Muscle Fiber Conduction Velocity Research Articles

Is fatigue a muscular phenomenon in Parkinson's disease? Implications for rehabilitation.

Fatigue in Parkinson's disease (PD) compromises patients' physical activity and poses questions on how to plan correct rehabilitation training. In addition, the relationship between subjective perceived fatigue and fatigue in motor performance is not yet entirely understood. Therefore, a conclusive interpretation of muscular mechanisms of fatigue in PD has not yet been achieved. Among the various instrumental evaluations for fatigue, multichannel surface electromyography (sEMG) is a recognized tool that permits the study of myoelectric manifestations of fatigue. The aim of this study was to assess if muscles in PD show a different myoelectric fatigue pattern compared to the muscles of healthy age-matched subjects. The design was observational controlled study. Idiopathic Parkinson's Disease, Hohen &Yahr II and III stage, Parkinsonian Fatigue Scale average score ≥2.95, no therapy modification in the 4 weeks preceding the study; exclusion criteria: mini mental state examination ≤24, upper limb disease/symptoms that might interfere with sEMG analysis, presence of other fatigue-related conditions. Twenty patients were selected according to these criteria. Twenty untrained healthy subjects were matched. All subjects underwent a muscle fatigue protocol and a sEMG analysis of the right biceps brachii muscle during electrically stimulated and voluntary contractions in order to obtain a myoelectric fatigue muscular pattern. The myoelectric pattern is characterized by the modifications of the following sEMG variables: reduction of mean frequency and muscle fiber conduction velocity, increase of average rectified value. No statistical differences were observed between groups for sEMG variables and muscular electric behavior in all contraction conditions (all P>0.05). Our results show that parkinsonian muscles do not differ from the muscles of healthy age-matched subjects in developing peripheral myoelectric fatigue. Nevertheless, the role of fatigue perception at rest and particularly during physical activity must be clearly understood in order to further target the rehabilitative approach for fatigued parkinsonian patients and to reduce hypomobility. In rehabilitative terms, these findings allow us to highlight the possibility of performing sustained training with isometric contractions in PD subjects; therefore, fatigue "per se" does not constitute a barrier for the execution of muscular exercises, likewise intensive.

Muscle fibre conduction velocity varies in opposite directions after short- vs. long-duration muscle contractions.

The effects of muscle contractions on muscle fibre conduction velocity have normally been investigated for contractions of a given duration and intensity, with most studies being focused on the decline on conduction velocity during/after prolonged contractions. Herein, we perform a systematic analysis of the changes in conduction velocity after voluntary contractions of different durations and intensities. Conduction velocity was estimated in the vastus lateralis before and after knee extensor isometric maximal voluntary contractions (MVCs) of 1, 3, 6, 10, 30 and 60s, and after brief (3s) contractions at 10, 30, 50, 70, and 90% of MVC force. Measurements were made during the 10-min period following each contraction. (1) Conduction velocity was increased immediately after (1s) the MVCs of brief (≤ 10s) duration (12 ± 2%, P < 0.05), and then returned rapidly (within 15s) to control levels; (2) the extent of the increase in conduction velocity was similar after the 3-s, 6-s, and 10-s MVCs (P > 0.05); (3) the magnitude of the increase in conduction velocity after a brief contraction augmented with the intensity of the contraction (increases of 4.6, 7.7, 11.4, 14.8, and 15.2% for contractions at 10, 30, 50, 70, and 90% of MVC force, respectively); (4) conduction velocity was not decreased immediately after the 30-s MVC (P > 0.05); and (5) conduction velocity did not reach its minimum 1s after the long (≥ 30s) MVCs. Brief (≤ 10s) muscle contractions induce a short-term increase in conduction velocity, lasting 15s, while long (≥ 30s) contractions produce a long-term decrease in conduction velocity, lasting more than 2min.

