The scaling of motor noise with muscle strength and motor unit number in humans

2004 ◽  
Vol 157 (4) ◽  
pp. 417-430 ◽  
Author(s):  
Antonia F. de C. Hamilton ◽  
Kelvin E. Jones ◽  
Daniel M. Wolpert
Keyword(s):  
Muscle Strength ◽  
Motor Unit ◽  
Motor Noise

scholarly journals Model-Based Analysis of Muscle Strength and EMG-Force Relation with respect to Different Patterns of Motor Unit Loss

2021 ◽  
Vol 2021 ◽  
pp. 1-9
Author(s):  
Chengjun Huang ◽  
Maoqi Chen ◽  
Yingchun Zhang ◽  
Sheng Li ◽  
Ping Zhou
Keyword(s):  
Muscle Strength ◽  
Motor Neuron ◽  
Motor Unit ◽  
Muscle Force ◽  
Motor Units ◽  
Force Variability ◽  
Valuable Insight ◽  
Model Based ◽  
Force Relation ◽  
Pool Model

This study presents a model-based sensitivity analysis of the strength of voluntary muscle contraction with respect to different patterns of motor unit loss. A motor unit pool model was implemented including simulation of a motor neuron pool, muscle force, and surface electromyogram (EMG) signals. Three different patterns of motor unit loss were simulated, including (1) motor unit loss restricted to the largest ones, (2) motor unit loss restricted to the smallest ones, and (3) motor unit loss without size restriction. The model outputs including muscle force amplitude, variability, and the resultant EMG-force relation were quantified under two different motor neuron firing strategies. It was found that motor unit loss restricted to the largest ones had the most dominant impact on muscle strength and significantly changed the EMG-force relation, while loss restricted to the smallest motor units had a pronounced effect on force variability. These findings provide valuable insight toward our understanding of the neurophysiological mechanisms underlying experimental observations of muscle strength, force control, and EMG-force relation in both normal and pathological conditions.

scholarly journals Force variability is mostly not motor noise: Theoretical implications for motor control

2021 ◽  
Vol 17 (3) ◽  
pp. e1008707
Author(s):  
Akira Nagamori ◽  
Christopher M. Laine ◽  
Gerald E. Loeb ◽  
Francisco J. Valero-Cuevas
Keyword(s):  
Motor Unit ◽  
Muscle Force ◽  
Critical Path ◽  
Control Strategies ◽  
Discharge Rate ◽  
Muscle Mechanics ◽  
Sensorimotor Control ◽  
Force Variability ◽  
Motor Noise ◽  
Signal Dependence

Variability in muscle force is a hallmark of healthy and pathological human behavior. Predominant theories of sensorimotor control assume ‘motor noise’ leads to force variability and its ‘signal dependence’ (variability in muscle force whose amplitude increases with intensity of neural drive). Here, we demonstrate that the two proposed mechanisms for motor noise (i.e. the stochastic nature of motor unit discharge and unfused tetanic contraction) cannot account for the majority of force variability nor for its signal dependence. We do so by considering three previously underappreciated but physiologically important features of a population of motor units: 1) fusion of motor unit twitches, 2) coupling among motoneuron discharge rate, cross-bridge dynamics, and muscle mechanics, and 3) a series-elastic element to account for the aponeurosis and tendon. These results argue strongly against the idea that force variability and the resulting kinematic variability are generated primarily by ‘motor noise.’ Rather, they underscore the importance of variability arising from properties of control strategies embodied through distributed sensorimotor systems. As such, our study provides a critical path toward developing theories and models of sensorimotor control that provide a physiologically valid and clinically useful understanding of healthy and pathologic force variability.

scholarly journals Muscle strength and size are associated with motor unit connectivity in aged mice

2018 ◽  
Vol 67 ◽  
pp. 128-136 ◽  
Author(s):  
Kajri A. Sheth ◽  
Chitra C. Iyer ◽  
Christopher G. Wier ◽  
Alexander E. Crum ◽  
Anna Bratasz ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Motor Unit ◽  
Aged Mice

Differences in Mobility Among Older Adults are Associated with Motor Unit Activity and Muscle Strength

2017 ◽  
Vol 49 (5S) ◽  
pp. 1030
Author(s):  
Diba Mani ◽  
Awad M. Almuklass ◽  
Taian Vieira ◽  
Alberto Botter ◽  
Roger M. Enoka
Keyword(s):  
Older Adults ◽  
Muscle Strength ◽  
Motor Unit ◽  
Unit Activity ◽  
Motor Unit Activity

scholarly journals Motor unit recruitment strategies of the vastus lateralis according to sex

2021 ◽  
Author(s):  
Yuxiao Guo ◽  
Eleanor J Jones ◽  
Thomas B Inns ◽  
Isabel A Ely ◽  
Daniel W Stashuk ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Firing Rate ◽  
Motor Unit ◽  
Vastus Lateralis ◽  
Force Production ◽  
Recruitment Strategies ◽  
Linear Regression Models ◽  
Spike Triggered Averaging ◽  
Underrepresentation Of Women ◽  
Intramuscular Electromyography

