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Amiridis IG, Kannas T, Sahinis C, Negro F, Trypidakis G, Kellis E, Enoka RM. More Variability in Tibialis Anterior Function during the Adduction of the Foot than Dorsiflexion of the Ankle. Med Sci Sports Exerc 2024; 56:851-859. [PMID: 38190382 DOI: 10.1249/mss.0000000000003377] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2024]
Abstract
INTRODUCTION The aim of the study was to compare maximal force, force steadiness, and the discharge characteristics of motor units in the tibialis anterior (TA) muscle during submaximal isometric contractions for ankle dorsiflexion and adduction of the foot. METHODS Nineteen active young adults performed maximal and submaximal isometric dorsiflexion and adduction contractions at five target forces (5%, 10%, 20%, 40%, and 60% maximal voluntary contraction [MVC]). The activity of motor units in TA was recorded by high-density EMG. RESULTS The maximal force was similar between dorsiflexion and adduction, despite EMG amplitude for TA being greater ( P < 0.05) during dorsiflexion than adduction. Τhe coefficient of variation (CV) for force (force steadiness) during dorsiflexion was always less ( P < 0.05) than during adduction, except of 5% MVC force. No differences were observed for mean discharge rate; however, the regression between the changes in discharge rate relative to the change of force was significant for dorsiflexion ( R2 = 0.25, P < 0.05) but not for adduction. Discharge variability, however, was usually less during dorsiflexion. The CV for interspike interval was less ( P < 0.05) at 10%, 20%, and 40% MVC but greater at 60% MVC during dorsiflexion than adduction. Similarly, the SD values of the filtered cumulative spike train of the motor units in TA were less ( P < 0.05) at 5%, 10%, 20%, and 40% MVC during dorsiflexion than adduction. CONCLUSIONS Although the mean discharge rate of motor units in TA was similar during foot adduction and ankle dorsiflexion, discharge variability was less during dorsiflexion resulting in less accurate performance of the steady adduction contractions. The neural drive to bifunctional muscles differs during their accessory function, which must be considered for training and rehabilitation interventions.
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Affiliation(s)
- Ioannis G Amiridis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Theodoros Kannas
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Chrysostomos Sahinis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Francesco Negro
- Department of Clinical and Experimental Sciences, University of Brescia, Brescia, ITALY
| | - Georgios Trypidakis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Eleftherios Kellis
- Department of Physical Education and Sport Sciences at Serres, Aristotle University of Thessaloniki, Serres, GREECE
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, CO
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Hanson MR, Swanson CW, Whittier TT, Fling BW. Inhibitory signaling as a predictor of leg force control in young and older adults. Exp Brain Res 2022; 240:1005-1016. [PMID: 35171308 DOI: 10.1007/s00221-022-06321-x] [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: 11/08/2021] [Accepted: 01/29/2022] [Indexed: 11/04/2022]
Abstract
As the populations of the United States and developed nations age, motor control performance is adversely impacted, resulting in functional impairments that can diminish quality of life. Generally, force control in the lower limb worsens with age, with older adults (OA) displaying more variable and less accurate submaximal forces. Corticospinal inhibitory signaling may influence force control, with those OA who maintain corticospinal inhibitory signaling capacity achieving steadier forces. This study aimed to assess the relationships between lower limb force control and transcranial magnetic stimulation (TMS) measures of corticospinal inhibition (i.e., cortical silent period (cSP) duration and depth). 15 OA and 14 young adults (YA) were recruited for this study. All subjects underwent a TMS protocol to elicit the cSP while maintaining 15% of their maximal force in their knee extensor muscles. OA and YA did not display differences in force control metrics or corticospinal inhibitory measures. However, in OA, maximal cSP depth (%dSP max) was associated with lower force variability. No other significant relationships existed in the YA or OA groups. Future studies will benefit from evaluating a range of target forces and target muscles to assess potential relationships between sensorimotor inhibitory capacity and control of muscle force output.