Chronic fatigue syndrome: Abnormally fast muscle fiber conduction in the membranes of motor units at low static force load

ObjectiveChronic fatigue syndrome (CFS) and fibromyalgia (FM) are disorders of unknown etiology and unclear pathophysiology, with overlapping symptoms of – especially muscular –fatigue and pain. Studies have shown increased muscle fiber conduction velocity (CV) in the non-painful muscles of FM patients. We investigated whether CFS patients also show CV abnormalities. MethodsFemales with CFS (n = 25), with FM (n = 22), and healthy controls (n = 21) underwent surface electromyography of the biceps brachii, loaded up to 20% of maximum strength, during short static contractions. The mean CV and motor unit potential (MUP) velocities with their statistical distribution were measured. ResultsThe CV changes with force differed between CFS-group and both FM-group and controls (P = 0.01). The CV of the CFS-group increased excessively with force (P < 0.001), whereas that of the controls increased only slightly and non-significantly, and that of the FM-group did not increase at all. In the CFS-group, the number of MUPs conveying very high conduction velocities increased abundantly with force and the MUPs narrowed. ConclusionOur results suggest disturbed muscle membrane function in CFS patients, in their motor units involved in low force generation. Central neural deregulation may contribute to this disturbance. SignificanceThese findings help to detangle the underlying mechanisms of CFS.

Electrodiagnostic study in patients with fibromyalgia: Implication for central sensitization

Background: Fibromyalgia is a syndrome characterized by chronic pain, depression, fatigue, and sleep disturbance. Different hypotheses have emerged about its pathogenesis, but central sensitization, which plays an important role in the development of neuropathic pain, is considered to be the main mechanism. We aim to compare patients with fibromyalgia and healthy controls with different electrodiagnostic testing, and if present, to corroborate whether there is any relationship between electrodiagnostic measures. Also, we sought to test the diagnostic value of some of these measures. Methods: A case-control study of thirty-one patients with fibromyalgia with a duration of illness ranging from 5 months to 10 years were recruited for the study. Full medical history, clinical neurological examination, and electrodiagnostic tests of the upper and lower extremity including nerve conduction studies, needle electromyography, sympathetic skin response, cutaneous silent period and muscle fiber conduction velocity. Results: Sympathetic skin response latency and cutaneous silent period latency were not different between the patients and the control group. Cutaneous silent period duration was prolonged and the muscle fiber conduction velocity is faster in the subjects with fibromyalgia. The latter measures have similar diagnostic value. Sex has no significant impact on electrodiagnostic measures and the latter not correlated with patients' age. Conclusion: A central sensitization and concomitant deregulation of the efferent higher motor centers might be implicated in the pathogenic mechanism of fibromyalgia.

Increased resistance towards fatigability in patients with facioscapulohumeral muscular dystrophy

PurposeIn facioscapulohumeral muscular dystrophy (FSHD) fatigue is a major complaint. We aimed to investigate whether during isometric sustained elbow flexions, performance fatigability indexes differ in patients with FSHD with respect to healthy controls.MethodsSeventeen patients with FSHD and seventeen healthy controls performed two isometric flexions of the dominant biceps brachii at 20% of their maximal voluntary contraction (MVC) for 2 min and then at 60% MVC until exhaustion. Muscle weakness was characterized as a percentage of predicted values. Maximal voluntary strength, endurance time and performance fatigability indices (mean frequency of the power spectrum (MNF), muscle fiber conduction velocity (CV) and fractal dimension (FD)), extracted from the surface electromyogram signal (sEMG) were compared between the two groups.ResultsIn patients with FSHD, maximal voluntary strength was 68.7% of predicted value (p < 0.01). Compared to healthy controls, FSHD patients showed reduced MVC (p < 0.001; r = 0.62) and lower levels of performance fatigability, characterized by reduced rate of changes in MNF (p < 0.01; r = 0.56), CV (p < 0.05; 0.37) and FD (p < 0.001; r = 0.51) and increased endurance time (p < 0.001; r = 0.63), during the isometric contraction at 60% MVC.ConclusionA decreased reduction in the slopes of all the considered sEMG parameters during sustained isometric elbow flexions suggests that patients with FSHD experience lower levels of performance fatigability compared to healthy controls.

