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Shirato R, Shimanuki R, Shoji T, Mugikura M. Inhibitory Effects of Prolonged Focal Muscle Vibration on Maximal Grip Strength and Muscle Activity of Wrist and Extrinsic Finger Flexor Muscles. J Chiropr Med 2023; 22:107-115. [PMID: 37346243 PMCID: PMC10280089 DOI: 10.1016/j.jcm.2023.03.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 03/14/2023] [Accepted: 03/20/2023] [Indexed: 06/23/2023] Open
Abstract
Objective The objective of this study was to identify effective stimulus time by quantifying the inhibitory effects of focal muscle vibration (FMV) on maximal grip strength and muscle activities of the wrist and extrinsic finger flexors. Methods A randomized repeated-measures design was used in this study. A total of 22 healthy volunteers (mean age, 20.9 years) participated. An FMV of 86 Hz was applied to the anterior surface of the distal forearm under the following 3 conditions: no FMV (control), 5-minute FMV, and 10-minute FMV. Maximal grip strength was measured before and after FMV. The muscle activities of the flexor digitorum superficialis, flexor digitorum profundus (FDP), and flexor carpi ulnaris were simultaneously recorded using surface electromyography. Discomfort and complications following FMV were also assessed. Results Compared with the control group, a significant decrease in muscle activity was observed in both the flexor digitorum superficialis and flexor carpi ulnaris after 5 and 10 minutes of FMV. In contrast, there was no significant decrease in the maximal grip strength or FDP muscle activity after either FMV condition. The discomfort was significantly higher immediately after both FMV conditions than in the control group, but it decreased 15 minutes after FMV, indicating no significant difference among the 3 conditions. Redness and/or swelling were observed in 13.6% and 36.3% of the participants after 5 and 10 minutes of FMV, respectively. Conclusion Five-minute FMV to the distal forearm could be a useful therapeutic method with few complications. However, the FMV in this area alone was not sufficient to suppress the muscle activity of the FDP located in the deep layer.
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Affiliation(s)
- Rikiya Shirato
- Department of Rehabilitation, Faculty of Healthcare and Science, Hokkaido Bunkyo University, Eniwa, Japan
| | - Ren Shimanuki
- Department of Occupational Therapy, Tokeidai Memorial Hospital, Sapporo, Japan
| | - Towa Shoji
- Department of Rehabilitation, Hokkaido Saiseikai Midori-no-Sato, Otaru, Japan
| | - Masaki Mugikura
- Department of Rehabilitation, Hanakawa Hospital, Ishikari, Japan
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Nagamori A, Laine CM, Loeb GE, Valero-Cuevas FJ. Force variability is mostly not motor noise: Theoretical implications for motor control. PLoS Comput Biol 2021; 17:e1008707. [PMID: 33684099 PMCID: PMC7971898 DOI: 10.1371/journal.pcbi.1008707] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/11/2020] [Revised: 03/18/2021] [Accepted: 01/15/2021] [Indexed: 11/19/2022] Open
Abstract
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.
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Affiliation(s)
- Akira Nagamori
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California, United States of America
| | - Christopher M. Laine
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California, United States of America
- Chan Division of Occupational Science and Occupational Therapy, University of Southern California, Los Angeles, California, United States of America
| | - Gerald E. Loeb
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, United States of America
| | - Francisco J. Valero-Cuevas
- Division of Biokinesiology and Physical Therapy, University of Southern California, Los Angeles, California, United States of America
- Department of Biomedical Engineering, University of Southern California, Los Angeles, California, United States of America
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Suzuki R, Kanehisa H, Washino S, Watanabe H, Shinohara M, Yoshitake Y. Reconstruction of net force fluctuations from surface EMGs of multiple muscles in steady isometric plantarflexion. Exp Brain Res 2021; 239:601-612. [PMID: 33388812 DOI: 10.1007/s00221-020-05987-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2020] [Accepted: 11/13/2020] [Indexed: 12/22/2022]
Abstract
The purposes of this study were to clarify if force fluctuations during steady multi-muscle contractions have a temporal correlation with a low-frequency component of rectified surface EMG (rEMG) in the involved muscles and collection of that component across muscles allows for the reconstruction of force fluctuations across a wide range of contraction intensities. Healthy young men (n = 15) exerted steady isometric plantarflexion force at 5-60% of maximal force. Surface EMG was recorded from the medial and lateral gastrocnemii, soleus, peroneus longus, abductor hallucis, and tibialis anterior muscles. The cross-correlation function (CCF) between plantarflexion force fluctuations and low-pass filtered rEMG in each muscle was calculated for 8 s. To reconstruct force fluctuations from rEMGs, the product of rEMG and an identified constant factor were summed across muscles with time-lag compensation for electro-mechanical delay. A distinct peak of the CCF was found between plantarflexion force fluctuations and rEMG in most cases except for the tibialis anterior. The CCF peak was greatest in the medial gastrocnemius and soleus. Reconstructed force from rEMGs was temporally correlated with measured force fluctuations across contraction intensities (average CCF peak: r = 0.65). The results indicate that individual surface rEMG has a low-frequency component that is temporally correlated with net force fluctuations during steady multi-muscle contractions and contributes to the reconstruction of force fluctuations across a wide range of contraction intensities. It suggests a potential applicability of individual surface EMGs for identifying the contributing muscles to controlling or disturbing isometric steady force in multi-muscle contractions.
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Affiliation(s)
- Ryosei Suzuki
- Graduate School of Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano, 3860018, Japan
| | - Hiroaki Kanehisa
- School of Sports and Health Sciences, Ritsumeikan University, 1-1-1 Nozihigashi, Kusatsu, Shiga, 5258577, Japan
| | - Sohei Washino
- Human Augmentation Research Center, National Institute of Advanced Industrial Science and Technology, 6-2-3 Kashiwanoha, Kashiwa, Chiba, 2770882, Japan
| | - Hironori Watanabe
- Department of Biomedical Engineering, Toyo University, 2100 Kujirai, Kawagoe, Saitama, 3508585, Japan
| | - Minoru Shinohara
- School of Biological Sciences, Georgia Institute of Technology, 555 14th St NW, Atlanta, GA, 30332, USA
| | - Yasuhide Yoshitake
- Graduate School of Science and Technology, Shinshu University, 3-15-1 Tokida, Ueda, Nagano, 3860018, Japan. .,School of Human Movement and Nutrition Sciences, The University of Queensland, St Lucia, Brisbane, QLD, 4072, Australia.
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Acute effect of tendon vibration applied during isometric contraction at two knee angles on maximal knee extension force production. PLoS One 2020; 15:e0242324. [PMID: 33186411 PMCID: PMC7665630 DOI: 10.1371/journal.pone.0242324] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2019] [Accepted: 11/02/2020] [Indexed: 11/19/2022] Open
Abstract
The aim of the current study was to investigate the effect of a single session of prolonged tendon vibration combined with low submaximal isometric contraction on maximal motor performance. Thirty-two young sedentary adults were assigned into two groups that differed based on the knee angle tested: 90° or 150° (180° = full knee extension). Participants performed two fatigue-inducing exercise protocols: one with three 10 min submaximal (10% of maximal voluntary contraction) knee extensor contractions and patellar tendon vibration (80 Hz) another with submaximal knee extensor contractions only. Before and after each fatigue protocol, maximal voluntary isometric contractions (MVC), voluntary activation level (assessed by the twitch interpolation technique), peak-to-peak amplitude of maximum compound action potentials of vastus medialis and vastus lateralis (assessed by electromyography with the use of electrical nerve stimulation), peak twitch amplitude and peak doublet force were measured. The knee extensor fatigue was significantly (P<0.05) greater in the 90° knee angle group (-20.6% MVC force, P<0.05) than the 150° knee angle group (-8.3% MVC force, P = 0.062). Both peripheral and central alterations could explain the reduction in MVC force at 90° knee angle. However, tendon vibration added to isometric contraction did not exacerbate the reduction in MVC force. These results clearly demonstrate that acute infrapatellar tendon vibration using a commercial apparatus operating at optimal conditions (i.e. contracted and stretched muscle) does not appear to induce knee extensor neuromuscular fatigue in young sedentary subjects.
