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Geoffrey A Power - One of the best experts on this subject based on the ideXlab platform.

  • perception of effort during an isometric contraction is influenced by prior muscle lengthening or shortening
    European Journal of Applied Physiology, 2021
    Co-Authors: Benjamin Kozlowski, Benjamin Pageaux, Emma F Hubbard, Benjamin St Peters, Philip J Millar, Geoffrey A Power
    Abstract:

    Following a shortening or lengthening muscle contraction, Torque produced in the isometric steady state is lower (Residual Torque depression; rTD) or higher (Residual Torque enhancement; rTE), respectively, compared to a purely isometric contraction at the same final muscle length and level of activation. This is referred to as the history dependence of force. When matching a given Torque level, there is greater muscle activation (electromyography; EMG) following shortening and less activation following lengthening. Owing to these differences in neuromuscular activation, it is unclear whether perception of effort is altered by the history dependence of force during plantar-flexion. Experiment 1 tested whether perception of effort differed between the rTD and rTE state when Torque was matched. Experiment 2 tested whether perception of effort differed between the rTD and rTE state when EMG was matched. Finally, experiment 3 tested whether EMG differed between the rTD and rTE state when perception of effort was matched. When Torque was matched, both EMG and perception of effort were higher in the rTD compared to rTE state. When EMG was matched, Torque was lower in the rTD compared to rTE state while perception of effort did not differ between the two states. When perception of effort was matched, Torque was lower in the rTD compared to rTE state and EMG did not differ between the two states. The combined results from these experiments indicate that the history dependence of force alters one’s perception of effort, dependent on the level of motor command.

  • perception of effort during an isometric contraction is influenced by prior muscle lengthening or shortening
    bioRxiv, 2021
    Co-Authors: Benjamin Kozlowski, Benjamin Pageaux, Emma F Hubbard, Benjamin St Peters, Philip J Millar, Geoffrey A Power
    Abstract:

    Abstract Purpose Following a shortening or lengthening muscle contraction, the Torque produced in the isometric steady state is distinctly lower (Residual Torque depression; rTD) or higher (Residual Torque enhancement; rTE), respectively, compared to a purely isometric contraction at the same final muscle length and level of activation. This is referred to as the history dependence of force. When matching a given Torque level, there is greater muscle activation (electromyography; EMG) following shortening and less activation following lengthening. Owing to these differences in neuromuscular activation, it is unclear whether perception of effort is altered by the history dependence of force. Methods Experiment 1 tested whether perception of effort differed between the rTD and rTE state when Torque was matched. Experiment 2 tested whether perception of effort differed between the rTD and rTE state when EMG was matched. Finally, experiment 3 tested whether EMG differed between the rTD and rTE state when perception of effort was matched. Results When Torque was matched, both EMG and perception of effort were higher in the rTD compared to rTE state. When EMG was matched, Torque was lower in the rTD compared to rTE state while perception of effort did not differ between the two states. When perception of effort was matched, Torque was lower in the rTD compared to rTE state and EMG did not differ between the two states. Conclusion The combined results from these experiments indicate that the history dependence of force alters one’s perception of effort, dependent on the level of motor command.

  • Residual force enhancement due to active muscle lengthening allows similar reductions in neuromuscular activation during position and force control tasks
    Journal of Sport and Health Science, 2020
    Co-Authors: Rhiannon Marion, Geoffrey A Power
    Abstract:

    Abstract Background Residual Torque enhancement (rTE) is the increase in Torque observed during the isometric steady state following active muscle lengthening when compared with a fixed-end isometric contraction at the same muscle length and level of neuromuscular activation. In the rTE state, owing to an elevated contribution of passive force to total force production, less active force is required, and there is a subsequent reduction in activation. In vivo studies of rTE reporting an activation reduction are often performed using a dynamometer, where participants contract against a rigid restraint, resisting a Torque motor. rTE has yet to be investigated during a position task, which involves the displacement of an inertial load with positional control. Methods A total of 12 participants (6 males, 6 females; age = 22.8 ± 1.1 years, height = 174.7 ± 8.6 cm, mass = 82.1 ± 37.7 kg; mean ± SD) completed Torque- and position-matching tasks at 60% maximum voluntary contraction for a fixed-end isometric contraction and an isometric contraction following active lengthening of the ankle dorsiflexors. Results There were no significant differences in activation between Torque- and position-matching tasks (p = 0.743), with ∼27% activation reduction following active lengthening for both task types (p Conclusion These results indicate that rTE is a feature of voluntary, position-controlled contractions. These findings support and extend previous findings of isometric Torque-control conditions to position-controlled contractions that represent different tasks of daily living.