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Affiliation(s)
- Moriah R Hanson
- Department of Occupational Therapy, Colorado State University, Fort Collins, CO, USA
| | - Clayton W Swanson
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA
| | - Tyler T Whittier
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA
| | - Brett W Fling
- Department of Health & Exercise Science, Colorado State University, 1582 Campus Delivery, Moby B-201A, Fort Collins, CO, 80523, USA. .,Molecular, Cellular, and Integrative Neuroscience Program, Colorado State University, Fort Collins, CO, USA.
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Henderson TT, Thorstensen JR, Morrison S, Tucker MG, Kavanagh JJ. Physiological tremor is suppressed and force steadiness is enhanced with increased availability of serotonin regardless of muscle fatigue. J Neurophysiol 2022; 127:27-37. [PMID: 34851768 DOI: 10.1152/jn.00403.2021] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Although there is evidence that 5-HT acts as an excitatory neuromodulator to enhance maximal force generation, it is largely unknown how 5-HT activity influences the ability to sustain a constant force during steady-state contractions. A total of 22 healthy individuals participated in the study, where elbow flexion force was assessed during brief isometric contractions at 10% maximal voluntary contraction (MVC), 60% MVC, MVC, and during a sustained MVC. The selective serotonin reuptake inhibitor, paroxetine, suppressed physiological tremor and increased force steadiness when performing the isometric contractions. In particular, a main effect of drug was detected for peak power of force within the 8-12 Hz range (P = 0.004) and the coefficient of variation (CV) of force (P < 0.001). A second experiment was performed where intermittent isometric elbow flexions (20% MVC sustained for 2 min) were repeatedly performed so that serotonergic effects on physiological tremor and force steadiness could be assessed during the development of fatigue. Main effects of drug were once again detected for peak power of force in the 8-12 Hz range (P = 0.002) and CV of force (P = 0.003), where paroxetine suppressed physiological tremor and increased force steadiness when the elbow flexors were fatigued. The findings of this study suggest that enhanced availability of 5-HT in humans has a profound influence of maintaining constant force during steady-state contractions. The action of 5-HT appears to suppress fluctuations in force regardless of the fatigue state of the muscle.NEW & NOTEWORTHY Converging lines of research indicate that enhanced serotonin availability increases maximal force generation. However, it is largely unknown how serotonin influences the ability to sustain a constant force. We performed two experiments to assess physiological tremor and force steadiness in unfatigued and fatigued muscle when serotonin availability was enhanced in the central nervous system. Enhanced availability of serotonin reduced physiological tremor amplitude and improved steadiness regardless of muscle fatigue.
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Affiliation(s)
- T T Henderson
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
| | - J R Thorstensen
- Child Health Research Centre, The University of Queensland, Brisbane, Queensland, Australia
| | - S Morrison
- School of Rehabilitation Sciences, Old Dominion University, Norfolk, Virginia
| | - M G Tucker
- Barwon Health, University Hospital Geelong, Melbourne, Victoria, Australia
| | - J J Kavanagh
- Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, Australia
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Loh SK, Lim JZ, Pan JW, Aziz L, Lee M, Kong PW. Air pistol shooting: upper limb muscle activation between training and simulated competition. Sports Biomech 2021:1-12. [PMID: 34542383 DOI: 10.1080/14763141.2021.1975812] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/03/2021] [Accepted: 08/28/2021] [Indexed: 10/20/2022]
Abstract
Heightened stress during air pistol competitions may impair shooters' abilities to maintain gun stability, resulting in inferior performance. This study aimed to compare the pre-trigger muscle activation levels of upper muscles in 10-m air pistol shooters between training and simulated competition conditions. Seven sub-elite shooters from the Singapore National Youth Air Pistol Team shot 30 shots in a training versus simulated competition condition in randomised orders on separate days. Muscle activation for the forearm and shoulder muscles, namely extensor carpi radialis, flexor carpi ulnaris, anterior deltoid, and posterior deltoid, were recorded using electromyography (EMG). Shooting performance was evaluated by total shot scores. Stress level was monitored via heart rate and the Mental Readiness Form-3. No statistically significant differences were found in EMG, performance, or stress-related variables between conditions, although moderate-to-large effect sizes were observed in some muscle activation and self-reported stress indicators. Analysis of individual performances using smallest worthwhile change showed that two participants improved under the simulated competition condition, while two declined, and three remained unaffected. In conclusion, sub-elite youth air pistol shooters were able to exhibit good neuromuscular control under high anxiety situations and thus their performance was largely unaffected.