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Diabetes Mellitus-Related Dysfunction of the Motor System. Int J Mol Sci 2020; 21:ijms21207485. [PMID: 33050583 PMCID: PMC7589125 DOI: 10.3390/ijms21207485] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2020] [Revised: 10/08/2020] [Accepted: 10/08/2020] [Indexed: 12/20/2022] Open
Abstract
Although motor deficits in humans with diabetic neuropathy have been extensively researched, its effect on the motor system is thought to be lesser than that on the sensory system. Therefore, motor deficits are considered to be only due to sensory and muscle impairment. However, recent clinical and experimental studies have revealed that the brain and spinal cord, which are involved in the motor control of voluntary movement, are also affected by diabetes. This review focuses on the most important systems for voluntary motor control, mainly the cortico-muscular pathways, such as corticospinal tract and spinal motor neuron abnormalities. Specifically, axonal damage characterized by the proximodistal phenotype occurs in the corticospinal tract and motor neurons with long axons, and the transmission of motor commands from the brain to the muscles is impaired. These findings provide a new perspective to explain motor deficits in humans with diabetes. Finally, pharmacological and non-pharmacological treatment strategies for these disorders are presented.
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Baudry S, Duchateau J. Aftereffects of prolonged Achilles tendon vibration on postural control are reduced in older adults. Exp Gerontol 2020; 131:110822. [PMID: 31899339 DOI: 10.1016/j.exger.2019.110822] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/26/2019] [Revised: 12/21/2019] [Accepted: 12/26/2019] [Indexed: 11/16/2022]
Abstract
AIM To assess the change in the contribution of proprioceptive signal from leg muscles in postural control with ageing. METHODS Fifteen young (~23 yr) and fifteen older adults (~68 yr) participated in Experiment 1, which consisted of recording the mean position of the centre of pressure (CoP), CoP path length, CoP velocity, and the amplitude of the Hoffmann (H) reflex and maximal M wave (MMAX) in the soleus muscle during upright standing, before and after 1 h of bilateral Achilles tendon vibration applied in seated posture. Eight young (~24 yr) and eight older adults (~67 yr) participated in Experiment 2 consisting of recording H-reflex and MMAX in seated posture before and after the 1-h vibration procedure used in Experiment 1. RESULTS Immediately after the 1-h vibration, the mean CoP position shifted forward in both groups (p < 0.05), with a greater magnitude of change (% pre-vibration) in young [mean(SD); 74(41)%] than older adults [44(40)%; p < 0.05]. The CoP path length and velocity only increased in young adults after vibration (p < 0.05). The H-reflex amplitude decreased only in young adults after vibration [before: 35(12); after: 16(13)% Mmax, p < 0.05] during upright standing (Experiment 1), whereas it decreased similarly (p > 0.05) in young [before: 47(12)% Mmax; after: 28(17)% Mmax] and older adults [before: 34(13)% Mmax; after: 21(14)% Mmax] in seated posture (Experiment 2). CONCLUSION Prolonged Achilles tendon vibrations lead to lesser postural perturbation in older than in young adults, supporting the assumption of a decreased reliance on leg muscle proprioception in postural control with ageing.
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Affiliation(s)
- Stéphane Baudry
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 route de Lennik, 1070 Brussels, Belgium.
| | - Jacques Duchateau
- Laboratory of Applied Biology, Research Unit in Applied Neurophysiology, ULB-Neurosciences Institute (UNI), Université Libre de Bruxelles (ULB), 808 route de Lennik, 1070 Brussels, Belgium
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Shirato R, Sakamoto H, Sugiyama T, Suzuki M, Takahashi R, Tanaka T. Inhibitory Effects of Prolonged Vibratory Stimulus on the Maximal Voluntary Contraction Force and Muscle Activity of the Triceps Brachii: An Experimental Study. J Chiropr Med 2019; 18:97-105. [DOI: 10.1016/j.jcm.2018.10.003] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/07/2018] [Revised: 09/19/2018] [Accepted: 10/28/2018] [Indexed: 11/28/2022] Open
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Washino S, Mankyu H, Kanehisa H, Mayfield DL, Cresswell AG, Yoshitake Y. Effects of inspiratory muscle strength and inspiratory resistance on neck inspiratory muscle activation during controlled inspirations. Exp Physiol 2019; 104:556-567. [PMID: 30714220 DOI: 10.1113/ep087247] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2018] [Accepted: 02/01/2019] [Indexed: 11/08/2022]
Abstract
NEW FINDINGS What is the central question of this study? What factors influence the onset and magnitude of activation of the neck inspiratory muscles during inspiration? What is the main finding and its importance? Recruitment of the sternocleidomastoid and scalene muscles during inspiration, measured by means of surface EMG, was strongly correlated with maximal inspiratory pressure. This result indicates that muscle recruitment depends on the capacity of an individual to generate inspiratory pressure. Surface measurements of neck inspiratory muscle EMG activity might complement tests currently used for the screening of respiratory-related disease. ABSTRACT The aims of the present study were as follows: (i) to examine the relationship between the onset of recruitment of the neck inspiratory muscles and inspiratory muscle strength; and (ii) to clarify the effect of inspiratory resistance on neck inspiratory muscle activation during inspiration at specific flow rates and to specific lung volumes. Inspiratory muscle strength, as indicated by maximal inspiratory pressure (MIP), and peak inspiratory flow rate (PFR) were measured in healthy participants. Subsequently, participants inspired at target inspiratory flow rates between 20 and 100% of PFR as closely as possible, with and without artificial inspiratory resistance. Electromyographic activity (EMGRMS ) of the sternocleidomastoid and scalene muscles was measured from surface electrodes at each target flow rate for each 10% increment of forced vital capacity (FVC) between 20 and 50% of FVC. Recruitment onset for each muscle was determined from %PFR-EMGRMS curves at each lung volume (%FVC). Finally, linear regression analyses were performed for MIP and recruitment onset for each muscle at each %FVC. Recruitment onset during inspiration without inspiratory resistance was strongly correlated with MIP (r > 0.60, P < 0.040). Specifically, a lower MIP was associated with earlier muscle recruitment (i.e. recruitment at a lower flow rate), especially for the sternocleidomastoid muscle (r > 0.75, P < 0.005). Recruitment of both neck inspiratory muscles at a given flow rate was also earlier when inspiratory resistance was added (P = 0.002). These results indicate that the recruitment and activation of the neck inspiratory muscles depends on both inspiratory muscle strength and inspiratory resistance.
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Affiliation(s)
- Sohei Washino
- Graduate School of Physical Education, National Institute of Fitness and Sports in Kanoya, Kanoya, Kagoshima, Japan
| | - Hirotoshi Mankyu
- Department of Coaching of Sports and Budo, National Institute of Fitness and Sports in Kanoya, Kanoya, Kagoshima, Japan
| | - Hiroaki Kanehisa
- Department of Sports and Life Sciences, National Institute of Fitness and Sports in Kanoya, Kanoya, Kagoshima, Japan
| | - Dean L Mayfield
- School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Andrew G Cresswell
- School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Queensland, Australia
| | - Yasuhide Yoshitake
- Department of Sports and Life Sciences, National Institute of Fitness and Sports in Kanoya, Kanoya, Kagoshima, Japan.,School of Human Movement and Nutrition Sciences, The University of Queensland, Brisbane, Queensland, Australia.,Graduate School of Science and Technology, Shinshu University, Ueda, Nagano, Japan
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Souron R, Oriol M, Millet GY, Lapole T. Intermediate Muscle Length and Tendon Vibration Optimize Corticospinal Excitability During Knee Extensors Local Vibration. Front Physiol 2018; 9:1266. [PMID: 30233417 PMCID: PMC6134995 DOI: 10.3389/fphys.2018.01266] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/30/2018] [Accepted: 08/21/2018] [Indexed: 11/23/2022] Open
Abstract
While local vibration (LV) has been recently proposed as a potential modality for neuromuscular conditioning, no practical recommendations to optimize its effects have been published. Because changes in corticospinal excitability may reflect at which degree the neuromuscular function is modulated during LV exposure, this study investigated the effects of muscle length and vibration site on LV-induced on motor evoked potentials (MEPs) changes. Twenty-one subjects participated in a single session in which MEPs were evoked on the relaxed knee extensors (KE) during three conditions, i.e., no vibration (CON), muscle (VIBMU), and tendon vibration (VIBTD). Three muscle lengths were tested for each condition, i.e., short/intermediate/long KE muscle length. Both VIBMU and VIBTD significantly increase MEPs compared to CON. Higher increases (P < 0.001) were found for VIBTD compared to VIBMU for vastus lateralis (mean increases of the three angles: +241% vs.+ 148%), vastus medialis (+273% vs. + 180%) and rectus femoris muscles (+191% vs. +141%). The increase in MEPs amplitude was higher (p < 0.001) at an intermediate (mean pooled increase for VIBTD and VIBMU: +265%, +290%, and +212% for VL, VM, and RF, respectively) compared to short (+136%, + 144%, and + 127%) or long (+ 184%, + 246% and + 160%) muscle lengths. These results suggest that LV should be applied to the tendon at an intermediate muscle length to optimize the acute effects of LV on the KE neuromuscular function.