  • inhibitory tendon evoked reflex is attenuated in the Torque depressed isometric steady state following active shortening
    Applied Physiology Nutrition and Metabolism, 2020
    Co-Authors: Caleb T Sypkes, Brian H Dalton, Joanna Stuart, Geoffrey A Power
    Abstract:

    Residual Torque depression (rTD) is the reduction in steady-state isometric Torque following an active shortening contraction when compared with an isometric contraction at the same muscle length a...

  • the inhibitory tendon evoked reflex is increased in the Torque enhanced state following active lengthening compared to a purely isometric contraction
    Brain Sciences, 2019
    Co-Authors: Vincenzo S Contento, Brian H Dalton, Geoffrey A Power
    Abstract:

    Residual Torque enhancement (rTE) is a history-dependent property of muscle, which results in an increase in steady-state isometric Torque production following an active lengthening contraction as compared to a purely isometric (ISO) contraction at the same muscle length and level of activation. Once thought to be only an intrinsic property of muscle, recent evidence during voluntary contractions indicates a neuromechanical coupling between motor neuron excitability and the contractile state of the muscle. However, the mechanism by which this occurs has yet to be elucidated. The purpose of this study was to investigate inhibition arising from tendon-mediated feedback (e.g., Golgi tendon organ; GTO) through tendon electrical stimulation (TStim) in the ISO and rTE states during activation-matching and Torque-matching tasks. Fourteen male participants (22 ± 2 years) performed 10 activation-matching contractions at 40% of their maximum tibialis anterior electromyography amplitude (5 ISO/5 rTE) and 10 Torque-matching contractions at 40% of their maximum dorsiflexion Torque (5 ISO/5 rTE). During both tasks, 10 TStim were delivered during the isometric steady state of all contractions, and the resulting tendon-evoked inhibitory reflexes were averaged and analyzed. Reflex amplitude increased by ~23% in the rTE state compared to the ISO state for the activation-matching task, and no differences were detected for the Torque-matching task. The current data indicate an important relationship between afferent feedback in the Torque-enhanced state and voluntary control of submaximal contractions. The history-dependent properties of muscle is likely to alter motor neuron excitability through modifications in tension- or Torque-mediated afferent feedback arising from the tendon.

Xm Tao - One of the best experts on this subject based on the ideXlab platform.

  • An experimental study of improving fabric appearance of denim by using low Torque singles ring spun yarns
    SAGE Publications, 2013
    Co-Authors: Hua T, Cheng Kps, Xm Tao, X X Huang
    Abstract:

    This paper presents an experimental study on the improvement of denim fabric appearance by reducing the Residual Torque of weft yarns. In this paper, 100% cotton low Torque yarns of linear density 84 tex and 58 tex with different twist levels were produced by a new method of producing low Torque yarns on a modified ring spinning machine. The results from the experiments show that the low Torque yarns possess lower yarn snarling turns. Based on the mechanism analysis of 'small snake' pattern, the low Torque ring yarns were applied to the denim fabric to improve fabric smoothness appearance. The experimental study demonstrates that the 'small snake' pattern of the denim fabrics has been greatly decreased by using the low Residual Torque ring yarns as weft yarns. Objective measurements of the low stress mechanical and surface properties of denim fabrics using low Torque and conventional yarns were conducted. The results show that the denim fabric using the low Torque ring yarns as weft yarns presents a smoother and more even surface. Moreover, a multiple comparisons LSD test of fabric properties indicates that there is no significant difference on tensile strength and tearing strength between fabric samples using the low Torque ring yarns and conventional ring yarns with normal twist level as weft yarns, respectively. In addition, the experimental results demonstrate that the 'small snake' pattern of the fabric decreased with the reduction of weft yarn snarling.Institute of Textiles and Clothin

  • An artificial neural network model for the prediction of spirality of fully relaxed single jersey fabrics
    SAGE Publications, 2009
    Co-Authors: Cm Murrells, Xm Tao, Cheng Kps
    Abstract:

    The present paper proposes an artificial neural network model for the prediction of the degree of spirality of single jersey fabrics made from 100 % cotton conventional and modified ring spun yarns. The factors investigated were the yarn Residual Torque as the measured twist liveliness, yarn type, yarn linear density, fabric tightness factor, the number of feeders, rotational direction and gauge of the knitting machine and dyeing method. The artificial neural network model was compared with a multiple regression model, demonstrating that the neural network model produced superior results to predict the degree of fabric spirality after three washing and drying cycles. The relative importance of the investigated factors influencing the spirality of the fabric was also investigated.Institute of Textiles and Clothin

  • Techniques for Torque modification of singles ring spun yarns
    SAGE Publications, 2008
    Co-Authors: Xm Tao
    Abstract:

    This article reports on a systematic study of various spinning techniques to produce Torque-free singles ring spun yarns on a modified ring frame. The modification units, including optional fiber separation devices and a false twist device, were incorporated into the conventional ring spinning frame so that the balanced or reduced yarn Residual Torque could be achieved in one step. Three modification systems were proposed and two of them were investigated on a ring frame to produce pure cotton singles yarns. The spirality of the resultant single jersey knit fabrics was greatly reduced. Properties and performance characteristics of control and modified yarns, as well as their resultant fabrics, were evaluated, including yarn tensile properties, hairiness, evenness, snarling, burst strength, air permeability, handle, and pill resistances.Institute of Textiles and Clothin

  • Torque-balanced singles knitting yarns spun by unconventional systems - Part II : Cotton friction spun DREF III yarn
    SAGE Publications, 1997
    Co-Authors: Ym Lau, Xm Tao
    Abstract:

    This paper is concerned with the application of a modification process to cotton friction spun singles yarns. The experimental results show that the yarn modification process can effectively reduce or eliminate Residual Torque in DREF-III singles yarns as well as fabric spirality in plain knitted structures. The properties and performance characteristics of yarns and fabrics are evaluated, including hairiness, diameter, evenness, tensile properties, and twist liveliness of the yarns, and thickness, weight, air permeability, thermal conductivity, bursting strength, and pilling resistance of the fabrics. The effects of yarn production parameters, relaxation, and modification processes are also discussed.Institute of Textiles and Clothin

Zhen Zhang - One of the best experts on this subject based on the ideXlab platform.

  • contact acoustic nonlinearity can based continuous monitoring of bolt loosening hybrid use of high order harmonics and spectral sidebands
    Mechanical Systems and Signal Processing, 2018
    Co-Authors: Zhen Zhang, Menglong Liu, Yaozhong Liao, Yi Xiao
    Abstract:

    Abstract The significance of evaluating bolt tightness in engineering structures, preferably in a continuous manner, cannot be overemphasized. With hybrid use of high-order harmonics ( HOH ) and spectral sidebands, a contact acoustic nonlinearity ( CAN )-based monitoring framework is developed for detecting bolt loosening and subsequently evaluating the Residual Torque on a loose bolt. Low-frequency pumping vibration is introduced into the bolted joint to produce a “breathing” effect at the joining interface that modulates the propagation characteristics of a high-frequency probing wave when it traverses the bolt, leading to the generation of HOH and vibro-acoustic nonlinear distortions (manifested as sidebands in the signal spectrum). To gain insight into the mechanism of CAN generation and to correlate the acquired nonlinear responses of a loose joint with the Residual Torque remaining on the bolt, an analytical model based on micro-contact theory is established. Two types of nonlinear index, respectively exploiting the induced HOH and spectral sidebands, are defined without dependence on excitation intensity and are experimentally demonstrated to be effective in continuously monitoring bolt loosening in both aluminum-aluminum and composite-composite bolted joints. Taking a step further, variation of the index pair is quantitatively associated with the Residual Torque on a loose bolt. The approach developed provides a reliable method of continuous evaluation of bolt tightness in both composite and metallic joints, regardless of their working conditions, from early awareness of bolt loosening at an embryonic stage to quantitative estimation of Residual Torque.

  • quantitative evaluation of Residual Torque of a loose bolt based on wave energy dissipation and vibro acoustic modulation a comparative study
    Journal of Sound and Vibration, 2016
    Co-Authors: Zhen Zhang, Menglong Liu, Yi Xiao
    Abstract:

    Abstract A wave energy dissipation (WED)-based linear acoustic approach and a vibro-acoustic modulation (VM)-based nonlinear method were developed comparatively, for detecting bolt loosening in bolted joints and subsequently evaluating the Residual Torque of the loose bolt. For WED-based, an analytical model residing on the Hertzian contact theory was established, whereby WED was linked to the Residual Torque of a loose bolt, contributing to a linear index. For VM-based, contact acoustic nonlinearity (CAN) engendered at the joining interface, when a pumping vibration perturbs a probing wave, was interrogated, and the nonlinear contact stiffness was described in terms of a Taylor series, on which basis a nonlinear index was constructed to associate spectral features with the Residual Torque. Based respectively on a linear and a nonlinear premise, the two indices were validated experimentally, and the results well coincided with theoretical predication. Quantitative comparison of the two indices surmises that the VM-based nonlinear method outperforms the WED-based linear approach in terms of sensitivity and accuracy, and particularly when the bolt loosening is in its embryo stage. In addition, the detectability of the nonlinear index is not restricted by the type of the joint, against a high dependence of its linear counterpart on the joint type.

Yi Xiao - One of the best experts on this subject based on the ideXlab platform.