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Affiliation(s)
- Suan K Loh
- Physical Education and Sports Science Academic Group, National Institute of Education, Nanyang Technological University, Singapore, Singapore
| | - Jolene Z Lim
- Physical Education and Sports Science Academic Group, National Institute of Education, Nanyang Technological University, Singapore, Singapore
| | - Jing Wen Pan
- Physical Education and Sports Science Academic Group, National Institute of Education, Nanyang Technological University, Singapore, Singapore
| | | | - Marcus Lee
- Sports Biomechanics, Singapore Sports Institute, Singapore, Singapore
| | - Pui W Kong
- Physical Education and Sports Science Academic Group, National Institute of Education, Nanyang Technological University, Singapore, Singapore
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Enoka RM, Farina D. Force Steadiness: From Motor Units to Voluntary Actions. Physiology (Bethesda) 2021; 36:114-130. [DOI: 10.1152/physiol.00027.2020] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Voluntary actions are controlled by the synaptic inputs that are shared by pools of spinal motor neurons. The slow common oscillations in the discharge times of motor units due to these synaptic inputs are strongly correlated with the fluctuations in force during submaximal isometric contractions (force steadiness) and moderately associated with performance scores on some tests of motor function. However, there are key gaps in knowledge that limit the interpretation of differences in force steadiness.
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Affiliation(s)
- Roger M. Enoka
- Department of Integrative Physiology, University of Colorado Boulder, Colorado
| | - Dario Farina
- Department of Bioengineering, Faculty of Engineering, Imperial College London, London, United Kingdom
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Davis LA, Alenazy MS, Almuklass AM, Feeney DF, Vieira T, Botter A, Enoka RM. Force control during submaximal isometric contractions is associated with walking performance in persons with multiple sclerosis. J Neurophysiol 2020; 123:2191-2200. [PMID: 32347151 DOI: 10.1152/jn.00085.2020] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023] Open
Abstract
Individuals with multiple sclerosis (MS) experience progressive declines in movement capabilities, especially walking performance. The purpose of our study was to compare the amount of variance in walking performance that could be explained by the functional capabilities of lower leg muscles in persons with MS and a sex- and age-matched control group. Participants performed two walking tests (6-min walk and 25-ft walk), strength tests for the plantar flexor and dorsiflexor muscles, and steady submaximal (10% and 20% maximum) isometric contractions. High-density electromyography (EMG) was recorded during the steady contractions, and the signals were decomposed to identify the discharge times of concurrently active motor units. There were significant differences between the two groups in the force fluctuations during the steady contractions (force steadiness), the strength of the plantar flexor and dorsiflexor muscles, and the discharge characteristics during the steady contractions. Performance on the two walking tests by the MS group was moderately associated with force steadiness of the plantar flexor and dorsiflexor muscles; worse force steadiness was associated with poorer walking performance. In contrast, the performance of the control group was associated with muscle strength (25-ft test) and force steadiness of the dorsiflexors and variance in common input of motor units to the plantar flexors (6-min test). These findings indicate that a reduction in the ability to maintain a steady force during submaximal isometric contractions is moderately associated with walking performance of persons with MS.NEW & NOTEWORTHY The variance in walking endurance and walking speed was associated with force control of the lower leg muscles during submaximal isometric contractions in individuals with multiple sclerosis (MS). In contrast, the fast walking speed of a sex- and age-matched control group was associated with the strength of lower leg muscles. These findings indicate that moderate declines in the walking performance of persons with MS are more associated with impairments in force control rather than decreases in muscle strength.