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Affiliation(s)
- Robin Souron
- Univ Lyon, UJM Saint-Etienne, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F-42023, Saint-Étienne, France
| | - Marie Oriol
- Univ Lyon, UJM Saint-Etienne, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F-42023, Saint-Étienne, France
| | - Guillaume Y. Millet
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
| | - Thomas Lapole
- Univ Lyon, UJM Saint-Etienne, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F-42023, Saint-Étienne, France
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Yoshitake Y, Ikeda A, Shinohara M. Robotic finger perturbation training improves finger postural steadiness and hand dexterity. J Electromyogr Kinesiol 2017; 38:208-214. [PMID: 29199081 DOI: 10.1016/j.jelekin.2017.11.011] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/02/2017] [Revised: 10/25/2017] [Accepted: 11/16/2017] [Indexed: 11/28/2022] Open
Abstract
The purpose of the study was to understand the effect of robotic finger perturbation training on steadiness in finger posture and hand dexterity in healthy young adults. A mobile robotic finger training system was designed to have the functions of high-speed mechanical response, two degrees of freedom, and adjustable loading amplitude and direction. Healthy young adults were assigned to one of the three groups: random perturbation training (RPT), constant force training (CFT), and control. Subjects in RPT and CFT performed steady posture training with their index finger using the robot in different modes: random force in RPT and constant force in CFT. After the 2-week intervention period, fluctuations of the index finger posture decreased only in RPT during steady position-matching tasks with an inertial load. Purdue pegboard test score improved also in RPT only. The relative change in finger postural fluctuations was negatively correlated with the relative change in the number of completed pegs in the pegboard test in RPT. The results indicate that finger posture training with random mechanical perturbations of varying amplitudes and directions of force is effective in improving finger postural steadiness and hand dexterity in healthy young adults.
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Affiliation(s)
- Yasuhide Yoshitake
- Department of Sports and Life Sciences, National Institute of Fitness and Sports in Kanoya, Kagoshima, Japan
| | - Atsutoshi Ikeda
- Department of Mechanical Engineering, Kindai University, Osaka, Japan; Graduate School of Information Science, Nara Institute of Science and Technology, Nara, Japan
| | - Minoru Shinohara
- School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA, USA; Research Center for Advanced Science and Technology, University of Tokyo, Tokyo, Japan.
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Souron R, Besson T, McNeil CJ, Lapole T, Millet GY. An Acute Exposure to Muscle Vibration Decreases Knee Extensors Force Production and Modulates Associated Central Nervous System Excitability. Front Hum Neurosci 2017; 11:519. [PMID: 29118698 PMCID: PMC5660984 DOI: 10.3389/fnhum.2017.00519] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2017] [Accepted: 10/11/2017] [Indexed: 01/25/2023] Open
Abstract
Local vibration (LV) has been recently validated as an efficient training method to improve muscle strength. Understanding the acute effects may help elucidate the mechanism(s). This study aimed to investigate the effects of a single bout of prolonged LV on knee extensor force production and corticospinal responsiveness of vastus lateralis (VL) and rectus femoris (RF) muscles in healthy young and old adults. Across two visits, 23 adult subjects (20-75 years old) performed pre- and post-test measurements, separated by 30-min of either rest (control; CON) or LV. Maximal voluntary contraction (MVC) force was assessed and transcranial magnetic stimulation (TMS) was used to evaluate cortical voluntary activation (VATMS) as well as the motor evoked potential (MEP) and silent period (SP). In 11 young adults, thoracic electrical stimulation was used to assess the thoracic motor evoked potential (TMEP). Although MVC decreased after both CON (-6.3 ± 4.4%, p = 0.01) and LV (-12.9 ± 7.7%, p < 0.001), the MVC loss was greater after LV (p = 0.001). Normalized maximal electromyographic (EMG) activity decreased after LV for both VL (-25.1 ± 10.7%) and RF (-20.9 ± 16.5%; p < 0.001), while it was unchanged after CON (p = 0.32). For RF, the TMEP and MEP/TMEP ratio decreased (p = 0.01) and increased (p = 0.01) after LV, respectively. Both measures were unchanged for VL (p = 0.27 and p = 0.15, respectively). No changes were reported for TMS-related parameters. These results confirm our hypothesis that modulations within the central nervous system would accompany the significant reduction of maximal voluntary force. A reduced motoneuron excitability seems to explain the decreased MVC after prolonged LV, as suggested by reductions in maximal EMG (all subjects) and TMEP area (data from 11 young subjects). A concomitant increased cortical excitability seems to compensate for lower excitability at the spinal level.
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Affiliation(s)
- Robin Souron
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
- Laboratoire Interuniversitaire de Biologie de la Motricité, UJM Saint-Etienne, University Lyon, Saint-Etienne, France
| | - Thibault Besson
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
- Laboratoire Interuniversitaire de Biologie de la Motricité, UJM Saint-Etienne, University Lyon, Saint-Etienne, France
| | - Chris J. McNeil
- School of Health and Exercise Sciences, University of British Columbia, Kelowna, BC, Canada
| | - Thomas Lapole
- Laboratoire Interuniversitaire de Biologie de la Motricité, UJM Saint-Etienne, University Lyon, Saint-Etienne, France
| | - Guillaume Y. Millet
- Human Performance Laboratory, Faculty of Kinesiology, University of Calgary, Calgary, AB, Canada
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Local vibration inhibits H-reflex but does not compromise manual dexterity and does not increase tremor. Hum Mov Sci 2017; 55:221-228. [PMID: 28843638 DOI: 10.1016/j.humov.2017.08.018] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2017] [Revised: 08/21/2017] [Accepted: 08/21/2017] [Indexed: 11/21/2022]
Abstract
The present work aimed at investigating the effects of local vibration on upper limb postural and kinetic tremor, on manual dexterity and on spinal reflex excitability. Previous studies have demonstrated a decrease in spinal reflex excitability and in force fluctuations in the lower limb but an increase in force fluctuation in the upper limbs. As hand steadiness is of vital importance in many daily-based tasks, and local vibration may also be applied in movement disorders, we decided to further explore this phenomenon. Ten healthy volunteers (26±3years) were tested for H reflex, postural and kinetic tremor and manual dexterity through a Purdue test. EMG was recorded from flexor carpi radialis (FCR) and extensor digitorum communis (EDC). Measurements were repeated at baseline, after a control period during which no vibration was delivered and after vibration. Intervention consisted in holding for two minutes a vibrating handle (frequency 75Hz, displacement∼7mm), control consisted in holding for two minutes the same handle powered off. Reflex excitability decreased after vibration whilst postural tremor and manual dexterity were not affected. Peak kinetic tremor frequency increased from baseline to control measurements (P=0.002). Co-activation EDC/FCR increased from control to vibration (P=0.021). These results show that two minutes local vibration lead to a decrease in spinal excitability, did not compromise manual dexterity and did not increase tremor; however, in contrast with expectations, tremor did not decrease. It is suggested that vibration activated several mechanisms with opposite effects, which resulted in a neutral outcome on postural and kinetic tremor.