利用者の温冷感による咬筋部筋電位計測の動作信頼性

With a rise in the number of people requiring nursing-care in the aging society, the demand for welfare equipments that maintain the quality of nursing-care is increasing. In particular, electric wheelchairs are effective in improving QOL because they support the voluntary movement of users, but the majority of them needs to be operated by movements of upper limbs. Then, the authors developed an operation system of electric wheelchairs that is controlled by voluntary head movements. However, EMG measurement system malfunctioned in low temperature environments, which made it impossible to operate electric wheelchairs. Thus, it is necessary to clarify the cause of this malfunction and ensure the stability of operation. In this study, first, the operation was tested in comfortable environments and low temperature environments (-2<PMV<-3). Next, operation reliability was evaluated based on task success rate and malfunction rate. Consequently, the task success rate and the malfunction rate in low temperature environments were 79% and 12%, which were similar to the results in comfortable environments. Therefore, this system can maintain operation reliability at -2<PMV<-3. Meanwhile, it is indispensable to verify in harsher low temperature than -2<PMV<-3 environments, due to be suggested that the change in muscle fiber conduction velocity was small.

Identification of muscle innervation zones using linear electrode arrays: a fundamental step to measure fibers conduction velocity

Fiber conduction velocity (CV) is a parameter correlated to the physiological membrane properties of the skeletal muscle fibers. Changes in muscle fiber CV are correlated to the gradation of force and fatigue, and can be measured by means of surface electromyography EMG (sEMG). sEMG measurement of CV during muscle contractions requires the correct identification of the skeletal muscle innervation zone (IZ). In superficial muscles, IZ location can be detected using linear electrode arrays and visually identified as the point of inversion of the detected motor unit action potential (MUAP) propagation. In the present work, we present a method for the effective and fast detection of the IZ location, through the following procedures: (1) identification of the target superficial muscle considering the muscle fiber architecture; (2) electrode array selection based on interelectrode distance and number of electrodes; (3) subject training to perform submaximal isometric contractions of the target muscle/s; (4) electrode array positioning along the muscle surface to investigate the IZ position during the contractions by visual identification of MUAP patterns.

Design, implementation, and estimation of MFCV for 4-different position of human body using FPGA

The motivation behind this article is to demonstrate the precision and dependability of a Field Programmable Gate Array-based implementation of muscle fibre conduction velocity (MFCV) in customary unique constrictions. The framework, leveraging the DSP unit, acquires the bio signals from four different positions of the human body, including Radial Nerve, Ulnar nerve, Auxiliary Nerve, Median nerve. The information derived through Surface Electromyogram (EMG) Electrodes is depicted as a dynamic bitstreams of the signal. The latest bitstreams are subjected to an algorithm. The subjection corresponds to the correlation of the signals from similar muscle nerves, obtained through the EMG electrodes. The whole calculation framework completely works progressively on the Altera Cyclone-V FPGA. This method is better than finding the signal dependence using a silicon resonator due to its cost and tedious design of the sensors. The myoelectric (Electromyographic) signal is recorded by the electrodes set on the four different locations associated with 1550 unique contractions. The in-vivo estimations illustrate that below the equivalent trial states, in 10 test days, the framework uncovers an MFCV mean estimation of 6.60 (±) 0.42 m/s for Median nerve Position, 6.43 (±) 0.33 m/s for Ulnar Nerve Position, 6.54 (±) 0.41 m/s for Radial nerve Position and 7.21 (±) 0.49 m/s for Auxiliary Nerve Position. The values evidence decent dependability of the estimations in an eternal application. The core part of the device being MFCV estimation, upon empirical evaluations with clinical values, shows an accuracy of 97%.