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Affiliation(s)
- Leah A Davis
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Mohammed S Alenazy
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Awad M Almuklass
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Daniel F Feeney
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Taian Vieira
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Alberto Botter
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
| | - Roger M Enoka
- Department of Integrative Physiology University of Colorado, Boulder, Colorado
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Ahmar NE, Ueda J, Shinohara M. Anti-phase cocontraction practice attenuates in-phase low-frequency oscillations between antagonistic muscles as assessed with phase coherence. Exp Brain Res 2019; 238:63-72. [PMID: 31781822 DOI: 10.1007/s00221-019-05700-1] [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: 07/11/2019] [Accepted: 11/22/2019] [Indexed: 10/25/2022]
Abstract
Voluntary contraction of skeletal muscles involves common in-phase neural oscillations in low frequencies (around 1-2 Hz) across muscles. The purpose of this study was to determine if anti-phase antagonistic cocontraction practice can attenuate the occurrence of in-phase low-frequency oscillations in antagonistic muscle activity. For this purpose, we determined the probability density function of phase coherence in surface electromyogram (EMG) between antagonistic muscles. Healthy young adults were assigned to one of three intervention groups. They performed an isometric transient and steady cocontraction test with elbow flexors and extensors before and after a session of distinct intervention. In the Cocontraction group, subjects practiced alternating anti-phase isometric cocontraction with the flexors and extensors concurrently. In the Contraction group, subjects practiced alternating isometric contraction levels with flexors or extensors independently. Subjects in the Control group did not perform motor practice. The occurrence of in-phase coherence < 3 Hz during the cocontraction test (including transient and steady portions) was determined from the probability density function of phase coherence in rectified EMG between pairs of elbow flexor and extensor muscles. The change in the probability of in-phase coherence after the intervention period was greatest in the Cocontraction group, followed by Contraction group, and then Control group, on average. The Cocontraction group showed significantly greater reductions than the Control group across the cocontraction test portions. The results suggest that a session of anti-phase cocontraction practice can consistently attenuate the occurrence of in-phase low-frequency oscillations between cocontracting antagonistic muscles across steady and non-steady cocontractions in healthy young adults.
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Affiliation(s)
- Nayef E Ahmar
- School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Jun Ueda
- George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, Atlanta, GA, 30332, USA
| | - Minoru Shinohara
- School of Biological Sciences, Georgia Institute of Technology, 555 14th Street NW, Atlanta, GA, 30332-0356, USA.
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Walker S, Avela J, Wikgren J, Meeusen R, Piitulainen H, Baker SN, Parviainen TM. Aging and Strength Training Influence Knee Extensor Intermuscular Coherence During Low- and High-Force Isometric Contractions. Front Physiol 2019; 9:1933. [PMID: 30728782 PMCID: PMC6351450 DOI: 10.3389/fphys.2018.01933] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2018] [Accepted: 12/21/2018] [Indexed: 12/11/2022] Open
Abstract
Aging is associated with reduced maximum force production and force steadiness during low-force tasks, but both can be improved by training. Intermuscular coherence measures coupling between two peripheral surface electromyography (EMG) signals in the frequency domain. It is thought to represent the presence of common input to alpha-motoneurons, but the functional meaning of intermuscular coherence, particularly regarding aging and training, remain unclear. This study investigated knee extensor intermuscular coherence in previously sedentary young (18–30 years) and older (67–73 years) subjects before and after a 14-week strength training intervention. YOUNG and OLDER groups performed maximum unilateral isometric knee extensions [100% maximum voluntary contraction (MVC)], as well as force steadiness tests at 20 and 70% MVC, pre- and post-training. Intermuscular (i.e., EMG-EMG) coherence analyses were performed for all (three) contraction intensities in vastus lateralis and medialis muscles. Pre-training coefficient of force variation (i.e., force steadiness) and MVC (i.e., maximum torque) were similar between