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Washino S, Kanehisa H, Yoshitake Y. Neck inspiratory muscle activation patterns during well-controlled inspiration. Eur J Appl Physiol 2017; 117:2085-2097. [PMID: 28823081 DOI: 10.1007/s00421-017-3699-5] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2017] [Accepted: 08/11/2017] [Indexed: 12/12/2022]
Abstract
PURPOSE Surprisingly, the activation characteristics of the neck inspiratory muscles as a function of key inspiratory mechanical parameters have yet to be demonstrated experimentally under well-controlled conditions. This study aimed to elucidate the muscle activation patterns of the neck inspiratory muscles by strictly controlling flow rate and lung volume. METHODS Thirteen healthy subjects matched their inspiratory flow rate at approximately 20-100% of peak flow rate (PFR) as steady as possible during inspiration. Amplitude of surface electromyogram (EMG) of the sternocleidomastoid (SCM) and scalene were calculated for every increase in %PFR over a duration corresponding to an increase in lung volume by 10% of forced vital capacity (FVC), as well as for every 5% increment of FVC over a point corresponding to an increase in flow rate by 20%PFR to determine the %PFR-EMG and %FVC-EMG relations, respectively. RESULTS Regression analyses showed that EMGs of the neck inspiratory muscles exponentially increased with increase in %PFR and their associated variables which reflect recruitment onset when increasing flow rate increased with increasing %FVC. In %FVC-EMG relation, a linear regression analysis showed positive slope at all %PFR and positive y-intercept at 80% PFR. CONCLUSIONS The main new finding is that the neck inspiratory muscle activities increase with flow rate as well as lung volume. The positive y-intercept of the %FVC-EMG relation at higher %PFR indicates that the neck inspiratory muscles are always activated even when lung volume level is low, implying that SCM is not necessarily an "accessory" muscle as described in previous observations.
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Affiliation(s)
- Sohei Washino
- Graduate School of Physical Education, National Institute of Fitness and Sports in Kanoya, 1 Shiromizu, Kanoya, Kagoshima, 8912393, Japan
| | - Hiroaki Kanehisa
- Department of Sports and Life Sciences, National Institute of Fitness and Sports in Kanoya, 1 Shiromizu, Kanoya, Kagoshima, 8912393, Japan
| | - Yasuhide Yoshitake
- Department of Sports and Life Sciences, National Institute of Fitness and Sports in Kanoya, 1 Shiromizu, Kanoya, Kagoshima, 8912393, Japan.
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Acute and chronic neuromuscular adaptations to local vibration training. Eur J Appl Physiol 2017; 117:1939-1964. [PMID: 28766150 DOI: 10.1007/s00421-017-3688-8] [Citation(s) in RCA: 58] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2017] [Accepted: 07/22/2017] [Indexed: 12/19/2022]
Abstract
Vibratory stimuli are thought to have the potential to promote neural and/or muscular (re)conditioning. This has been well described for whole-body vibration (WBV), which is commonly used as a training method to improve strength and/or functional abilities. Yet, this technique may present some limitations, especially in clinical settings where patients are unable to maintain an active position during the vibration exposure. Thus, a local vibration (LV) technique, which consists of applying portable vibrators directly over the tendon or muscle belly without active contribution from the participant, may present an alternative to WBV. The purpose of this narrative review is (1) to provide a comprehensive overview of the literature related to the acute and chronic neuromuscular changes associated with LV, and (2) to show that LV training may be an innovative and efficient alternative method to the 'classic' training programs, including in the context of muscle deconditioning prevention or rehabilitation. An acute LV application (one bout of 20-60 min) may be considered as a significant neuromuscular workload, as demonstrated by an impairment of force generating capacity and LV-induced neural changes. Accordingly, it has been reported that a training period of LV is efficient in improving muscular performance over a wide range of training (duration, number of session) and vibration (frequency, amplitude, site of application) parameters. The functional improvements are principally triggered by adaptations within the central nervous system. A model illustrating the current research on LV-induced adaptations is provided.
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Imai R, Osumi M, Ishigaki T, Morioka S. The influence of trait anxiety and illusory kinesthesia on pain threshold. J Phys Ther Sci 2017; 29:1236-1241. [PMID: 28744055 PMCID: PMC5509599 DOI: 10.1589/jpts.29.1236] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2017] [Accepted: 04/27/2017] [Indexed: 12/12/2022] Open
Abstract
[Purpose] It has also been reported that decreased activity in the reward pathway causes
a decrease in brain activity in the descending pain control system in people with high
trait anxiety. Activation of this system is dependent on both the reward pathway and motor
areas. Recently, studies have also shown that motor areas are activated by illusory
kinesthesia. It was aimed to explore whether anxiety trait modulates the influence of
illusory kinesthesia on pain threshold. [Subjects and Methods] The pain threshold and
trait anxiety at rest before vibratory tendon stimulation (the task) were measured. After
the task, the pain threshold, the illusory kinesthesia angle, and the intensity of
illusory kinesthesia for patients with and without illusory kinesthesia were measured. A
total of 35 healthy right-handed students participated, among whom 22 and 13 were included
in the illusion and no-illusion groups, respectively. [Results] There was a significant
increase in the pain threshold after task completion in both groups; however, there was no
statistically significant difference between the two groups. Correlational analysis
revealed that State-Trait Anxiety Inventory-trait score correlated negatively with the
pain threshold in the no-illusion group, but there was no correlation in the illusion
group. [Conclusion] The pain threshold improved regardless of the size of trait anxiety in
the illusion group, but did not improve merely through sensory input by vibratory
stimulation in the no-illusion group. Thus, illusory kinesthesia has effect of increasing
the pain threshold.
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Affiliation(s)
- Ryota Imai
- Department of Neurorehabilitation, Graduate School of Health Science, Kio University, Japan.,Department of Rehabilitation, Kawachi General Hospital, Japan
| | | | - Tomoya Ishigaki
- Department of Neurorehabilitation, Graduate School of Health Science, Kio University, Japan
| | - Shu Morioka
- Department of Neurorehabilitation, Graduate School of Health Science, Kio University, Japan.,Neuro Rehabilitation Research Center, Kio University, Japan
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Saito A, Ando R, Akima H. Effects of prolonged vibration to vastus intermedius muscle on force steadiness of knee extensor muscles during isometric force-matching task. J Electromyogr Kinesiol 2016; 31:48-54. [PMID: 27668572 DOI: 10.1016/j.jelekin.2016.09.002] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2016] [Revised: 09/06/2016] [Accepted: 09/16/2016] [Indexed: 11/15/2022] Open
Abstract
Afferent inputs from Ia fibers in muscle spindles are essential for the control of force and prolonged vibration has been applied to muscle-tendon units to manipulate the synaptic input from Ia afferents onto α-motor neurons. The vastus intermedius (VI) reportedly provides the highest contribution to the low-level knee extension torque among the individual synergists of quadriceps femoris (QF). The purpose of the present study was to examine the effect of prolonged vibration to the VI on force steadiness of the QF. Nine healthy men (25.1±4.3years) performed submaximal force-matching task of isometric knee extension for 15s before and after mechanical vibration to the superficial region of VI for 30min. Target forces were 2.5%, 10%, and 30% of maximal voluntary contraction (MVC), and force steadiness was determined by the coefficient of variation (CV) of force. After the prolonged VI vibration, the CV of force at 2.5%MVC was significantly increased, but CVs at 10% and 30%MVCs were not significantly changed. The present study concluded that application of prolonged vibration to the VI increased force fluctuations of the QF during a very low-level force-matching task.
