Twitch Analysis as an Approach to Motor Unit Activation During Electrical Stimulation

1994 ◽  
Vol 19 (4) ◽  
pp. 451-461 ◽  
Author(s):  
Marc Heyters ◽  
Alain Carpentier ◽  
Jacques Duchateau ◽  
Karl Hainaut
Keyword(s):  
Electrical Stimulation ◽  
Human Subjects ◽  
Motor Nerve ◽  
Motor Units ◽  
Electrical Stimulus ◽  
Equal Proportion ◽  
Motor Point ◽  
Time To Peak ◽  
Slow Type ◽  
The Relationship

The mechanical twitch in response to increasing electrical stimulus intensity, delivered both over the motor point and motor nerve, was recorded in the first dorsal interosseous (FDI) and the adductor pollicis (AP), and only over the motor point in the soleus (Sol), lateral (LG), and medial (MG) gastrocnemius muscles of human subjects. The relationship between intensity of electrical stimulation (ES) and twitch torque showed a positive linear regression in all muscles. In the FDI and AP the relationship was not significantly different when ES was applied at the motor point or over the motor nerve. At small intensities of activation, ES induced larger twitch torques in the MG and LG, which contain a roughly equal proportion of slow and fast motor units (MUs) compared to the Sol, which is composed mainly of slow type fibres. Moreover, the relationship between ES intensity and twitch time-to-peak is best fitted in all muscles by a power curve that shows a greater twitch time-to-peak range in its initial part for muscles containing a larger proportion of fast MUs (LG, MG) than for muscles mainly composed of slow MUs (Sol). In conclusion, these results induced by ES at the motor point and/or over the motor nerve confirm the concept of a reversed sequence of MU activation, as compared to voluntary contractions, and document this viewpoint in muscles of different function and composition. The reversed sequence of MU activation is more clearly evident during motor point ES. Key words: muscle contraction, mechanical twitch, motor point, nerve

Relationship Between Simulated Common Synaptic Input and Discharge Synchrony in Cat Spinal Motoneurons

2001 ◽  
Vol 86 (5) ◽  
pp. 2266-2275 ◽  
Author(s):  
Marc D. Binder ◽  
Randall K. Powers
Keyword(s):  
Synaptic Input ◽  
Human Subjects ◽  
Motor Units ◽  
Human Hand ◽  
Spinal Motoneurons ◽  
Common Input ◽  
Voluntary Contractions ◽  
High Degree ◽  
The Relationship ◽  
Repetitive Discharge

Synchronized discharge of individual motor units is commonly observed in the muscles of human subjects performing voluntary contractions. The amount of this synchronization is thought to reflect the extent to which motoneurons in the same and related pools share common synaptic input. However, the relationship between the proportion of shared synaptic input and the strength of synchronization has never been measured directly. In this study, we simulated common shared synaptic input to cat spinal motoneurons by driving their discharge with noisy, injected current waveforms. Each motoneuron was stimulated with a number of different injected current waveforms, and a given pair of waveforms were either completely different or else shared a variable percentage of common elements. Cross-correlation histograms were then compiled between the discharge of motoneurons stimulated with noise waveforms with variable degrees of similarity. The strength of synchronization increased with the amount of simulated “common” input in a nonlinear fashion. Moreover, even when motoneurons had >90% of their simulated synaptic inputs in common, only ∼25–45% of their spikes were synchronized. We used a simple neuron model to explore how variations in neuron properties during repetitive discharge may lead to the low levels of synchronization we observed experimentally. We found that small variations in spike threshold and firing rate during repetitive discharge lead to large decreases in synchrony, particularly when neurons have a high degree of common input. Our results may aid in the interpretation of studies of motor unit synchrony in human hand muscles during voluntary contractions.

scholarly journals Brain Stem Potentials Evoked by Electrical Stimulation of the Cochlea in Human Subjects

1979 ◽  
Vol 88 (4) ◽  
pp. 550-556 ◽  
Author(s):  
Arnold Starr ◽  
Derald E. Brackmann
Keyword(s):  
Electrical Stimulation ◽  
Brain Stem ◽  
Human Subjects ◽  
Electrical Stimulus ◽  
Scalp Electrode ◽  
Square Wave ◽  
Implanted Electrodes ◽  
Stimulus Parameters ◽  
Stimulation Of

Brain stem potentials were recorded from scalp electrode to biphasic square wave electrical stimulation of implanted electrodes in the cochlea of three patients. Reliable potentials could be recorded that appeared 1.5 to 2.0 msec prior to the customary acoustically-evoked brain stem potentials. The effects of variations in electrical stimulus parameters of rate and intensity were measured. Brain stem potentials can provide objective indices of the effectiveness of electrical stimulation of the cochlea in man.

scholarly journals Bioengineered model of the human motor unit with physiologically functional neuromuscular junctions