Despite men exhibiting greater muscle strength than women it remains unclear if there are sex- based differences in muscle recruitment strategies e.g. motor unit (MU) recruitment and modulation of firing rate with increasing force. These differences may explain underrepresentation of women and mixed-sex cohorts in studies of neuromuscular function. Twenty-nine healthy male and thirty-one healthy female participants (18-35 years) were studied. Intramuscular electromyography was used to record individual motor unit potentials (MUPs) and near fibre MUPs from the vastus lateralis (VL) during 10% and 25% maximum isometric voluntary contractions (MVC), and spike-triggered averaging was used to obtain motor unit number estimates (MUNE) of the VL. Multilevel mixed-effects linear regression models were used to investigate the effects of sex and contraction levels. Men exhibited greater muscle strength (p<0.001) and size (p<0.001) than women, with no difference in force steadiness at 10% or 25% MVC. Although women showed higher firing rate (FR) (p=0.014) and FR variability (p=0.044), both sexes showed similar increasing trajectories from low- to mid-level contractions with no sex x contraction level interactions. With increasing contraction level, both men and women exhibited greater MUP size (p<0.001) and neuromuscular junction transmission instability (p<0.001). There were no sex differences in MUNE calculated at 25% MVC. Although some sex-based neuromuscular differences are apparent, similar MU recruitment strategies are employed to increase force production during low to moderate contractions. These findings of notable similarities between sexes support the use of mixed sex cohorts in studies of this nature.

scholarly journals Changes in Motor Unit Activity Associated with Early Recovery of Muscle Strength after Knee Arthroplasty

2010 ◽  
Vol 25 (3) ◽  
pp. 317-321 ◽  
Author(s):  
Eiji YAMADA ◽  
Shin MORITA ◽  
Syouichi TANAKA ◽  
Shigehiro UCHIDA ◽  
Yasuhiro ITOH ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Motor Unit ◽  
Knee Arthroplasty ◽  
Unit Activity ◽  
Early Recovery ◽  
Motor Unit Activity

scholarly journals The Effect of Spinal Manipulation on the Electrophysiological and Metabolic Properties of the Tibialis Anterior Muscle

Healthcare ◽  
2020 ◽  
Vol 8 (4) ◽  
pp. 548
Author(s):  
Imran Khan Niazi ◽  
Ernest Nlandu Kamavuako ◽  
Kelly Holt ◽  
Taha Al Muhammadee Janjua ◽  
Nitika Kumari ◽  
...  
Keyword(s):  
Muscle Strength ◽  
Motor Unit ◽  
Repeated Measures ◽  
Tibialis Anterior ◽  
Spinal Manipulation ◽  
Near Infrared ◽  
Discharge Rate ◽  
Tibialis Anterior Muscle ◽  
Passive Movement ◽  
Metabolic Properties

There is growing evidence showing that spinal manipulation increases muscle strength in healthy individuals as well as in people with some musculoskeletal and neurological disorders. However, the underlying mechanism by which spinal manipulation changes muscle strength is less clear. This study aimed to assess the effects of a single spinal manipulation session on the electrophysiological and metabolic properties of the tibialis anterior (TA) muscle. Maximum voluntary contractions (MVC) of the ankle dorsiflexors, high-density electromyography (HDsEMG), intramuscular EMG, and near-infrared spectroscopy (NIRS) were recorded from the TA muscle in 25 participants with low level recurring spinal dysfunction using a randomized controlled crossover design. The following outcomes: motor unit discharge rate (MUDR), strength (force at MVC), muscle conduction velocity (CV), relative changes in oxy- and deoxyhemoglobin were assessed pre and post a spinal manipulation intervention and passive movement control. Repeated measures ANOVA was used to assess within and between-group differences. Following the spinal manipulation intervention, there was a significant increase in MVC (p = 0.02; avg 18.87 ± 28.35%) and a significant increase in CV in both the isometric steady-state (10% of MVC) contractions (p < 0.01; avg 22.11 ± 11.69%) and during the isometric ramp (10% of MVC) contractions (p < 0.01; avg 4.52 ± 4.58%) compared to the control intervention. There were no other significant findings. The observed TA strength and CV increase, without changes in MUDR, suggests that the strength changes observed following spinal manipulation are, in part, due to increased recruitment of larger, higher threshold motor units. Further research needs to investigate the longer term and potential functional effects of spinal manipulation in various patients who may benefit from improved muscle function and greater motor unit recruitment.

scholarly journals The Relationship between Motor Unit Excitability and Muscle Strength before and after Meniscestomy

2014 ◽  
Vol 29 (6) ◽  
pp. 1033-1038
Author(s):  
Takehiro KURONITA ◽  
Yuma KAMATANI ◽  
Hisanori YUMINAGA
Keyword(s):  
Muscle Strength ◽  
Motor Unit ◽  
Before And After ◽  
The Relationship
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