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https://www.readbyqxmd.com/read/27101290/loss-of-knee-extensor-torque-complexity-during-fatiguing-isometric-muscle-contractions-occurs-exclusively-above-the-critical-torque
#1
Jamie Pethick, Samantha L Winter, Mark Burnley
The complexity of knee extensor torque time series decreases during fatiguing isometric muscle contractions. We hypothesized that because of peripheral fatigue, this loss of torque complexity would occur exclusively during contractions above the critical torque (CT). Nine healthy participants performed isometric knee extension exercise (6 s of contraction, 4 s of rest) on six occasions for 30 min or to task failure, whichever occurred sooner. Four trials were performed above CT (trials S1-S4, S1 being the lowest intensity), and two were performed below CT (at 50% and 90% of CT)...
June 1, 2016: American Journal of Physiology. Regulatory, Integrative and Comparative Physiology
https://www.readbyqxmd.com/read/26560202/surface-hydrogenation-regulated-wrinkling-and-torque-capability-of-hydrogenated-graphene-annulus-under-circular-shearing
#2
Yinfeng Li, Silin Liu, Dibakar Datta, Zhonghua Li
Wrinkles as intrinsic topological feature have been expected to affect the electrical and mechanical properties of atomically thin graphene. Molecular dynamics simulations are adopted to investigate the wrinkling characteristics in hydrogenated graphene annulus under circular shearing at the inner edge. The amplitude of wrinkles induced by in-plane rotation around the inner edge is sensitive to hydrogenation, and increases quadratically with hydrogen coverage. The effect of hydrogenation on mechanical properties is investigated by calculating the torque capability of annular graphene with varying hydrogen coverage and inner radius...
2015: Scientific Reports
https://www.readbyqxmd.com/read/22556396/distinct-profiles-of-neuromuscular-fatigue-during-muscle-contractions-below-and-above-the-critical-torque-in-humans
#3
Mark Burnley, Anni Vanhatalo, Andrew M Jones
Whether the transition in fatigue processes between "low-intensity" and "high-intensity" contractions occurs gradually, as the torque requirements are increased, or whether this transition occurs more suddenly at some identifiable "threshold", is not known. We hypothesized that the critical torque (CT; the asymptote of the torque-duration relationship) would demarcate distinct profiles of central and peripheral fatigue during intermittent isometric quadriceps contractions (3-s contraction, 2-s rest). Nine healthy men performed seven experimental trials to task failure or for up to 60 min, with maximal voluntary contractions (MVCs) performed at the end of each minute...
July 2012: Journal of Applied Physiology
https://www.readbyqxmd.com/read/22246220/knee-extensor-fatigue-threshold-is-related-to-whole-body-vo2max
#4
Cornelis J de Ruiter, Ellen A Maas, Mariska G H Wesseling, Arnold de Haan
PURPOSE: Above a given exercise intensity, rapid muscle fatigue will occur. We explored the possibility of assessing torque threshold for peripheral fatigue during single-legged repetitive isometric knee extensor exercise. We hypothesized this fatigue threshold to be related to the general aerobic fitness level and the so-called "critical torque" (CT) established with a recently validated 5-min all-out test. METHODS: Seventeen healthy men (VO(2max) = 44.7-69.6 mL·kg(-1)·min(-1)) performed six submaximal (20%-55% maximal voluntary contraction [MVC]) 5-min bouts of 60 repetitive contractions (3-s on, 2-s off)...
July 2012: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/20637234/comparing-electromyographic-and-mechanomyographic-frequency-based-fatigue-thresholds-to-critical-torque-during-isometric-forearm-flexion
#5
COMPARATIVE STUDY
C Russell Hendrix, Terry J Housh, Clayton L Camic, Jorge M Zuniga, Glen O Johnson, Richard J Schmidt
UNLABELLED: Theoretically, the critical torque (CT), electromyographic mean power frequency fatigue threshold (EMG MPF(FT)), and mechanomyographic mean power frequency fatigue threshold (MMG MPF(FT)) describe the maximal non-fatiguing isometric torque level. PURPOSE: The purposes of this study were threefold: (1) to determine if the mathematical model for estimating the EMG MPF(FT) during isometric muscle actions of the leg extensors was applicable to isometric muscle actions of the forearm flexors; (2) to determine if the mathematical model for estimating the EMG MPF(FT) from the frequency of the EMG signal was applicable to the frequency domain of the MMG signal to estimate a new fatigue threshold called the mechanomyographic mean power frequency fatigue threshold (MMG MPF(FT)); and (3) to compare the mean torque levels derived from the CT, EMG MPF(FT), and MMG MPF(FT) tests during isometric forearm flexion muscle actions...