groups. Both groups improved MVC through training, but YOUNG improved more than OLDER (42 ± 27 Nm versus 18 ± 16 Nm, P = 0.022). Force steadiness did not change during 20% MVC trials in either group, but YOUNG demonstrated increased coefficient of force variation during 70% MVC trials (1.28 ± 0.46 to 1.57 ± 0.70, P = 0.01). YOUNG demonstrated greater pre-training coherence during 20% and 70% MVC trials, particularly within the 8–14 Hz (e.g., 20%: 0.105 ± 0.119 versus 0.016 ± 0.009, P = 0.001) and 16–30 Hz (20%: 0.063 ± 0.078 versus 0.012 ± 0.007, P = 0.002) bands, but not during 100% MVC trials. Strength training led to increases in intermuscular coherence within the 40–60 Hz band during 70% MVC trials in YOUNG only, while OLDER decreased within the 8–14 Hz band during 100% MVC trials. Age-related differences in intermuscular coherence were observed between young and older individuals, even when neuromuscular performance levels were similar. The functional significance of intermuscular coherence remains unclear, since coherence within different frequency bands did not explain any of the variance in the regression models for maximum strength or force steadiness during 20 and 70% MVC trials.
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Affiliation(s)
- Simon Walker
- Neuromuscular Research Center, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Janne Avela
- Neuromuscular Research Center, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland
| | - Jan Wikgren
- Department of Psychology, Centre for Interdisciplinary Brain Research, Faculty of Education and Psychology, University of Jyväskylä, Jyväskylä, Finland
| | - Romain Meeusen
- Human Physiology Research Group, Vrije Universiteit Brussel, Brussels, Belgium
| | - Harri Piitulainen
- Neuromuscular Research Center, Faculty of Sport and Health Sciences, University of Jyväskylä, Jyväskylä, Finland.,Department of Neuroscience and Biomedical Engineering, Aalto University, Espoo, Finland
| | - Stuart N Baker
- Institute of Neuroscience, Medical School, Newcastle University, Newcastle upon Tyne, United Kingdom
| | - Tiina M Parviainen
- Department of Psychology, Centre for Interdisciplinary Brain Research, Faculty of Education and Psychology, University of Jyväskylä, Jyväskylä, Finland
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Mani D, Almuklass AM, Hamilton LD, Vieira TM, Botter A, Enoka RM. Motor unit activity, force steadiness, and perceived fatigability are correlated with mobility in older adults. J Neurophysiol 2018; 120:1988-1997. [PMID: 30044670 DOI: 10.1152/jn.00192.2018] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
The purpose of our study was to examine the associations between the performance of older adults on four tests of mobility and the physical capabilities of the lower leg muscles. The assessments included measures of muscle strength, muscle activation, and perceived fatigability. Muscle activation was quantified as the force fluctuations-a measure of force steadiness-and motor unit discharge characteristics of lower leg muscles during submaximal isometric contractions. Perceived fatigability was measured as the rating of perceived exertion achieved during a test of walking endurance. Twenty participants (73 ± 4 yr) completed one to four evaluation sessions that were separated by at least 3 wk. The protocol included a 400-m walk, a 10-m walk at maximal and preferred speeds, a chair-rise test, and the strength, force steadiness, and discharge characteristics of motor units detected by high-density electromyography of lower leg muscles. Multiple-regression analyses yielded statistically significant models that explained modest amounts of the variance in the four mobility tests. The variance explained by the regression models was 39% for 400-m walk time, 33% for maximal walk time, 42% for preferred walk time, and 27% for chair-rise time. The findings indicate that differences in mobility among healthy older adults were partially associated with the level of perceived fatigability (willingness of individuals to exert themselves) achieved during the test of walking endurance and the discharge characteristics of soleus, medial gastrocnemius, and tibialis anterior motor units during steady submaximal contractions with the plantar flexor and dorsiflexor muscles. NEW & NOTEWORTHY Differences among healthy older adults in walking endurance, walking speed, and ability to rise from a chair can be partially explained by the performance capabilities of lower leg muscles. Assessments comprised the willingness to exert effort (perceived fatigability) and the discharge times of action potentials by motor units in calf muscles during submaximal isometric contractions. These findings indicate that the nervous system contributes significantly to differences in mobility among healthy older adults.