RETRACTED ARTICLE: FPGA based peripheral myopathy monitoring using MFCV at dynamic contractions

This article describes the design of a wearable, remote inserted framework for the Peripheral Myopathy (PM) estimation in customary dynamic movements. This unique circumstance, the electromyographic investigation can give data about the muscle and nerve condition by evaluating the connected MFCV. The framework works with synchronized and digitized information tests from four electromyographic channels, which are situated on both hands of the individual test, misusing the rules given by an inserted positional filtering calculation. This work displays a novel approach for the assessment of MFCV that relies upon the excellent anode relative estimation standard. The system uses dynamic bitstream change of Electromyographic signs and low computational retort for utilization of bit stream cross-correlation. The structure totally chips away at Cyclone-V altera field programmable gate array. The test outcomes on five subjects (Human Beings) show the limit of the proposed procedure for planning the physiological muscle fibre conduction velocity values, as nitty–gritty in a therapeutic composition. In explicit, differentiating the remedial characteristics, obtained in controlled conditions, with the system evacuated muscle fibre conduction velocity, the proportionate preliminary conditions: preeminent bungle is, overall, 0.3 m/s. The framework restores a likelihood of invalid constant measures underneath of 2% (assuming the worst possible scenario).

Muscle fiber conduction velocity in the vastus lateralis and medialis muscles of soccer players after ACL reconstruction.

The neural factors underlying the persistency of quadriceps weakness after anterior cruciate ligament reconstruction (ACLR) have been only partially explained. This study examined muscle fiber conduction velocity (MFCV) as an indirect parameter of motor unit recruitment strategies in the vastus lateralis (VL) and medialis (VM) muscles of soccer players with ACLR. High-density surface electromyography (HDsEMG) was acquired from VL and VM in nine soccer players (22.7±2.9years; BMI: 22.08±1.72kg·m-2 ; 7.7±2.2months post-surgery). Voluntary muscle force and the relative myoelectrical activity from the reconstructed and contralateral sides were recorded during linearly increasing isometric knee extension contractions up to 70% of maximal voluntary isometric force (MVIF). The relation of MFCV and force was examined by linear regression analysis at the individual subject level. The initial (intercept), peak (MFCV70 ), and rate of change (slope) of MFCV related to force were compared between limbs and muscles. The MVIF was lower in the reconstructed side than in the contralateral side (-%20.5; P<.05). MFCV intercept was similar among limbs and muscles (P>.05). MFCV70 and MFCV slope were lower in the reconstructed side compared to the contralateral for both VL (-28.5% and -10.1%, respectively; P<.001) and VM (-22.6% and -8.1%, respectively; P<.001). The slope of MFCV was lower in the VL than VM, but only in the reconstructed side (-12.4%; P<.001). These results suggest possible impairments in recruitment strategies of high-threshold motor units (HTMUs) as well as deficits in sarcolemmal excitability, fiber diameter, and discharge rate of knee extensor muscles following ACLR.

Reproducibility of muscle fibre conduction velocity during linearly increasing force contractions

Muscle fibre conduction velocity (MFCV) is a basic physiological parameter biophysically related to the diameter of muscle fibres and properties of the sarcolemma. The aim of this study was to assess the intersession reproducibility of the relation between voluntary force and estimates of average muscle fibre conduction velocity (MFCV) from multichannel high-density surface electromyographic recordings (HDsEMG). Ten healthy men performed six linearly increasing isometric ankle dorsiflexions on two separate experimental sessions, 4 weeks apart. Each session involved the recordings of voluntary force during maximal isometric (MViF) and submaximal ramp contractions at 35–50–70% of MViF. Concurrently, the HDsEMG activity was detected from the tibialis anterior muscle and MFCV estimates were derived in 250-ms epochs. Absolute and relative reproducibility of MFCV initial value (intercept) and rate of change (regression slope) as a function of force were assessed by within-subject coefficient of correlation (CVw) and with intraclass correlation coefficient (ICC). MFCV was positively correlated with voluntary force (R2 = 0.75 ± 0.12) in all individuals and test conditions (P < 0.001). Average CVw for MFCV intercept and slope were of 2.6 ± 2.0% and 11.9 ± 3.2% and ICC values of 0.96 and 0.94, respectively.Overall, MFCV regression coefficients showed a high degree of intersession reproducibility in both absolute and relative terms. These results may have important practical implications in the tracking of training-induced neuromuscular changes and/or in the monitoring of the progress of neuromuscular disorders when a full sEMG signal decomposition is problematic or not possible.