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Affiliation(s)
- Akira Saito
- Faculty of Sport Sciences, Waseda University, 2-579-15 Mikajima, Tokorozawa, Saitama, Japan.
| | - Ryosuke Ando
- Graduate School of Education and Human Development, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan; Japan Society for the Promotion of Science, 5-3-1 Kojimachi, Chiyoda-ku, Tokyo, Japan
| | - Hiroshi Akima
- Graduate School of Education and Human Development, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan; Research Center of Health, Physical Fitness & Sports, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi, Japan
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Saito A, Ando R, Akima H. Effects of prolonged patellar tendon vibration on force steadiness in quadriceps femoris during force-matching task. Exp Brain Res 2015; 234:209-17. [DOI: 10.1007/s00221-015-4447-x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2015] [Accepted: 09/16/2015] [Indexed: 11/25/2022]
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The acute effects of spinal manipulation on neuromuscular function in asymptomatic individuals: A preliminary study. Phys Ther Sport 2015; 16:121-6. [DOI: 10.1016/j.ptsp.2014.06.004] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2013] [Revised: 05/13/2014] [Accepted: 06/12/2014] [Indexed: 11/16/2022]
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Oscillations in motor unit discharge are reflected in the low-frequency component of rectified surface EMG and the rate of change in force. Exp Brain Res 2013; 231:267-76. [PMID: 24002673 DOI: 10.1007/s00221-013-3689-8] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2013] [Accepted: 08/22/2013] [Indexed: 10/26/2022]
Abstract
Common drive to a motor unit (MU) pool manifests as low-frequency oscillations in MU discharge rate, producing fluctuations in muscle force. The aim of the study was to examine the temporal correlation between instantaneous MU discharge rate and rectified EMG in low frequencies. Additionally, we attempted to examine whether there is a temporal correlation between the low-frequency oscillations in MU discharge rate and the first derivative of force (dF/dt). Healthy young subjects produced steady submaximal force with their right finger as a single task or while maintaining a pinch-grip force with the left hand as a dual task. Surface EMG and fine-wire MU potentials were recorded from the first dorsal interosseous muscle in the right hand. Surface EMG was band-pass filtered (5-1,000 Hz) and full-wave rectified. Rectified surface EMG and the instantaneous discharge rate of MUs were smoothed by a Hann-window of 400 ms duration (equivalent to 2 Hz low-pass filtering). In each of the identified MUs, the smoothed MU discharge rate was positively correlated with the rectified-and-smoothed EMG as confirmed by the distinct peak in cross-correlation function with greater values in the dual task compared with the single task. Additionally, the smoothed MU discharge rate was temporally correlated with dF/dt more than with force and with rectified-and-smoothed EMG. The results indicated that the low-frequency component of rectified surface EMG and the first derivative of force provide temporal information on the low-frequency oscillations in the MU discharge rate.
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Lucy Hatton A, Dixon J, Rome K, Martin D. Effect of foot orthoses on lower limb muscle activation: a critical review. PHYSICAL THERAPY REVIEWS 2013. [DOI: 10.1179/174328808x252037] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
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Chow JW, Stokic DS. Impaired force steadiness is associated with changes in force frequency composition in subacute stroke. Neuroscience 2013; 242:69-77. [PMID: 23548515 DOI: 10.1016/j.neuroscience.2013.03.040] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2013] [Revised: 03/14/2013] [Accepted: 03/22/2013] [Indexed: 12/01/2022]
Abstract
We tested the hypothesis that impaired force steadiness early after stroke is associated with changes in frequency composition of the force signal during constant-force task. The power spectra and the relationship between power spectra and force variability during isometric knee extension (10%, 20%, 30%, and 50% of peak torque for 10s) were studied in the paretic and non-paretic legs of 34 stroke patients (64±14years, 8-25days post-injury) and the dominant leg of 20 controls (62±10years). Power spectrum analysis of the force signal included the median frequency, peak power frequency, relative peak power, and relative power in 0-3, 4-6, and 8-12Hz bands. Force variability, quantified by coefficient of variation (CV), was increased in patients at 3 of the 4 contraction levels (P⩽0.001). Median frequency across all force levels was decreased and the relative peak power was increased in the paretic and non-paretic legs compared to controls (P⩽0.001). The relative power was increased in 0-3Hz band and decreased in both 4-6 and 8-12Hz bands in the paretic leg only (P⩽0.001). Progressively stronger contractions brought about a significant decrease in relative power in the 0-3Hz band and increase in 8-12Hz band in controls but not in stroke subjects. The hypothesis was confirmed by significant non-linear correlations between CV and each relative spectral power found in the paretic leg at most contraction levels (0.22⩽R(2)⩽0.72, P⩽0.0004) and in the non-paretic leg at 10% only (0.35⩽R(2)⩽0.52, P⩽0.0002), but not in controls. Fugl-Meyer lower extremity motor and sensory scores were not related to the frequency measures in stroke subjects (P>0.05). Limited modulation of frequency spectra and the emergence of non-linear relation between power spectra and force variability suggest that less broadband force output may account in part for impaired force steadiness in paretic and non-paretic legs early after stroke.
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Affiliation(s)
- J W Chow
- Center for Neuroscience and Neurological Recovery, Methodist Rehabilitation Center, Jackson, MS 39216, USA.
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Yoshitake Y, Shinohara M. Low-frequency component of rectified EMG is temporally correlated with force and instantaneous rate of force fluctuations during steady contractions. Muscle Nerve 2013; 47:577-84. [DOI: 10.1002/mus.23628] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/12/2012] [Indexed: 11/08/2022]
Affiliation(s)
- Yasuhide Yoshitake
- Department of Sports and Life Sciences; National Institute of Fitness and Sports in Kanoya; 1 Shiromizu; Kanoya; Kagoshima; 8912393; Japan
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Eye-hand synergy and intermittent behaviors during target-directed tracking with visual and non-visual information. PLoS One 2012; 7:e51417. [PMID: 23236498 PMCID: PMC3517518 DOI: 10.1371/journal.pone.0051417] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2012] [Accepted: 10/31/2012] [Indexed: 11/19/2022] Open
Abstract
Visual feedback and non-visual information play different roles in tracking of an external target. This study explored the respective roles of the visual and non-visual information in eleven healthy volunteers who coupled the manual cursor to a rhythmically moving target of 0.5 Hz under three sensorimotor conditions: eye-alone tracking (EA), eye-hand tracking with visual feedback of manual outputs (EH tracking), and the same tracking without such feedback (EHM tracking). Tracking error, kinematic variables, and movement intermittency (saccade and speed pulse) were contrasted among tracking conditions. The results showed that EHM tracking exhibited larger pursuit gain, less tracking error, and less movement intermittency for the ocular plant than EA tracking. With the vision of manual cursor, EH tracking achieved superior tracking congruency of the ocular and manual effectors with smaller movement intermittency than EHM tracking, except that the rate precision of manual action was similar for both types of tracking. The present study demonstrated that visibility of manual consequences altered mutual relationships between movement intermittency and tracking error. The speed pulse metrics of manual output were linked to ocular tracking error, and saccade events were time-locked to the positional error of manual tracking during EH tracking. In conclusion, peripheral non-visual information is critical to smooth pursuit characteristics and rate control of rhythmic manual tracking. Visual information adds to eye-hand synchrony, underlying improved amplitude control and elaborate error interpretation during oculo-manual tracking.
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Zanca GG, Saccol MF, Oliveira AB, Mattiello SM. Shoulder internal and external rotations torque steadiness in overhead athletes with and without impingement symptoms. J Sci Med Sport 2012; 16:433-7. [PMID: 23088897 DOI: 10.1016/j.jsams.2012.09.004] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2012] [Revised: 08/23/2012] [Accepted: 09/21/2012] [Indexed: 11/25/2022]
Abstract
OBJECTIVES This study aimed to investigate torque steadiness of shoulder internal and external rotations in regularly training overhead athletes with and without impingement symptoms. DESIGN Cross-sectional laboratory study. METHODS Three groups were evaluated: athletes with impingement symptoms (n=21), asymptomatic athletes (n=25) and non-athletes (n=21). To assess torque steadiness, the participants performed 3 submaximal contractions (35% of peak torque) for 10s each, with the arm at 90° of shoulder abduction and 90° of external rotation. The standard deviation, coefficient of variation, mean exerted torque and time to stability were measured from the steadiness trials. RESULTS The standard deviation of internal rotation was higher in asymptomatic athletes than in non-athletes (p<0.01); however, there was no difference between the athletes with impingement symptoms and the other groups. The other variables presented no differences among the groups. CONCLUSIONS Higher torque fluctuation of shoulder internal rotation in asymptomatic athletes may point to neuromuscular adaptations related to throwing training. However, the steadiness patterns of athletes with impingement symptoms did not differ from those of asymptomatic athletes or non-athletes.