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Rowan P. Rimington ◽  
Jacob W. Fleming ◽  
Andrew J. Capel ◽  
Patrick C. Wheeler ◽  
Mark P. Lewis
Keyword(s):  
Neuromuscular Junction ◽  
Motor Neuron ◽  
Motor Unit ◽  
Motor Nerve ◽  
Motor Units ◽  
Extracellular Matrices ◽  
Synaptic Membrane ◽  
Type I ◽  
Dependent Manner ◽  
Human Motor

AbstractInvestigations of the human neuromuscular junction (NMJ) have predominately utilised experimental animals, model organisms, or monolayer cell cultures that fail to represent the physiological complexity of the synapse. Consequently, there remains a paucity of data regarding the development of the human NMJ and a lack of systems that enable investigation of the motor unit. This work addresses this need, providing the methodologies to bioengineer 3D models of the human motor unit. Spheroid culture of iPSC derived motor neuron progenitors augmented the transcription of OLIG2, ISLET1 and SMI32 motor neuron mRNAs ~ 400, ~ 150 and ~ 200-fold respectively compared to monolayer equivalents. Axon projections of adhered spheroids exceeded 1000 μm in monolayer, with transcription of SMI32 and VACHT mRNAs further enhanced by addition to 3D extracellular matrices in a type I collagen concentration dependent manner. Bioengineered skeletal muscles produced functional tetanic and twitch profiles, demonstrated increased acetylcholine receptor (AChR) clustering and transcription of MUSK and LRP4 mRNAs, indicating enhanced organisation of the post-synaptic membrane. The number of motor neuron spheroids, or motor pool, required to functionally innervate 3D muscle tissues was then determined, generating functional human NMJs that evidence pre- and post-synaptic membrane and motor nerve axon co-localisation. Spontaneous firing was significantly elevated in 3D motor units, confirmed to be driven by the motor nerve via antagonistic inhibition of the AChR. Functional analysis outlined decreased time to peak twitch and half relaxation times, indicating enhanced physiology of excitation contraction coupling in innervated motor units. Our findings provide the methods to maximise the maturity of both iPSC motor neurons and primary human skeletal muscle, utilising cell type specific extracellular matrices and developmental timelines to bioengineer the human motor unit for the study of neuromuscular junction physiology.

scholarly journals Modulation of torque evoked by wide-pulse, high-frequency neuromuscular electrical stimulation and the potential implications for rehabilitation and training

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Chris Donnelly ◽  
Jonathan Stegmüller ◽  
Anthony J. Blazevich ◽  
Fabienne Crettaz von Roten ◽  
Bengt Kayser ◽  
...  
Keyword(s):  
Electrical Stimulation ◽  
High Frequency ◽  
Neuromuscular Electrical Stimulation ◽  
Motor Units ◽  
Progressive Increase ◽  
Great Promise ◽  
Measured Parameter ◽  
Time Integral ◽  
Spinal Circuitry ◽  
Evoked Force

AbstractThe effectiveness of neuromuscular electrical stimulation (NMES) for rehabilitation is proportional to the evoked torque. The progressive increase in torque (extra torque) that may develop in response to low intensity wide-pulse high-frequency (WPHF) NMES holds great promise for rehabilitation as it overcomes the main limitation of NMES, namely discomfort. WPHF NMES extra torque is thought to result from reflexively recruited motor units at the spinal level. However, whether WPHF NMES evoked force can be modulated is unknown. Therefore, we examined the effect of two interventions known to change the state of spinal circuitry in opposite ways on evoked torque and motor unit recruitment by WPHF NMES. The interventions were high-frequency transcutaneous electrical nerve stimulation (TENS) and anodal transcutaneous spinal direct current stimulation (tsDCS). We show that TENS performed before a bout of WPHF NMES results in lower evoked torque (median change in torque time-integral: − 56%) indicating that WPHF NMES-evoked torque might be modulated. In contrast, the anodal tsDCS protocol used had no effect on any measured parameter. Our results demonstrate that WPHF NMES extra torque can be modulated and although the TENS intervention blunted extra torque production, the finding that central contribution to WPHF NMES-evoked torques can be modulated opens new avenues for designing interventions to enhance WPHF NMES.

scholarly journals Investigation of different stimulation patterns with doublet pulses to reduce muscle fatigue

2019 ◽  
Vol 6 ◽  
pp. 205566831982580 ◽  
Author(s):  
Ruslinda Ruslee ◽  
Jennifer Miller ◽  
Henrik Gollee
Keyword(s):  
Electrical Stimulation ◽  
Muscle Fatigue ◽  
Functional Electrical Stimulation ◽  
Muscle Activation ◽  
Motor Units ◽  
Pulse Interval ◽  
Time Interval ◽  
Fatigue Index ◽  
Significant Difference ◽  
Cord Injury