Conduction Velocity of Muscle Action Potential of Knee Extensor Muscle During Evoked and Voluntary Contractions After Exhaustive Leg Pedaling Exercise.

PurposeMuscle fiber conduction velocity (CV) has been developed to estimate neuromuscular fatigue and measured during voluntary (VC) and electrically evoked (EC) contractions. Since CV during VC and EC reflect different physiological phenomena, the two parameters would show inconsistent changes under the conditions of neuromuscular fatigue. We investigated the time-course changes of CV during EC and VC after fatiguing exercise.MethodsIn 14 young males, maximal voluntary contraction (MVC) of knee extensor muscles, CV during electrical stimulation (CV-EC) and MVC (CV-VC) were measured before and immediately, 30 min, 60 min, 120 min, and 24 h after exhaustive leg pedaling exercise.ResultsCV-EC significantly increased immediately after the fatiguing exercise (p < 0.05) and had a significant negative correlation with MVC in merged data from all time-periods (r = −0.511, p < 0.001). CV-VC significantly decreased 30, 60, and 120 min after the fatiguing exercise (p < 0.05) and did not show any correlations with MVC (p > 0.05).ConclusionThese results suggest that CV during EC and VC exhibits different time-course changes, and that CV during EC may be appropriate to estimate the degree of neuromuscular fatigue after fatiguing pedaling exercise.

Age related changes in surface myoelectric signals

The initial values and the time course of muscle fiber conduction velocity and of surface myoelectric signal spectral variables were studied during voluntary or electrically elicited contractions of the tibialis anterior muscle of 15 healthy elderly human subjects. Age ranged from 65 to 84 years. Isometric voluntary contractions were performed at 20% MVC (Maximal Voluntary Contraction) and 80% MVC for 20 s. Tetanic electrical stimulation was then applied to the main muscle motor point for 20 s with surface electrodes. Two stimulation rates (20 Hz and 40 Hz) and two stimulation amplitudes were used to induce different degrees of fatigue. One stimulation amplitude was supramaximal, the second was adjusted to induce a response (M-wave) about 30% of the maximal. Results were compared with those reported in previous work on healthy adults (age range 18 to 43 years). The main findings of this work are: (a) when voluntary contraction level is increased from 20% MVC to 80% MVC conduction velocity and spectral variables increase; this increase is significantly smaller in elderly subjects, (b) during sustained contractions at 80% MVC the decrease of conduction velocity and spectral variables is significantly smaller in elderly subjects, (c) during contractions induced by supramaximal stimulation at 40 Hz the decrease of conduction velocity and spectral variables is not significantly different in the two age groups. It is concluded that points a and b reflect the age related decrease of number and size of fast twitch fibers indicated by histological data. Point c is discussed and possible explanations are suggested.

Comparative Study on Muscle Function, Temperature on Muscle Surface and Muscle Fiber Conduction Velocity by Static and Dynamic Stretching

Comparative Study on Muscle Function, Temperature on Muscle Surface and Muscle Fiber Conduction Velocity by Static and Dynamic Stretching

Upper and lower limb performance fatigability in people with multiple sclerosis investigated through surface electromyography: a pilot study

Objective: Fatigue experienced by people with multiple sclerosis (pwMS) is multidimensional, consisting of different components, such as perceived, physical and cognitive fatigue and performance fatigability. At present, there is no gold standard to assess performance fatigability in pwMS; therefore, we aimed to determine whether, during a fatiguing task, average rectified value (ARV), mean frequency of the power spectrum (MNF), muscle fiber conduction velocity (CV) and fractal dimension (FD) of surface electromyography (sEMG) may be used as indirect indices of performance fatigability. Moreover, we analyzed whether a three-week rehabilitation program impacts on performance fatigability in pwMS, and whether a relationship between sEMG parameters and trait levels of perceived fatigability, before and after rehabilitation, does exist. Approach: Twenty-one pwMS performed a 20% maximal voluntary contraction (MVC) of 1 min, and afterwards a 60% MVC held until exhaustion. sEMG signals were detected from the biceps brachii, vastus medialis and vastus lateralis. Performance fatigability was determined at entry to (t0) and discharge from (t1) rehabilitation. Perceived fatigability was measured at t0 and t2, one month after rehabilitation. Main results: ARV, MNF, CV and FD rates of change showed significant changes at t0 and t1 (p < 0.05) during the high-level contraction in the BB, but rather limited in the vastii muscles. Moreover, rehabilitation did not induce any reductions in either perceived or performance fatigability. No significant correlations between ARV, MNF, CV and FD rates of change during the 60% MVC and perceived fatigability, at t0 and t2, were found. Significance: Our findings suggest that the sEMG parameters are useful for indirectly assessing performance fatigability in pwMS during sub-maximal fatiguing contractions, particularly in the biceps brachii.

