Tracking electromechanical muscle dynamics using ultrafast ultrasound and high-density EMG

Waasdorp, Rick; Mugge, Winfred; Vos, H. R.; Groot, Janke de; Jong, Nico de; Verweij,; Schouten, AC; Daeichin, Verya

doi:10.1109/ultsym.2019.8925557

Cited by 8 publications

(7 citation statements)

References 8 publications

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“…Similar to the current study, this previous research also revealed that fascicle shortening happens before force/torque is measured (3,34,58). However, the magnitude of these delays is considerably smaller than the ones presented herein, with ~6ms (EMG-FL) and ~12ms (EMGforce) of delay for electrically-induced contractions (34,44) and ~29ms (EMG-FL) and ~50ms…”

Section: Cst Fascicle Length and Torque Delayssupporting

confidence: 84%

“…This assessment is commonly known as the electromechanical delay, and has provided important information about the time required for a muscle to generate force/torque from a passive state. Since this analysis commonly neglects the lag between the generation of a contraction and the transmission of force to the tendon and then transmission to the measuring apparatus (which generates great variability in results ( 59)), more recent studies have aimed to quantify these lags by combining conventional bipolar EMG or HDEMG amplitude and ultrasound (3,58).…”

Section: Cst Fascicle Length and Torque Delaysmentioning

confidence: 99%

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Modulations in motor unit discharge are related to changes in fascicle length during isometric contractions

Martinez‐Valdes

Negro

Botter

et al. 2021

Preprint

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Previous studies assessing relationships between muscle mechanics and neural activity have concurrently assessed changes in fascicle length (FL) and neural activation with electromyography (EMG) approaches with low spatial sampling from different muscle regions. This project aimed to assess changes in FL and motor unit (MU) firing, simultaneously, on the same region of interest, with high-density EMG electrodes transparent to ultrasound (HDEMG-US). EMG signals and ultrasound images were recorded simultaneously from the tibialis anterior of 10 participants, using a silicon matrix of 32 electrodes, while performing sustained-isometric ankle-dorsiflexion contractions, at diverse joint positions (0° and 30° plantar flexion) and torques (20% and 40% of maximum). EMG signals were decomposed into individual MUs and changes in FL were assessed with a fascicle-tracking algorithm. MU firing data was converted into a cumulative spike train (CST) that was cross-correlated with dorsiflexion torque (CST-torque) and FL (CST-FL). On average, 7 (3) MUs were identified across contractions. Cross-correlations showed that CST could explain on average 60% (range: 31-85%) and 71% (range: 0.31-0.88) of the variance in FL and torque, respectively. Cross-correlation lags revealed that the delay between CST-FL (~75ms) was smaller than CST-torque (~150ms, p<0.001). Finally, we could observe that both delays increased by ~20ms at 30° of plantar flexion (p<0.05). This study is the first to demonstrate the feasibility of recording single MU activity with HDEMG-US whilst simultaneously evaluating changes in FL. The findings show a close relationship between dorsiflexion torque, FL and CST, also allowing quantification of the delay between each of these signals.

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Section: Cst Fascicle Length and Torque Delayssupporting

confidence: 84%

Section: Cst Fascicle Length and Torque Delaysmentioning

confidence: 99%

Modulations in motor unit discharge are related to changes in fascicle length during isometric contractions

Martinez‐Valdes

Negro

Botter

et al. 2021

Preprint

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“…On the other hand, the mechanical response of entire muscles can be studied using ultrasound (US) (Botter et al, 2013;Dieterich et al, 2017;Tweedell, Tenan and Haynes, 2019). US has also been used for studying the mechanical response of individual MUs in electrically stimulated contractions (Deffieux et al, 2008;Waasdorp et al, 2019Waasdorp et al, , 2021. Furthermore, some studies have suggested that US can even be used at the muscle unit level (Rohlén et al, 2020;Rohlén, Stålberg and Grönlund, 2020;Carbonaro et al, 2022).…”

Section: Introductionmentioning

confidence: 99%

“…On the other hand, the mechanical response of entire muscles can be studied using ultrasound (US) (Botter et al ., 2013; Dieterich et al ., 2017; Tweedell, Tenan and Haynes, 2019). US has also been used for studying the mechanical response of individual MUs in electrically stimulated contractions (Deffieux et al ., 2008; Waasdorp et al ., 2019, 2021). Furthermore, some studies have suggested that US can even be used at the muscle unit level (Rohlén et al ., 2020; Rohlén, Stålberg and Grönlund, 2020; Carbonaro et al ., 2022).…”