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Affiliation(s)
- Diba Mani
- Department of Integrative Physiology, University of Colorado , Boulder, Colorado
| | - Awad M Almuklass
- Department of Integrative Physiology, University of Colorado , Boulder, Colorado.,College of Medicine, King Saud bin Abdulaziz University for Health Sciences , Riyadh , Saudi Arabia
| | - Landon D Hamilton
- Department of Integrative Physiology, University of Colorado , Boulder, Colorado
| | - Taian M Vieira
- LISiN, Department of Electronics and Telecommunications, Politecnico di Torino, Turin , Italy
| | - Alberto Botter
- LISiN, Department of Electronics and Telecommunications, Politecnico di Torino, Turin , Italy
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado , Boulder, Colorado
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Relationship between Joint Position Sense, Force Sense, and Muscle Strength and the Impact of Gymnastic Training on Proprioception. BIOMED RESEARCH INTERNATIONAL 2018; 2018:5353242. [PMID: 29670901 PMCID: PMC5835294 DOI: 10.1155/2018/5353242] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2017] [Revised: 01/09/2018] [Accepted: 01/18/2018] [Indexed: 11/23/2022]
Abstract
The aims of this study were (1) to assess the relationship between joint position (JPS) and force sense (FS) and muscle strength (MS) and (2) to evaluate the impact of long-term gymnastic training on particular proprioception aspects and their correlations. 17 elite adult gymnasts and 24 untrained, matched controls performed an active reproduction (AR) and passive reproduction (PR) task and a force reproduction (FR) task at the elbow joint. Intergroup differences and the relationship between JPS, FS, and MS were evaluated. While there was no difference in AR or PR between groups, absolute error in the control group was higher during the PR task (7.15 ± 2.72°) than during the AR task (3.1 ± 1.93°). Mean relative error in the control group was 61% higher in the elbow extensors than in the elbow flexors during 50% FR, while the gymnast group had similar results in both reciprocal muscles. There was no linear correlation between JPS and FS in either group; however, FR was negatively correlated with antagonist MS. In conclusion, this study found no evidence for a relationship between the accuracy of FS and JPS at the elbow joint. Long-term gymnastic training improves the JPS and FS of the elbow extensors.
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Ahmar NE, Shinohara M. Slow Intermuscular Oscillations are Associated with Cocontraction Steadiness. Med Sci Sports Exerc 2017; 49:1955-1964. [PMID: 28422771 DOI: 10.1249/mss.0000000000001302] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
PURPOSE Voluntary muscle contraction often involves low-frequency correlated neural oscillations across muscles, which may degrade steady cocontraction between antagonistic muscles with distinct levels of activation per each muscle (unbalanced cocontraction). The purposes of the study were 1) to determine whether there is an association between the low-frequency correlated EMG oscillations and the performance of steady unbalanced cocontraction across individuals and 2) to determine whether a bout of out-of-phase cocontraction practice reduces the in-phase low-frequency correlated neural oscillations and improves the performance of steady unbalanced cocontraction. METHODS Healthy young adults were divided into three intervention groups: cocontraction, contraction, and control. All participants were tested for unbalanced steady cocontractions with antagonistic muscles about the elbow joint before and after a bout of intervention with the visual feedback of surface EMG. During the intervention period, the cocontraction group practiced an out-of-phase cocontraction, whereas the contraction group practiced agonist contractions. RESULTS Mean squared error and variance of EMG amplitude were positively correlated with low-frequency EMG coherence <3 Hz across subjects, which became more prevalent after the intervention period. There was no specific effect of the cocontraction intervention on these variables. CONCLUSION These findings suggest that individuals with less low-frequency correlated neural oscillations tend to perform steady cocontraction more skillfully, and the low-frequency correlated oscillations may not be acutely modulated by one bout of out-of-phase cocontraction practice.