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Affiliation(s)
- Gisele G Zanca
- Department of Physical Therapy, Federal University of São Carlos, Rodovia Washington Luis, km 235, Postal Code: 13565-905, São Carlos, SP, Brazil
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Oshita K, Yano S. Association of Force Steadiness of Plantar Flexor Muscles and Postural Sway during Quiet Standing by Young Adults. Percept Mot Skills 2012; 115:143-52. [DOI: 10.2466/15.26.29.pms.115.4.143-152] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
This study was conducted to assess the relations of force fluctuations during isometric plantar-flexion and postural sway during quiet standing. Twelve healthy men ( M age = 21 yr., SD = 1) performed unilateral plantar flexion measured by a strain gauge force transducer. Participants performed force-matching tasks; sustained plantar flexion for 20 sec. at levels corresponding to 10% and 20% of maximum voluntary contraction with the visual feedback. Also, participants were asked to stand quietly with their eyes open, and then the center of mass displacement and velocity in the anteroposterior were measured. In analysis, postural sway was associated with force fluctuation at only 10% of maximum voluntary contraction. The statistically significant correlation between variables was found only at corresponding contraction intensities for plantar-flexor muscles. From this one may infer neural strategies in plantar-flexor muscles during quiet standing may be characteristics similar to those controlling the plantar-flexion force in young adults.
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Affiliation(s)
- Kazushige Oshita
- Department of Sports Science, Faculty of Sports Science, Kyushu Kyoritsu University, Graduate School of Human, Development and Environment, Kobe University
| | - Sumio Yano
- Graduate School of Human, Development and Environment, Kobe University
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Lapole T, Deroussen F, Pérot C, Petitjean M. Acute effects of Achilles tendon vibration on soleus and tibialis anterior spinal and cortical excitability. Appl Physiol Nutr Metab 2012; 37:657-63. [DOI: 10.1139/h2012-032] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Prolonged vibration is known to alter muscle performance. Attenuation of Ia afferent efficacy is the main mechanism suggested. However, changes in motor cortex excitability could also be hypothesized. The purpose of the present study was therefore to analyze the acute and outlasting effects of 1 h of Achilles tendon vibration (frequency, 50 Hz) on the soleus (SOL) and tibialis anterior (TA) neuromuscular excitability. Spinal excitability was investigated by means of H-reflexes and F-waves while cortical excitability was characterized by motor evoked potentials (MEPs) obtained by transcranial magnetic stimulation. Twelve subjects performed the experimental procedures 3 times: at the beginning of the testing session (PRE), immediately after 1 h of Achilles tendon vibration (POST), and 1 h after the end of vibration (POST-1H). Prolonged vibration led to acute reduced H-reflex amplitudes for SOL only (46.9% ± 7.7% vs. 32.8% ± 7%; p = 0.006). Mainly presynaptic inhibition mechanisms were thought to be involved because of unchanged F-wave persistence and amplitude mean values, suggesting unaffected motoneuronal excitability. While no acute effects were reported for SOL and TA cortical excitability, both muscles were characterized by an outlasting increase in their MEP amplitude (0.64 ± 0.2 mV vs. 0.43 ± 0.18 mV and 2.17 ± 0.56 mV vs. 1.26 ± 0.36 mV, respectively; p < 0.05). The high modulation of Ia afferent input by vibration led to changes in motor cortex excitability that could contribute to the enhancement in muscular activation capacities reported after chronic use of tendon vibration.
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Affiliation(s)
- Thomas Lapole
- EA 3300 Adaptations Physiologiques à l’Exercice et Réadaptation à l’Effort, UFR STAPS Amiens, Université de Picardie Jules Verne, Amiens, France
- Université de Technologie, Compiègne CNRS UMR 7338, Biomécanique et Bioingénierie, F-60205 Compiègne CEDEX, France
| | - François Deroussen
- Service de Chirurgie Orthopédique Pédiatrique, Centre Hospitalier Universitaire d’Amiens, France
| | - Chantal Pérot
- Université de Technologie, Compiègne CNRS UMR 7338, Biomécanique et Bioingénierie, F-60205 Compiègne CEDEX, France
| | - Michel Petitjean
- EA 2931 Centre de Recherche sur le Sport et le Mouvement, Université Paris Ouest, Nanterre, France
- Service d’Explorations Fonctionnelles du Système Nerveux, Centre Hospitalier Universitaire d’Amiens, France
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Salomoni SE, Graven-Nielsen T. Experimental muscle pain increases normalized variability of multidirectional forces during isometric contractions. Eur J Appl Physiol 2012; 112:3607-17. [PMID: 22331280 DOI: 10.1007/s00421-012-2343-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/17/2011] [Accepted: 01/31/2012] [Indexed: 10/28/2022]
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USHIYAMA JUNICHI, MASANI KEI. Relation between Postural Stability and Plantar Flexors Muscle Volume in Young Males. Med Sci Sports Exerc 2011; 43:2089-94. [DOI: 10.1249/mss.0b013e31821e512d] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Krishnan C, Allen EJ, Williams GN. Effect of knee position on quadriceps muscle force steadiness and activation strategies. Muscle Nerve 2011; 43:563-73. [PMID: 21404288 DOI: 10.1002/mus.21981] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
INTRODUCTION In this study we investigated the effect of knee position on quadriceps force steadiness and activation strategies. METHODS Quadriceps force steadiness was evaluated in 22 volunteers at two knee positions by testing their ability to regulate submaximal force. Muscle activation strategies were studied in both time and frequency domains using surface electromyography. RESULTS Quadriceps force fluctuations and the associated agonist and antagonist activity were significantly higher at 90° than at 30° of flexion (P < 0.05). The quadriceps median frequency recorded at 30° was significantly higher than at 90° of flexion (P < 0.05). Regression analyses revealed that force steadiness was related to quadriceps activation and median frequency (P < 0.001), but not to hamstring coactivation (P > 0.05). CONCLUSIONS The results indicate that knee position significantly affects quadriceps force steadiness and activation strategies. This finding may have important implications for designing a force control testing protocol and interpreting test results.
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Affiliation(s)
- Chandramouli Krishnan
- Searle Laboratory, Sensory Motor Performance Program, Rehabilitation Institute of Chicago, Chicago, Illinois, USA.
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Oshita K, Yano S. Low-frequency Force Steadiness Practice in Plantar Flexor Muscle Reduces Postural Sway during Quiet Standing. J Physiol Anthropol 2011; 30:233-9. [DOI: 10.2114/jpa2.30.233] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
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Reduced force steadiness in women with neck pain and the effect of short term vibration. J Electromyogr Kinesiol 2010; 21:283-90. [PMID: 21195628 DOI: 10.1016/j.jelekin.2010.11.011] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2010] [Revised: 11/02/2010] [Accepted: 11/29/2010] [Indexed: 11/21/2022] Open
Abstract
This study compares neck force steadiness in women with neck pain and controls and the way this is influenced by short term vibration of the neck. In the first experiment, 9 women with chronic neck pain and 9 controls performed 10-s isometric cervical flexion at 15N. Intramuscular EMG was recorded from the sternocleidomastoid muscle. In the second experiment, 10 women with neck pain and 10 controls performed 10-s isometric cervical flexion at 25% of their maximal force before and after vibration to the neck (bursts of 50Hz with duration 20, 40, 60 and 120s). Surface EMG was acquired from the sternocleidomastoid and splenius capitis. In both experiments, force steadiness was characterized by the coefficient of variation (CoV) and the relative power in three frequency subbands (low: 0-3Hz; middle: 4-6Hz; high: 8-12Hz) of the force signal. Women with neck pain exhibited decreased force steadiness (Exp 1: patients 3.9±1.3%, controls 2.7±0.9%, P<0.05; Exp 2: patients 3.4±1.2%, controls 1.7±0.6%, P<0.01) which was associated with higher power in the low-frequency band (patients 71.2±9.6%, controls 56.7±9.2%, P<0.01). Following vibration, CoV (2.6±1.1%, P<0.05) and the power in the low-frequency band of the force signal decreased (63.1±13.9%, P<0.05) in the patient group. These effects were not present in controls. Motor unit behavior and surface EMG amplitude were similar between groups. In conclusion, women with neck pain have reduced force steadiness, likely due to alterations in Ia afferent input. Vibration, which modulates Ia afferent input, increases force steadiness in patients with neck pain.