  • contact acoustic nonlinearity can based continuous monitoring of bolt loosening hybrid use of high order harmonics and spectral sidebands
    Mechanical Systems and Signal Processing, 2018
    Co-Authors: Zhen Zhang, Menglong Liu, Yaozhong Liao, Yi Xiao
    Abstract:

    Abstract The significance of evaluating bolt tightness in engineering structures, preferably in a continuous manner, cannot be overemphasized. With hybrid use of high-order harmonics ( HOH ) and spectral sidebands, a contact acoustic nonlinearity ( CAN )-based monitoring framework is developed for detecting bolt loosening and subsequently evaluating the Residual Torque on a loose bolt. Low-frequency pumping vibration is introduced into the bolted joint to produce a “breathing” effect at the joining interface that modulates the propagation characteristics of a high-frequency probing wave when it traverses the bolt, leading to the generation of HOH and vibro-acoustic nonlinear distortions (manifested as sidebands in the signal spectrum). To gain insight into the mechanism of CAN generation and to correlate the acquired nonlinear responses of a loose joint with the Residual Torque remaining on the bolt, an analytical model based on micro-contact theory is established. Two types of nonlinear index, respectively exploiting the induced HOH and spectral sidebands, are defined without dependence on excitation intensity and are experimentally demonstrated to be effective in continuously monitoring bolt loosening in both aluminum-aluminum and composite-composite bolted joints. Taking a step further, variation of the index pair is quantitatively associated with the Residual Torque on a loose bolt. The approach developed provides a reliable method of continuous evaluation of bolt tightness in both composite and metallic joints, regardless of their working conditions, from early awareness of bolt loosening at an embryonic stage to quantitative estimation of Residual Torque.

  • quantitative evaluation of Residual Torque of a loose bolt based on wave energy dissipation and vibro acoustic modulation a comparative study
    Journal of Sound and Vibration, 2016
    Co-Authors: Zhen Zhang, Menglong Liu, Yi Xiao
    Abstract:

    Abstract A wave energy dissipation (WED)-based linear acoustic approach and a vibro-acoustic modulation (VM)-based nonlinear method were developed comparatively, for detecting bolt loosening in bolted joints and subsequently evaluating the Residual Torque of the loose bolt. For WED-based, an analytical model residing on the Hertzian contact theory was established, whereby WED was linked to the Residual Torque of a loose bolt, contributing to a linear index. For VM-based, contact acoustic nonlinearity (CAN) engendered at the joining interface, when a pumping vibration perturbs a probing wave, was interrogated, and the nonlinear contact stiffness was described in terms of a Taylor series, on which basis a nonlinear index was constructed to associate spectral features with the Residual Torque. Based respectively on a linear and a nonlinear premise, the two indices were validated experimentally, and the results well coincided with theoretical predication. Quantitative comparison of the two indices surmises that the VM-based nonlinear method outperforms the WED-based linear approach in terms of sensitivity and accuracy, and particularly when the bolt loosening is in its embryo stage. In addition, the detectability of the nonlinear index is not restricted by the type of the joint, against a high dependence of its linear counterpart on the joint type.

X X Huang - One of the best experts on this subject based on the ideXlab platform.

  • an experimental study of improving fabric appearance of denim by using low Torque singles ring spun yarns
    Textile Research Journal, 2013
    Co-Authors: Kwok Po Stephen Cheng, Bingang Xu, X X Huang
    Abstract:

    This paper presents an experimental study on the improvement of denim fabric appearance by reducing the Residual Torque of weft yarns. In this paper, 100% cotton low Torque yarns of linear density ...

  • An experimental study of improving fabric appearance of denim by using low Torque singles ring spun yarns
    SAGE Publications, 2013
    Co-Authors: Hua T, Cheng Kps, Xm Tao, X X Huang
    Abstract:

    This paper presents an experimental study on the improvement of denim fabric appearance by reducing the Residual Torque of weft yarns. In this paper, 100% cotton low Torque yarns of linear density 84 tex and 58 tex with different twist levels were produced by a new method of producing low Torque yarns on a modified ring spinning machine. The results from the experiments show that the low Torque yarns possess lower yarn snarling turns. Based on the mechanism analysis of 'small snake' pattern, the low Torque ring yarns were applied to the denim fabric to improve fabric smoothness appearance. The experimental study demonstrates that the 'small snake' pattern of the denim fabrics has been greatly decreased by using the low Residual Torque ring yarns as weft yarns. Objective measurements of the low stress mechanical and surface properties of denim fabrics using low Torque and conventional yarns were conducted. The results show that the denim fabric using the low Torque ring yarns as weft yarns presents a smoother and more even surface. Moreover, a multiple comparisons LSD test of fabric properties indicates that there is no significant difference on tensile strength and tearing strength between fabric samples using the low Torque ring yarns and conventional ring yarns with normal twist level as weft yarns, respectively. In addition, the experimental results demonstrate that the 'small snake' pattern of the fabric decreased with the reduction of weft yarn snarling.Institute of Textiles and Clothin