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Affiliation(s)
- Nayef E Ahmar
- 1School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA; and 2School of Biological Sciences, Georgia Institute of Technology, Atlanta, GA
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Santos GL, García-Salazar LF, Souza MB, Oliveira AB, Camargo PR, Russo TL. Torque steadiness and muscle activation are bilaterally impaired during shoulder abduction and flexion in chronic post-stroke subjects. J Electromyogr Kinesiol 2016; 30:151-60. [PMID: 27451360 DOI: 10.1016/j.jelekin.2016.07.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2016] [Revised: 06/30/2016] [Accepted: 07/05/2016] [Indexed: 01/05/2023] Open
Abstract
OBJECTIVE To characterize sensorimotor control and muscle activation in the shoulder of chronic hemiparetic during abduction and flexion in maximal and submaximal isometric contractions. Furthermore, to correlate submaximal sensorimotor control with motor impairment and degree of shoulder subluxation. METHODS Thirteen chronic hemiparetic post-stroke age-gender matched with healthy were included. Isometric torques were assessed using a dynamometer. Electromyographic activity of the anterior and middle deltoid, upper trapezius, pectoralis major and serratus anterior muscles were collected. Variables were calculated for torque: peak, time to target, standard deviation (SD), coefficient of variation (CV), and standard error (RMSE); for muscle activity: maximum and minimum values, range and coefficient of activation. Motor impairment was determined by Fugl-Meyer and shoulder subluxation was measured with a caliper. RESULTS Paretic and non-paretic limbs reduced peak and muscle activation during maximal isometric contraction. Paretic limb generated lower force when compared with non-paretic and control. Paretic and non-paretic presented higher values of SD, CV, RMSE, and CV for prime mover muscles and minimum values for all muscles during steadiness. No correlation was found between sensorimotor control, motor impairment and shoulder subluxation. CONCLUSION Chronic hemiparetic presented bilateral deficits in sensorimotor and muscle control during maximal and submaximal shoulder abduction and flexion.
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Affiliation(s)
- Gabriela Lopes Santos
- Department of Physiotherapy, Federal University of São Carlos (UFSCar), São Carlos, SP, Brazil.
| | - Luisa Fernanda García-Salazar
- Department of Physiotherapy, Federal University of São Carlos (UFSCar), São Carlos, SP, Brazil; Physical Therapy Program, School of Medicine and Health Science, University of Rosario, Bogotá, D.C., Colombia
| | - Matheus Bragança Souza
- Department of Physiotherapy, Federal University of São Carlos (UFSCar), São Carlos, SP, Brazil
| | - Ana Beatriz Oliveira
- Department of Physiotherapy, Federal University of São Carlos (UFSCar), São Carlos, SP, Brazil
| | - Paula Rezende Camargo
- Department of Physiotherapy, Federal University of São Carlos (UFSCar), São Carlos, SP, Brazil
| | - Thiago Luiz Russo
- Department of Physiotherapy, Federal University of São Carlos (UFSCar), São Carlos, SP, Brazil
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Arellano CJ, Caha D, Hennessey JE, Amiridis IG, Baudry S, Enoka RM. Fatigue-induced adjustment in antagonist coactivation by old adults during a steadiness task. J Appl Physiol (1985) 2016; 120:1039-46. [PMID: 26846553 DOI: 10.1152/japplphysiol.00908.2015] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2015] [Accepted: 01/22/2016] [Indexed: 11/22/2022] Open
Abstract
The purpose of this study was to determine the adjustments in the level of coactivation during a steadiness task performed by young and old adults after the torque-generating capacity of the antagonist muscles was reduced by a fatiguing contraction. Torque steadiness (coefficient of variation) and electromyographic activity of the extensor and flexor carpi radialis muscles were measured as participants matched a wrist extensor target torque (10% maximum) before and after sustaining an isometric contraction (30% maximum) with wrist flexors to task failure. Time to failure was similar (P = 0.631) for young (417 ± 121 s) and old (452 ± 174 s) adults. The reduction in maximal voluntary contraction torque (%initial) for the wrist flexors after the fatiguing contraction was greater (P = 0.006) for young (32.5 ± 13.7%) than old (21.8 ± 6.6%) adults. Moreover, maximal voluntary contraction torque for the wrist extensors declined for old (-13.7 ± 12.7%; P = 0.030), but not young (-5.4 ± 13.8%; P = 0.167), adults. Torque steadiness during the matching task with the wrist extensors was similar before and after the fatiguing contraction for both groups, but the level of coactivation increased after the fatiguing contraction for old (P = 0.049) but not young (P = 0.137) adults and was twice the amplitude for old adults (P = 0.002). These data reveal that old adults are able to adjust the amount of antagonist muscle activity independent of the agonist muscle during steady submaximal contractions.