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Brazaitis M, Skurvydas A, Vadopalas K, Daniusevičiūtė L. Force variability depends on core and muscle temperature. J Therm Biol 2010. [DOI: 10.1016/j.jtherbio.2010.08.002] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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Kouzaki M, Shinohara M. Steadiness in plantar flexor muscles and its relation to postural sway in young and elderly adults. Muscle Nerve 2010; 42:78-87. [PMID: 20544908 DOI: 10.1002/mus.21599] [Citation(s) in RCA: 97] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
To investigate the functional significance of force fluctuations during voluntary contraction with a select muscle group, we examined the association between force fluctuations during voluntary contraction with plantar flexor muscles and postural sway during quiet standing in 20 young and 20 elderly adults. Young and elderly subjects maintained a quiet standing position on a force platform. They also performed a force-matching task with unilateral isometric plantar flexion. A positive correlation was found in young and elderly adults between the coefficient of variation (CV) of center of pressure during quiet standing and the CV of force during plantar flexion only at contraction intensities of < or =5% maximum voluntary contraction that corresponded to muscle activity during quiet standing. The electromyogram power in the medial gastrocnemius was greater in the elderly than in young adults by approximately 10 Hz during quiet standing and at low contraction intensities during plantar flexion. Fluctuations in motor output during low-intensity plantar flexion were associated with postural sway during quiet standing in both young and elderly adults.
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Affiliation(s)
- Motoki Kouzaki
- Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Sakyo-ku, Kyoto 606-8501, Japan.
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Missenard O, Mottet D, Perrey S. Factors responsible for force steadiness impairment with fatigue. Muscle Nerve 2009; 40:1019-32. [PMID: 19623631 DOI: 10.1002/mus.21331] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
In this study we investigated the contribution of muscle activation to the impairment of fine force control with fatigue. In three experiments, we manipulated muscle activation and measured force variability before and after a fatigue protocol. When muscle activation was left free (subjects had to match the same absolute force pre- and post-fatigue), fatigue increased muscle activation at moderate force levels only, and force variability increased regardless of the level of force. When muscle activation was controlled (subjects had to match the same electromyographic activity), fatigue no longer increased force variability, except at low force levels. When voluntary muscle activation was suppressed (muscles were electrically stimulated), force variability was unaffected by fatigue. We conclude that the impairment of force steadiness with fatigue is mainly due to the increase in muscle activation at moderate forces, but there are other central sources of force fluctuation present at low force levels.
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Affiliation(s)
- Olivier Missenard
- Motor Efficiency and Deficiency Laboratory, University Montpellier 1, EA 2991, 700 Avenue du Pic Saint Loup, 34090 Montpellier, France
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Tracy BL. Visuomotor contribution to force variability in the plantarflexor and dorsiflexor muscles. Hum Mov Sci 2007; 26:796-807. [PMID: 17765988 PMCID: PMC2148254 DOI: 10.1016/j.humov.2007.07.001] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2006] [Revised: 06/25/2007] [Accepted: 07/10/2007] [Indexed: 11/28/2022]
Abstract
The visual correction employed during isometric contractions of large proximal muscles contributes variability to the descending command and alters fluctuations in muscle force. This study explored the contribution of visuomotor correction to isometric force fluctuations for the more distal dorsiflexor (DF) and plantarflexor (PF) muscles of the ankle. Twenty-one healthy adults performed steady isometric contractions with the DF and PF muscles both with (VIS) and without (NOVIS) visual feedback of the force. The target forces exerted ranged from 2.5% to 80% MVC. The standard deviation (SD) and coefficient of variation (CV) of force was measured from the detrended (drift removed) VIS and NOVIS steadiness trials. Removal of VIS reduced the CV of force by 19% overall. The reduction in fluctuations without VIS was significant across a large range of target forces and was more consistent for the PF than the DF muscles. Thus, visuomotor correction contributes to the variability of force during isometric contractions of the ankle dorsiflexors and plantarflexors.
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Affiliation(s)
- Brian L Tracy
- Department of Health and Exercise Science, 220 Moby-B Complex, Colorado State University, Fort Collins, CO 80523-1582, USA.
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Clark BC, Pierce JR, Manini TM, Ploutz-Snyder LL. Effect of prolonged unweighting of human skeletal muscle on neuromotor force control. Eur J Appl Physiol 2007; 100:53-62. [PMID: 17287986 DOI: 10.1007/s00421-007-0399-6] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/10/2007] [Indexed: 12/20/2022]
Abstract
The purpose of this study was to determine the effect of 4 weeks of unilateral lower limb suspension (ULLS) on the fluctuations in motor output and the associated physiological changes. Subjects (n = 17) performed steady isometric plantarflexion (PF) and knee extension (KE) tasks, and KE shortening and lengthening contractions (intensity = 25% maximum). Spinal excitability of the soleus muscle was assessed via the H-reflex, muscle cross-sectional area (CSA) via MRI, along with EMG activity during the PF tasks. Following ULLS, isometric force fluctuations increased approximately 12% for the PF, and 22% for the KE (P < 0.05), with no difference in the pattern of PF muscle activation (P = 0.46). The unsteadiness of lengthening KE contractions increased 25% following ULLS (P = 0.03), while KE steadiness during shortening contractions was not altered (P = 0.98). Significant correlations were observed between the percent changes in PF isometric force fluctuations and H-reflex (r = 0.49, P = 0.04), and between the PF isometric force fluctuations and PF CSA (r = -0.61, P < 0.01). These findings suggest the effects of unweighting on neuromotor performance are muscle group and contraction type dependent, and that the disuse-paradigm altering muscle CSA and spinal excitability may serve to mediate the associated loss of steadiness.
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Affiliation(s)
- Brian C Clark
- Interdisciplinary Institute for Neuromusculoskeletal Research, Department of Biomedical Sciences, Ohio University College of Osteopathic Medicine, 211 Irvine Hall, Athens, OH 45701, USA.
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Yoshitake Y, Kouzaki M, Fukuoka H, Fukunaga T, Shinohara M. Modulation of muscle activity and force fluctuations in the plantarflexors after bedrest depends on knee position. Muscle Nerve 2007; 35:745-55. [PMID: 17366590 DOI: 10.1002/mus.20764] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Force fluctuations in leg muscles increase after bedrest, perhaps due to modulation of the neural strategy that is specific to a muscle or common to agonist muscles. The purpose of this study was to examine the modulation of muscle activity and force fluctuations during steady contractions with variable involvement of plantarflexor muscles after bedrest at knee-flexed (FLX) and extended (EXT) positions. Before and after 20-day bedrest, plantarflexion force and surface electromyogram (EMG) in the medial gastrocnemius (MG), lateral gastrocnemius, and soleus muscles were measured during steady isometric contractions in five young men. In EXT, power <or=10 HZ in the rectified EMG of MG increased significantly after bedrest. This low-frequency modulation of muscle activity in MG accompanied a 29% increase in the standard deviation of force. There was no change in EMG in other muscles. In FLX, there was no adjustment in EMG or force fluctuations. These results suggest that low-frequency modulation of MG plays a role in increasing force fluctuations during steady plantarflexion in EXT after bedrest. The findings indicate task/muscle specificity in the modulation of neural strategy during steady contractions after bedrest and underscore the importance of designing a specific training regimen targeted to particular tasks/muscles with regard to force fluctuations in multiple-agonist systems.
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Affiliation(s)
- Yasuhide Yoshitake
- Department of Health Sciences, Oita University of Nursing and Health Sciences, Oita, Japan
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Tracy BL, Mehoudar PD, Ortega JD. The amplitude of force variability is correlated in the knee extensor and elbow flexor muscles. Exp Brain Res 2006; 176:448-64. [PMID: 16896977 DOI: 10.1007/s00221-006-0631-3] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2006] [Accepted: 07/06/2006] [Indexed: 10/24/2022]
Abstract
The purpose of this study was to determine motor output variability for different muscles in the same individuals. Ten young (21.7 +/- 3.4 years) and ten elderly (72.1 +/- 3.9 years) men underwent assessment of maximal isometric (MVC) and dynamic (1-RM) strength, and performed constant-force (2-50% MVC), constant-load (5-50% 1-RM load), and unloaded postural contractions as steadily as possible with the first dorsal interosseus (FDI), elbow flexors (EF), and knee extensors (KE). The coefficient of variation (CV) of force for isometric contractions and the standard deviation (SD) of acceleration for concentric, eccentric, and postural contractions were calculated. The 1-RM load, the CV of force for four of five isometric target forces, and the SD of acceleration during postural contractions were correlated between the EF and KE muscles. MVC force, 1-RM load, and SD of acceleration during postural contractions were not correlated between the FDI/EF or FDI/KE. The CV of force was correlated between the FDI/EF and FDI/KE for two of five isometric target forces. The SD of acceleration during concentric and eccentric contractions was not correlated between muscles. The normalized fluctuations during isometric contractions were greater for the FDI compared with the EF and KE. Elderly adults displayed greater fluctuations only for the FDI during low-force isometric and postural contractions. The dominant frequency of fluctuations was similar for the EF and KE muscles. The correlated fluctuations for the EF and KE muscles, within subjects, suggests that the two motor neuron pools transform the various neural inputs similarly.