Introduction: Functional electrical stimulation is a common technique used in the rehabilitation of individuals with a spinal cord injury to produce functional movement of paralysed muscles. However, it is often associated with rapid muscle fatigue which limits its applications. Methods: The objective of this study is to investigate the effects on the onset of fatigue of different multi-electrode patterns of stimulation via multiple pairs of electrodes using doublet pulses: Synchronous stimulation is compared to asynchronous stimulation patterns which are activated sequentially (AsynS) or randomly (AsynR), mimicking voluntary muscle activation by targeting different motor units. We investigated these three different approaches by applying stimulation to the gastrocnemius muscle repeatedly for 10 min (300 ms stimulation followed by 700 ms of no-stimulation) with 40 Hz effective frequency for all protocols and doublet pulses with an inter-pulse-interval of 6 ms. Eleven able-bodied volunteers (28 ± 3 years old) participated in this study. Ultrasound videos were recorded during stimulation to allow evaluation of changes in muscle morphology. The main fatigue indicators we focused on were the normalised fatigue index, fatigue time interval and pre-post twitch–tetanus ratio. Results: The results demonstrate that asynchronous stimulation with doublet pulses gives a higher normalised fatigue index (0.80 ± 0.08 and 0.87 ± 0.08) for AsynS and AsynR, respectively, than synchronous stimulation (0.62 ± 0.06). Furthermore, a longer fatigue time interval for AsynS (302.2 ± 230.9 s) and AsynR (384.4 ± 279.0 s) compared to synchronous stimulation (68.0 ± 30.5 s) indicates that fatigue occurs later during asynchronous stimulation; however, this was only found to be statistically significant for one of two methods used to calculate the group mean. Although no significant difference was found in pre-post twitch–tetanus ratio, there was a trend towards these effects. Conclusion: In this study, we proposed an asynchronous stimulation pattern for the application of functional electrical stimulation and investigated its suitability for reducing muscle fatigue compared to previous methods. The results show that asynchronous multi-electrode stimulation patterns with doublet pulses may improve fatigue resistance in functional electrical stimulation applications in some conditions.

scholarly journals Features of the relationship between the parameters of left ventricular mechanics and the level of biomarkers of heart failure in patients with epicardial obesity

2021 ◽  
Vol 28 (Supplement_1) ◽  
Author(s):  
O Gritsenko ◽  
GA Chumakova
Keyword(s):  
Heart Failure ◽  
Diastolic Dysfunction ◽  
Speckle Tracking ◽  
Left Atrial Volume ◽  
Left Ventricular ◽  
Serum Biomarker ◽  
Volume Index ◽  
Time To Peak ◽  
Ventricular Mechanics ◽  
The Relationship

Abstract Funding Acknowledgements Type of funding sources: None. Currently, there is no serum biomarker that is a marker of the presence of heart failure (HF) at an early stage. It is also shown that the traditional indicators used for the diagnosis diastolic dysfunction (DD) of left ventricular (LV) using echocardiography (ECG) are not informative enough. Thus, it is currently relevant to study new serum biomarkers of DD, such as sST2, as well as to study the mechanics of LV. Objective to study the relationship between mechanics of LV and the level of sST2 (bioamarker of HF) in patients with epicardial obesity (EO). Materials and methods The study included 110 men with general obesity. According to the results of echocardiography (ECG), patients were divided into 2 groups: EO (+) with epicardial fat thickness (tEAT) ≥7 mm (n = 70); EO (-) with tEAT <7 mm (n = 40) without diastolic dysfunction according to the results of ECG. All patients were assessed for sST2 and NT-pro-BNP levels using enzyme immunoassay. Using speckle-tracking ECG, the mechanics of LV were studied (twist LV, peak twist ratio LV, time to peak twist of LV, peak untwist ratio LV, time to peak untwist of LV). The exclusion criteria were the presence of coronary pathology, arterial hypertension, and type 2 diabetes mellitus. Results In the group patients with EO ( + ) a statistically significant increase in the level of sST2 was revealed in comparison with the group of EO (-) [21,55 ng/ml (26,52; 15,40) and 9.89 ng/ml (11.12; 7.95); p = 0.001, respectively], while the levels of NT-pro-BNP in both groups were not statistically different [211.36 pg / ml (254.0; 156.0) and 204.81 pg / ml (268.0; 157.0), respectively, p = 0.85]. When determining the parameters of DD LV by ECG, there were no statistical differences between the EO (+) and EO (-) groups [e ", cm / sec 0.09 (0.11; 0.09) and 0.09 (0.11; 0.09), respectively, p = 0.63; E/e " , units, 7.80 (8.90; 6.55) in the EO (+) and 8.53 (9.70; 7.20) in the EO group ( - ), p = 0.08; left atrial volume index, ml / sq2, in the EO group (+) 28.39 (31.25; 24.17) and in the EO group(-) 27,82 (30,21; 25,66), p = 0.55; in the EO group ( + ), the maximum speed of tricuspid regurgitation, m / sec, is 2.78 (2.9; 2.58) in the EO group(-) 2,67 (2,87; 2,41), p = 0.13]. According to the results of speckle-tracking ECG in the EO (+) group, an increase peak untwist ratio LV to -128.31 (-142.0; -118.0) deg/s-1 (p = 0.002) and an increase time to peak untwist of LV of 476.44 (510.0; 411.0) msec was determined in comparison with the EO ( - ) group (p = 0.03). A significant relationship between peak untwist ratio LV and sST2 was revealed (r = 0.37; p = 0.02). Conclusion Thus, it can be assumed that patients with EO have DD LV at the preclinical stage, which is not diagnosed using traditional ECG indicators. The serum biomarker sST2 is an early marker of the presence of HF.