High-density electromyographic assessment of stretch reflex activity during drop jumps from varying drop heights

This study investigated how drop heights and their associated drop jump performance relate to stretch reflex modulations. Eleven male subjects performed ten drop jumps from each of three individually predetermined drop heights. These were the drop height resulting in maximal performance (OPT), as well as 10 cm below (LOW) and above (HIGH) maximal performance. To quantify drop jump performance the reactive strength index, derived from force plate measures, was used. High-density surface EMG provided both stretch reflex response timing and size, as well as novel insight into the associated motor unit recruitment via muscle fiber conduction velocity estimations. These measures were examined in the vastus lateralis (VL), soleus (SOL) and gastrocnemius medialis (GM).Drop jump performance improved by 9% (p < 0.001) from LOW to OPT and decreased by 5% (p = 0.008) from OPT to HIGH. Despite decreasing performance, stretch reflex responses were largest at HIGH. Stretch reflex responses timing did not change; staying within the short (SOL, <60 ms) and medium (VL, GM; 60–85 ms) latency response time-frames. Motor unit recruitment appeared to change across drop heights only for VL, whereas activation intensity only changed for SOL. These results indicate that during drop jumps above OPT neuromuscular modifications result in VL no longer being maximally recruited.

Visceral Manipulation Decreases Pain, Increases Cervical Mobility and Electromyographic Activity of the Upper Trapezius Muscle in Non-Specific Neck Pain Subjects with Functional Dyspepsia: Two Case Reports

The lack of clear knowledge about the etiology of nonspecific neck pain (NS-NP) strengthens the need for other mechanisms, still poorly described in the literature, to be investigated. Therefore, a quantitative analysis of two cases of NS-NP in subjects with functiona dyspepsia was conducted in order to verify the immediate and seven-day postintervention effects of visceral manipulation (VM) to the stomach and liver on neck pain, cervical range of motion (ROM), and electromyographic (EMG) activity of the upper trapezius muscle. Case A was an 18-year-old female with a complaint of nonspecific neck pain for one year, with reported pain on waking, momentary intermittent pain, and occasional symptoms of paresthesia in the upper limbs. Case B was a 25-year-old female with a complaint of cervical pain for one year, accompanied by pain in the unilateral temporomandibular joint, and medial thoracic region. Both cases presented functional dyspepsia. The results demonstrated (subjects A and B, respectively) a general increase in cervical ROM (range: 12.5% to 44.44%) and amplitude of the EMG signal (immediately postintervention: 57.62 and 20.78; post seven days: 53.54% and 18.83%), and an increase in muscle fiber conduction velocity immediately postintervention (4.44% and 7.44%) and a decrease seven days postintervention (25.25% and 21.18%). For pain, a decrease was observed immediately postintervention (23.07% and 76.92%) and seven days postintervention (100% for both subjects). A single VM provided important clinical improvement in neck pain, cervical spine range of motion, and EMG activity of the upper trapezius muscle, immediately and seven days postintervention in two NS-NP subjects with functional dyspepsia.