December 15, 2010: Journal of Neuroscience Methods
https://www.readbyqxmd.com/read/19947704/critical-casimir-interaction-of-ellipsoidal-colloids-with-a-planar-wall
#6
S Kondrat, L Harnau, S Dietrich
Based on renormalization group concepts and explicit mean field calculations, we study the universal contribution to the effective force and torque acting on an ellipsoidal colloidal particle, which is dissolved in a critical fluid and is close to a homogeneous planar substrate. At the same closest distance between the substrate and the surface of the particle, the ellipsoidal particle prefers an orientation parallel to the substrate, and the magnitude of the fluctuation-induced force is larger than if the orientation of the particle is perpendicular to the substrate...
November 28, 2009: Journal of Chemical Physics
https://www.readbyqxmd.com/read/19915500/critical-torque-estimated-time-to-exhaustion-and-anaerobic-work-capacity-from-linear-and-nonlinear-mathematical-models
#7
C Russell Hendrix, Terry J Housh, Michelle Mielke, Jorge M Zuniga, Clayton L Camic, Glen O Johnson, Richard J Schmidt
UNLABELLED: Theoretically, critical torque (CT) is the maximal isometric torque that can be maintained without fatigue, and anaerobic work capacity (AWC) is the total "isometric work" associated with stored energy sources within the muscle. PURPOSE: The purpose of this study was twofold: 1) to determine whether there were differences among the estimates of CT and AWC from linear and nonlinear mathematical models and 2) to compare the estimated time to exhaustion (ETTE) values associated with the CT estimates from the linear and nonlinear mathematical models...
December 2009: Medicine and Science in Sports and Exercise
https://www.readbyqxmd.com/read/19394361/a-new-emg-frequency-based-fatigue-threshold-test
#8
C Russell Hendrix, Terry J Housh, Glen O Johnson, Michelle Mielke, Clayton L Camic, Jorge M Zuniga, Richard J Schmidt
UNLABELLED: Theoretically, the critical torque (CT) and electromyographic mean power frequency fatigue threshold (EMG MPF(FT)) describe the maximal non-fatiguing isometric torque level. PURPOSE: The purposes of this study were two-fold: (1) to determine if the mathematical model for estimating the EMG fatigue threshold (EMG(FT)) from the amplitude of the EMG signal was applicable to the frequency domain of the EMG signal to estimate a new fatigue threshold called the EMG MPF(FT); and (2) to compare the torque level derived from the CT test to that of the EMG MPF(FT) test for the vastus lateralis (VL) muscle during isometric muscle actions of the leg extensors...
June 30, 2009: Journal of Neuroscience Methods
https://www.readbyqxmd.com/read/19150854/estimation-of-critical-torque-using-intermittent-isometric-maximal-voluntary-contractions-of-the-quadriceps-in-humans
#9
Mark Burnley
To determine whether the asymptote of the torque-duration relationship (critical torque) could be estimated from the torque measured at the end of a series of maximal voluntary contractions (MVCs) of the quadriceps, eight healthy men performed eight laboratory tests. Following familiarization, subjects performed two tests in which they were required to perform 60 isometric MVCs over a period of 5 min (3 s contraction, 2 s rest), and five tests involving intermittent isometric contractions at approximately 35-60% MVC, each performed to task failure...
March 2009: Journal of Applied Physiology
https://www.readbyqxmd.com/read/19139939/a-semiflexible-polymer-ring-acting-as-a-nano-propeller
#10
H Wada
The dynamics of a rotating elastic nano-ring driven in a viscous fluid by an externally applied torque about a specific axis is studied using elasto-hydrodynamic simulations. We show that a helical deformation of the ring filament is excited, and that this leads to directed propulsion which is independent of the direction of rotation. It is found that the propulsive force and efficiency initially increase as the torque is increased, and then decrease discontinuously at a buckling transition at a critical torque...
