatment ◽

Myofascial Trigger Points ◽

Motor Unit Activity

Abstract Background: Myofascial pain syndrome (MPS) is a prevalent chronic pain disorder primarily characterized by myofascial trigger points (MTrP). There is limited knowledge on the pathophysiology and mechanisms underlying MTrP and its development. Research has previously demonstrated the identification of MTrPs using ultrasound and vibrationsonoelastography, although there is some contradictory evidence regarding if MTrPs present as hyper or hypoechoic regions. Electromyography (EMG) investigations of MTrP have demonstrated that MTrP are usually located proximal to innervation zones where the peak surface EMG signals are obtained from. Central sensitization has been proposed as the primary mechanism underlying MTrP development. Central sensitization is associated withhyperexcitability of neuronal responses to normal or noxious stimuli. There is a need for a study that measures ultrasound image textural changes and motor unit activity responses in the muscle following sensitization. The purpose of this study is to determine whether sensitizing healthy muscle using capsaicin induces a regional change in image texture variables within the specific and surrounding muscles, as well as the motor unit frequency and amplitude changes that accompany them. This is an exploratory trial that aims to provide preliminary evidence on whether central sensitization is a direct cause of taut band and MTrP development.Methods: Ethical approval was obtained from the University Health Network (UHN)Research Ethics Board. This proposed study is a single centered, factorial, randomized placebo-controlled trial with two independent variables, depth of capsaicin application and dose of capsaicin, for a total of six treatment arms and three control treatment groups. Discussion: This will be the first study that assesses the B-mode ultrasound image texture of induced sensitized muscles, and will provide more evidence on muscle motor unit activity and regional changes of central sensitization. Findings from this study may support one of few hypotheses proposed delineating the involvement of central sensitization in the development of trigger points.Trial Registration: Name: National Institutes of Health ClinicalTrials.gov.Identifier: NCT03944889Date of Registration: May 07 2019URL: https://clinicaltrials.gov/ct2/show/NCT03944889

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The role of novel motor unit magnetic resonance imaging to investigate motor unit activity in ageing skeletal muscle

Journal of Cachexia Sarcopenia and Muscle ◽

10.1002/jcsm.12655 ◽

2020 ◽

Author(s):

Matthew G. Birkbeck ◽

Andrew M. Blamire ◽

Roger G. Whittaker ◽

Avan Aihie Sayer ◽

Richard M. Dodds

Keyword(s):

Magnetic Resonance Imaging ◽

Skeletal Muscle ◽

Magnetic Resonance ◽

Motor Unit ◽

Unit Activity ◽

Resonance Imaging ◽

Motor Unit Activity

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Blockade of 5-HT2 receptors suppresses rate of torque development and motor unit discharge rate during rapid contractions

Journal of Neurophysiology ◽

10.1152/jn.00470.2021 ◽

2021 ◽

Author(s):

Benjamin Ian Goodlich ◽

Sean A Horan ◽

Justin J Kavanagh

Keyword(s):

Motor Unit ◽

Unit Activity ◽

Repeated Measures ◽

Discharge Rate ◽

Voluntary Contraction ◽

Unit Discharge ◽

Motor Unit Activity ◽

Rate Of Torque Development ◽

Motor Unit Discharge ◽

Torque Development

Serotonin (5-HT) is a neuromodulator that is critical for regulating the excitability of spinal motoneurons and the generation of muscle torque. However, the role of 5-HT in modulating human motor unit activity during rapid contractions has yet to be assessed. Nine healthy participants (23.7 ± 2.2 yr) ingested 8 mg of the competitive 5-HT2 antagonist cyproheptadine in a double-blinded, placebo-controlled, repeated-measures experiment. Rapid dorsiflexion contractions were performed at 30%, 50% and 70% of maximal voluntary contraction (MVC), where motor unit activity was assessed by high-density surface electromyographic decomposition. A second protocol was performed where a sustained, fatigue-inducing dorsiflexion contraction was completed prior to undertaking the same 30%, 50% and 70% MVC rapid contractions and motor unit analysis. Motor unit discharge rate (p < 0.001) and rate of torque development (RTD; p = 0.019) for the unfatigued muscle were both significantly lower for the cyproheptadine condition. Following the fatigue inducing contraction, cyproheptadine reduced motor unit discharge rate (p < 0.001) and RTD (p = 0.024), where the effects of cyproheptadine on motor unit discharge rate and RTD increased with increasing contraction intensity. Overall, these results support the viewpoint that serotonergic effects in the central nervous system occur fast enough to regulate motor unit discharge rate during rapid powerful contractions.

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