5 Examination of the relationship between changes in workload and changes in loaded countermovement jump during a rugby union season

2021 ◽  
Vol 55 (16) ◽  
pp. 941.3-942
Author(s):  
Rob Strong ◽  
Daniel West ◽  
Joe Kupsarevic
Keyword(s):  
Peak Power ◽  
Rank Order ◽  
Rugby Union ◽  
Countermovement Jump ◽  
Match Play ◽  
Time To Peak ◽  
Significant Relationships ◽  
Flight Season ◽  
Acute Changes ◽  
The Relationship

BackgroundThe loaded countermovement jump (CMJ) is a variation on the normal CMJ (bodyweight-only), used routinely in sport settings as a measure of neuromuscular fatigue (NMF). Although commonplace, the CMJ variables that are most sensitive to NMF remain somewhat unclear.PurposeThe aim of this study was to examine the relationship between changes in workload and changes in the loaded CMJ; specifically, to determine its suitability for assessment of NMF.MethodsEighteen professional rugby union players performed loaded CMJ tests on seven occasions over the course of thirteen weeks, during an English top-flight season. Eight CMJ variables were measured, assessing different aspects of the CMJ. Workload was measured by GPS total distance and was the sum of the previous week’s data, recorded in on-field training and match-play. Spearman’s rank-order correlations were calculated to identify the relationship between changes in workload and changes in loaded CMJ variables.ResultsNo significant relationships were found between loaded CMJ variables and workload with no lag or workload lagged one week. Significant relationships were found between workload lagged 2 weeks and flight time/contact time (FT-CT; rs=-0.35; p=0.04) and time to peak power (TtPP; rs=0.35; p=0.05).ConclusionThis study suggests loaded CMJ is not a suitable test to monitor acute changes to NMF. However, results also indicate that FT-CT and TtPP, are associated with changes in workload lagged 2-weeks. Therefore, certain CMJ variables may prove useful to help prescribe alterations to athlete training plans following periods of heavy workload.

The Behaviour and Neuromuscular System of Gonactinia Prolifera, A Swimming Sea-Anemone

1971 ◽  
Vol 55 (3) ◽  
pp. 611-640
Author(s):  
ELAINE A. ROBSON
Keyword(s):  
Electrical Stimulation ◽  
Mechanical Stimulation ◽  
Motor Units ◽  
Nerve Cells ◽  
Sea Anemone ◽  
Neuromuscular System ◽  
Sea Anemones ◽  
Nerve Net ◽  
Local Contraction ◽  
Electric Shocks

1. In Gonactinia well-developed ectodermal muscle and nerve-net extend over the column and crown and play an important part in the anemone's behaviour. 2. Common sequences of behaviour are described. Feeding is a series of reflex contractions of different muscles by means of which plankton is caught and swallowed. Walking, in the form of brief looping steps, differs markedly in that it continues after interruptions. Anemones also swim with rapid tentacle strokes after contact with certain nudibranch molluscs, strong mechanical disturbance or electrical stimulation. 3. Swimming is attributed to temporary excitation of a diffuse ectodermal pacemaker possibly situated in the upper column. 4. From the results of electrical and mechanical stimulation it is concluded that the endodermal neuromuscular system resembles that of other anemones but that the properties of the ectodermal neuromuscular system require a new explanation. The size and spread of responses to electric shocks vary with intensity, latency is variable and there is a tendency to after-discharge. There is precise radial localization, for example touching a tentacle or the column causes it to bend towards or away from the stimulus. 5. A model to explain these and other features includes multipolar nerve cells closely linked to the nerve-net which would act as intermediate motor units, causing local contraction of the ectodermal muscle. This scheme can be applied to other swimming anemones but there is no evidence that it holds for sea anemones generally.

Sign in / Sign up

Export Citation Format

Share Document