Separation of interference surface electromyogram into propagating and non-propagating components

A new algorithm is introduced to decompose interference surface electromyogram (EMG) recorded by a multi-channel system aligned to muscle fibers into propagating and non-propagating contributions. Muscle fiber conduction velocity (CV) is also estimated, reducing the bias induced by non-propagating components. The algorithm is fast and stable, as it is based on alignment and averaging procedures. Simulated signals (with different fat thickness, SNR, number of channels, epoch duration and force level) are used to test the algorithm. The median cross-correlation of simulated and estimated components were about 98% and 90%, for propagating and non-propagating terms, respectively. CV was estimated better than using a multi-channel maximum likelihood approach applied to double differential data (mean error of 0.08 versus 0.13 m/s), with a greater gain in case of thinner fat layer, low SNR and few channels. Example applications to experimental data are also shown (single motor unit action potential, M-wave and interference EMG).Propagating components reflect the travelling of action potentials along muscle fibers. Preliminary tests show that non-propagating contributions provide selective information on motor units firing statistics. The separation of interference EMG into propagating and non-propagating components opens new perspectives, e.g., in the study of synergies, common drive and myoelectric manifestations of fatigue.

The Effects of Quercetin Supplementation on Eccentric Exercise-Induced Muscle Damage.

The aim of the present investigation was to test the hypothesis that quercetin (Q) may prevent the strength loss and neuromuscular impairment associated with eccentric exercise-induced muscle damage (EEIMD). Twelve young men (26.1 ± 3.1 years) ingested either Q (1000 mg/day) or placebo (PLA) for 14 days using a randomized, double-blind, crossover study design. Participants completed a comprehensive neuromuscular (NM) evaluation before, during and after an eccentric protocol able to induce a severe muscle damage (10 sets of 10 maximal lengthening contractions). The NM evaluation comprised maximal voluntary isometric contraction (MVIC) and force–velocity relationship assessments with simultaneous recording of electromyographic signals (EMG) from the elbow flexor muscles. Soreness, resting arm angle, arm circumference, plasma creatine kinase (CK) and lactate dehydrogenase (LDH) were also assessed. Q supplementation significantly increased the isometric strength recorded during MVIC compared to baseline (+4.7%, p < 0.05). Moreover, the torque and muscle fiber conduction velocity (MFCV) decay recorded during the eccentric exercise was significant lower in Q compared to PLA. Immediately after the EEIMD, isometric strength, the force–velocity relationship and MFCV were significantly lower when participants were given PLA rather than Q. Fourteen days of Q supplementation seems able to attenuate the severity of muscle weakness caused by eccentric-induced myofibrillar disruption and sarcolemmal action potential propagation impairment.

Decoding motor neuron activity from epimysial thin-film electrode recordings following targeted muscle reinnervation

Objective. Surface electromyography (EMG) is currently used as a control signal for active prostheses in amputees who underwent targeted muscle reinnervation (TMR) surgery. Recent research has shown that it is possible to access the spiking activity of spinal motor neurons from multi-channel surface EMG. In this study, we propose the use of multi-channel epimysial EMG electrodes as an interface for decoding motor neurons activity following TMR. Approach. We tested multi-channel epimysial electrodes (48 detection sites) built with thin-film technology in an animal model of TMR. Eight animals were tested 12 weeks after reinnervation of the biceps brachii lateral head by the ulnar nerve. We identified the position of the innervation zone and the muscle fiber conduction velocity of motor units decoded from the multi-channel epimysial recordings. Moreover, we characterized the pick-up volume by the distribution of the motor unit action potential amplitude over the epimysium surface. Main results. The electrodes provided high quality signals with average signal-to-noise ratio >30 dB across 95 identified motor units. The motor unit action potential amplitude decreased with increasing distance of the electrode from the muscle fibers (P 0.001). The decrease was more pronounced for bipolar compared to monopolar derivations. The average muscle fiber conduction velocity was 2.46 ± 0.83 m s−1. Most of the neuromuscular junctions were close to the region where the nerve was neurotized, as observed from the EMG recordings and imaging data. Significance. These results show that epimysial electrodes can be used for selective recordings of motor unit activities with a pick-up volume that included the entire muscle in the rat hindlimb. Epimysial electrodes can thus be used for detecting motor unit activity in muscles with specific fascicular territories associated to different functions following TMR surgery.