January 2009: European Physical Journal. E, Soft Matter
https://www.readbyqxmd.com/read/18352599/shape-transition-and-propulsive-force-of-an-elastic-rod-rotating-in-a-viscous-fluid
#11
Bian Qian, Thomas R Powers, Kenneth S Breuer
The deformation of an elastic rod rotating in a viscous fluid is considered, with applications related to flagellar motility. The rod is tilted relative to the rotation axis, and experiments and theory are used to study the shape transition when driven either at constant torque or at constant speed. At low applied torque, the rod bends gently and generates small propulsive force. At a critical torque, the rotation speed increases abruptly, and the rod forms a helical shape with increased propulsive force. We find good agreement between theory and experiment...
February 22, 2008: Physical Review Letters
https://www.readbyqxmd.com/read/16606051/propulsion-with-a-rotating-elastic-nanorod
#12
Manoel Manghi, Xaver Schlagberger, Roland R Netz
The dynamics of a rotating elastic filament is investigated using Stokesian simulations. The filament, straight and tilted with respect to its rotation axis for small driving torques, undergoes at a critical torque a strongly discontinuous shape bifurcation to a helical state. It induces a substantial forward propulsion whatever the sense of rotation: a nanomechanical force-rectification device is established.
February 17, 2006: Physical Review Letters
https://www.readbyqxmd.com/read/11736212/removal-of-dna-bound-proteins-by-dna-twisting
#13
A Sarkar, J F Marko
We present a simple model of how local torsional stress in DNA can eject a DNA-bound protein. An estimate of the torque tau(*) required to eject a typical DNA-bound protein is made through a two-state model of the equilibrium between the bound and unbound states of the protein. For the familiar case of a nucleosome octamer bound to double-stranded DNA, we find this critical torque to be approximately equal to 9k(B)T. More weakly bound proteins and large (approximately equal to kilobase) loops of DNA are shown to be destabilized by smaller torques of only a few k(B)T...
December 2001: Physical Review. E, Statistical, Nonlinear, and Soft Matter Physics
https://www.readbyqxmd.com/read/11558056/-pulley-system-isokinetic-training-in-knee-rehabilitation-initial-results
#14
M Thomas, C Kubaile, M Busse
AIM: The purpose of this study was to evaluate the results of a knee rehabilitation program after knee surgery, based on an isokinetic pulley System (Moflex, Recotec/Bernina, Switzerland). METHOD: In this prospective study, 73 patients participated in a standardized rehabilitation program (ACL reconstruction, ACL/all: n = ;51; patellar tendon, ACL/P: n = 30; semitendinosus tendon, ACL/S: n = 21; arthroscopic meniscus resection: n = 22). The major aspect of the program was an isokinetic pulley system with an implemented, linearly working knee device...
July 2001: Zeitschrift Für Orthopädie und Ihre Grenzgebiete
https://www.readbyqxmd.com/read/11253528/-rope-pulley-isokinetic-system-in-shoulder-rehabilitation-initial-results
#15
M Thomas, J Grünert, S Standtke, M W Busse
AIM: Of this study was to evaluate the results of a shoulder rehabilitation program of different shoulder diseases, based on an isokinetie pulley system ("Moflex", Recotec/Bernina, Swiss). METHOD: In this prospective study 70 patients participated in a standardized rehabilitation program (instability: n = 19; rotator cuff disorders: n = 23; impingement syndrome without lesion: n = 16; others: n = 12; operative therapy: n = 47). The major aspect of the program was an isokinetic pulley system...
January 2001: Zeitschrift Für Orthopädie und Ihre Grenzgebiete
https://www.readbyqxmd.com/read/6481624/resonance-at-the-wrist-demonstrated-by-the-use-of-a-torque-motor-an-instrumental-analysis-of-muscle-tone-in-man
#16
M Lakie, E G Walsh, G W Wright
The resonance of the relaxed wrist for flexion-extension movements in the horizontal plane has been investigated by using rhythmic torques generated by a printed motor. In the normal subject the resonant frequency of the wrist is ca. 2 Hz unless the torque is reduced below a certain critical value when the system is no longer linear and the resonant frequency rises. This critical torque level, and the damping are both less in women than men. The resonant frequency is uninfluenced by surgical anaesthesia. With added bias the increase of resonant frequency at low torques still occurs although the hand is now oscillating about a displaced mean position...
August 1984: Journal of Physiology
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