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Affiliation(s)
- Brian L Tracy
- Department of Health and Exercise Science, Colorado State University, 220 Moby-B Complex, Fort Collins, CO 80523-1582, USA.
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Mottram CJ, Maluf KS, Stephenson JL, Anderson MK, Enoka RM. Prolonged Vibration of the Biceps Brachii Tendon Reduces Time to Failure When Maintaining Arm Position With a Submaximal Load. J Neurophysiol 2006; 95:1185-93. [PMID: 16282200 DOI: 10.1152/jn.00807.2005] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Vibration reduces the amplitudes of the tendon jerk response and the Hoffmann and stretch reflexes in the muscle exposed to the vibration, yet does not alter the time to task failure when the task involves exerting a submaximal force against a rigid restraint. Because the amplitude of the stretch reflex is greater when a limb acts against a compliant load than a rigid restraint, the purpose was to determine the influence of prolonged tendon vibration on the time to failure when maintaining limb position with the elbow flexor muscles. Twenty-five healthy men performed the fatiguing contraction by maintaining elbow angle at 1.57 rad until failure while supporting a load equal to 20% of maximal voluntary contraction (MVC) force. The fatiguing contraction was performed on 3 separate days with different levels of vibration applied to the biceps brachii tendon: no vibration, subthreshold for a tonic vibration reflex (TVR), and suprathreshold for a TVR. MVC force before the fatiguing contraction was similar across the three sessions (mean of 3 sessions: 313 ± 54 N, P = 0.83). Despite a similar decline in MVC force after the fatiguing contraction across conditions (–18.0 ± 8.0%, P > 0.05), the time to task failure was 3.7 ± 1.4 min for the suprathreshold TVR condition, 4.3 ± 2.1 min for the subthreshold TVR condition, and 5.0 ± 2.2 min for the no-vibration condition ( P < 0 0.001). The average EMG of the elbow flexor muscles was similar ( P = 0.22) during the fatiguing contractions. However, the fluctuations in limb acceleration at task onset were greater for the suprathreshold TVR condition ( P < 0.01), but were not different between the subthreshold TVR and no-vibration conditions ( P ≥ 0.22). Furthermore, the difference in the SD of limb acceleration between the no-vibration and vibration conditions was correlated with the difference in time to failure for the no-vibration and subthreshold TVR conditions ( P = 0.03; r2 = 0.22), but not for the no-vibration and suprathreshold TVR conditions ( P = 0.90; r2 = 0.001). These findings indicate that prolonged vibration reduced the time to failure of a sustained contraction when subjects maintained limb position, suggesting that peripheral inputs to the motor neuron pool play a significant role in sustaining a contraction during tasks that require active control of limb position.
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Affiliation(s)
- Carol J Mottram
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA
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Abstract
Excitatory input to the alpha motor neuron pool from Ia afferents is enhanced by brief vibration, yet is depressed when vibration is applied for prolonged periods. The purpose of this article is to synthesize recent findings from several studies on the effects of prolonged vibration on motor unit activity and motor performance during maximal and submaximal contractions in humans. Prolonged vibration does not alter voluntary drive during maximal contractions, but it does reduce Ia afferent input to alpha motor neuron pools and discharge rate of motor units in the vibrated muscles, leading to a reduction in maximal voluntary contraction force. Alterations in the activity of the motor unit pool may be variable across synergistic muscles due to potential neural connections between synergistic muscles. Prolonged vibration reduces the force fluctuations during submaximal steady contractions, presumably due to a depression of group Ia feedback from leg muscles. When prolonged vibration evokes a tonic vibration reflex in a hand muscle, the mean discharge rate of motor units during a submaximal force-matching contraction increases, leading to an increase in the associated force fluctuations. In summary, prolonged vibration modulates Ia feedback and motor unit activity, which leads to reduced peak force during maximal contractions and altered force fluctuations during submaximal contractions.
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Affiliation(s)
- Minoru Shinohara
- Department of Integrative Physiology, University of Colorado, Boulder, CO 80309-0354, USA.
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Shinohara M, Yoshitake Y, Kouzaki M, Fukunaga T. The medial gastrocnemius muscle attenuates force fluctuations during plantar flexion. Exp Brain Res 2005; 169:15-23. [PMID: 16193274 DOI: 10.1007/s00221-005-0119-6] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2005] [Accepted: 06/15/2005] [Indexed: 11/30/2022]
Abstract
Force fluctuations during steady contractions of multiple agonist muscles may be influenced by the relative contribution of force by each muscle. The purpose of the study was to compare force fluctuations during steady contractions performed with the plantar flexor muscles in different knee positions. Nine men (25.8+/-5.1 years) performed steady contractions of the plantar flexor muscles in the knee-flexed and knee-extended (greater involvement of the gastrocnemii muscles) positions. The maximal voluntary contraction (MVC) force was 32% greater in the knee-extended position compared with the knee-flexed position. The target forces were 2.5-10% MVC force in the respective position. The amplitude of electromyogram in the medial gastrocnemius muscle was greater in the knee-extended position (10.50+/-9.80%) compared with the knee-flexed position (1.26+/-1.15%, P<0.01). The amplitude of electromyogram in the soleus muscle was not influenced by the knee position. The amplitude of electromyogram in the lateral gastrocnemius and tibialis anterior muscles was marginal and unaltered with knee position. At the same force (in Newtons), the standard deviation of force was lower in the knee-extended position compared with the knee-flexed position. These results indicate that force fluctuations during plantar flexion are attenuated with greater involvement of the medial gastrocnemius muscle.
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Affiliation(s)
- Minoru Shinohara
- Department of Integrative Physiology, University of Colorado, Clare Room 114, 354 UCB, Boulder, 80309-0354, USA.
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Shinohara M, Moritz CT, Pascoe MA, Enoka RM. Prolonged muscle vibration increases stretch reflex amplitude, motor unit discharge rate, and force fluctuations in a hand muscle. J Appl Physiol (1985) 2005; 99:1835-42. [PMID: 16024525 DOI: 10.1152/japplphysiol.00312.2005] [Citation(s) in RCA: 52] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to compare the influence of prolonged vibration of a hand muscle on the amplitude of the stretch reflex, motor unit discharge rate, and force fluctuations during steady, submaximal contractions. Thirty-two young adults performed 10 isometric contractions at a constant force (5.0 +/- 2.3% of maximal force) with the first dorsal interosseus muscle. Each contraction was held steady for 10 s, and then stretch reflexes were evoked. Subsequently, 20 subjects had vibration applied to the relaxed muscle for 30 min, and 12 subjects received no vibration. The muscle vibration induced a tonic vibration reflex. The intervention (vibration or no vibration) was followed by 2 sets of 10 constant-force contractions with applied stretches (After and Recovery trials). The mean electromyogram amplitude of the short-latency component of the stretch reflex increased by 33% during the After trials (P < 0.01) and by 38% during the Recovery trials (P < 0.01). The standard deviation of force during the steady contractions increased by 21% during the After trials (P < 0.05) and by 28% during the Recovery trials (P < 0.01). The discharge rate of motor units increased from 10.3 +/- 2.7 pulses/s (pps) before vibration to 12.2 +/- 3.1 pps (P < 0.01) during the After trials and to 11.9 +/- 2.6 pps during the Recovery trials (P < 0.01). There was no change in force fluctuations or stretch reflex magnitude for the subjects in the Control group. The results indicate that prolonged vibration increased the short-latency component of the stretch reflex, the discharge rate of motor units, and the fluctuations in force during contractions by a hand muscle. These adjustments were necessary to achieve the target force due to the vibration-induced decrease in the force capacity of the muscle.
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Affiliation(s)
- Minoru Shinohara
- Dept. of Integrative Physiology, Univ. of Colorado, Boulder, CO 80309-0354, USA.
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