Section: Introductionmentioning

confidence: 99%

Kinematics of individual muscle units in natural contractions measured in vivo using ultrafast ultrasound

Lubel

Sgambato

Barsakcioglu

et al. 2022

Preprint

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The study of human neuromechanical control at the motor unit (MU) level has predominantly focussed on electrical activity and force generation, whilst the link between these, the muscle deformation, has not been widely studied. Here, we describe a methodology utilising ultrafast ultrasound (US), allowing imaging of up to tens of thousands of frames per second, to measure the deformation of the muscular tissue due to individual MU twitches for a population of active MUs during voluntary contractions. We used the spiking activity of MUs decomposed from high-density surface electromyography recordings of the tibialis anterior muscle to guide the analysis of simultaneously recorded ultrafast US. With a novel analysis on the US images we identified, with high spatio-temporal precision, the velocity maps associated with single MU movements. From the individual MU profiles obtained from the velocity maps, the region of movement, the duration of the mechanical twitch, the total and active contraction times, and the activation time were computed. The latter features, the temporal features, showed high repeatability across different force levels. The former feature, the spatial feature, showed high consistency across force levels, however the complicated dynamics of the muscle motion resulted in morphing and translation of these regions. Furthermore, the experimental measures provided the first evidence of muscle unit twisting during voluntary contractions. The proposed approach allows, for the first time, non-invasive recordings of muscle deformation due to individual MU activations during voluntary contractions.Key pointsWe identified the activity of single motor units (MUs) from high-density surface electromyography (HDsEMG) and used this information in combination with ultrafast ultrasound to extract local muscle motion due to the contraction of individual muscle unitsMultiple MUs, including those with fibres overlapping in space, can be simultaneously and individually detected using this techniqueThe proposed method allows us to measure both the spiking activity of motor units and their movement within the muscles concomitantlyThe technique allows for populations of MUs to be tracked and monitored in the electrical and mechanical domains simultaneously and non-invasively during natural contractions, thus achieving a high spatio-temporal resolution in the characterization of MU behaviour

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“…However, the individual MU velocity twitches are very small (approximately 3 mm/s [7]), and the territories of different MUs overlap in space [8], thus a given muscle region will have a complex deformation field [9]. When the fibers contract, they push and pull on each other and nearby tissues, setting up propagating waves within the region [10], [11]. Furthermore, deformation due to connective tissue, bones, and blood vessels is larger than the MU twitches, and structures Despite the complexity of the problem, methods have been proposed to extract neural information from recordings using ultrafast US imaging to detect muscle deformation [12]- [14].…”

Section: Introductionmentioning

confidence: 99%

Accurate Identification of Motoneuron Discharges from Ultrasound Images Across the Full Muscle Cross-Section

Lubel,

Rohlén,

Sgambato

et al. 2023

Preprint

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ObjectiveNon-invasive identification of motoneuron (MN) activity is commonly done using (EMG). However, surface EMG (sEMG) signals detect only superficial sources, at less than approximately 10-mm depth. Intramuscular EMG can detect deep sources, but it is limited to sources within a few mm of the detection site. Conversely, ultrasound (US) images have high spatial resolution across the whole muscle cross-section. The activity of MNs can be extracted from US images due to the movements that MN activation generates in the innervated muscle fibers. Current US-based decomposition methods can accurately identify the location and average twitch induced by MN activity. However, they cannot accurately detect MN discharge times.MethodsHere, we present a method based on the convolutive blind source separation of US images to estimate MN discharge times with high accuracy. The method was validated across 10 participants using concomitant sEMG decomposition as the ground truth.Results140 unique MN spike trains were identified from US images, with a rate of agreement (RoA) with sEMG decomposition of 87.4 ± 10.3 %. Over 50% of these MN spike trains had a RoA greater than 90%. Furthermore, with US, we identified additional MUs well beyond the sEMG detection volume, at up to >30 mm below the skin.ConclusionThe proposed method can identify discharges of MNs innervating muscle fibers in a large range of depths within the muscle from US images.SignificanceThe proposed methodology can non-invasively interface with the outer layers of the central nervous system innervating muscles across the full cross-section.

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Tracking electromechanical muscle dynamics using ultrafast ultrasound and high-density EMG

Cited by 8 publications

References 8 publications

Modulations in motor unit discharge are related to changes in fascicle length during isometric contractions

Modulations in motor unit discharge are related to changes in fascicle length during isometric contractions

Kinematics of individual muscle units in natural contractions measured in vivo using ultrafast ultrasound

Accurate Identification of Motoneuron Discharges from Ultrasound Images Across the Full Muscle Cross-Section

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