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Affiliation(s)
- Christopher J Arellano
- Department of Ecology and Evolutionary Biology, Brown University, Providence, Rhode Island; Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - David Caha
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - Joseph E Hennessey
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
| | - Ioannis G Amiridis
- Department of Physical Education and Sport Sciences, Aristotle University of Thessaloniki, Serres, Greece; and
| | - Stéphane Baudry
- Laboratory of Applied Biology, Neurosciences Institute, Université Libre de Bruxelles, Brussels, Belgium
| | - Roger M Enoka
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado
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Koyama S, Tanabe S, Takeda K, Sakurai H, Kanada Y. Modulation of spinal inhibitory reflexes depends on the frequency of transcutaneous electrical nerve stimulation in spastic stroke survivors. Somatosens Mot Res 2016; 33:8-15. [PMID: 26949041 DOI: 10.3109/08990220.2016.1142436] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
Neurophysiological studies in healthy subjects suggest that increased spinal inhibitory reflexes from the tibialis anterior (TA) muscle to the soleus (SOL) muscle might contribute to decreased spasticity. While 50 Hz is an effective frequency for transcutaneous electrical nerve stimulation (TENS) in healthy subjects, in stroke survivors, the effects of TENS on spinal reflex circuits and its appropriate frequency are not well known. We examined the effects of different frequencies of TENS on spinal inhibitory reflexes from the TA to SOL muscle in stroke survivors. Twenty chronic stroke survivors with ankle plantar flexor spasticity received 50-, 100-, or 200-Hz TENS over the deep peroneal nerve (DPN) of the affected lower limb for 30 min. Before and immediately after TENS, reciprocal Ia inhibition (RI) and presynaptic inhibition of the SOL alpha motor neuron (D1 inhibition) were assessed by adjusting the unconditioned H-reflex amplitude. Furthermore, during TENS, the time courses of spinal excitability and spinal inhibitory reflexes were assessed via the H-reflex, RI, and D1 inhibition. None of the TENS protocols affected mean RI, whereas D1 inhibition improved significantly following 200-Hz TENS. In a time-series comparison during TENS, repeated stimulation did not produce significant changes in the H-reflex, RI, or D1 inhibition regardless of frequency. These results suggest that the frequency-dependent effect of TENS on spinal reflexes only becomes apparent when RI and D1 inhibition are measured by adjusting the amplitude of the unconditioned H-reflex. However, 200-Hz TENS led to plasticity of synaptic transmission from the antagonist to spastic muscles in stroke survivors.
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Affiliation(s)
- Soichiro Koyama
- a Department of Rehabilitation , Kawamura Hospital , Gifu , Japan ;,b Faculty of Rehabilitation, School of Health Sciences, Fujita Health University , >Aichi > , Japan
| | - Shigeo Tanabe
- b Faculty of Rehabilitation, School of Health Sciences, Fujita Health University , >Aichi > , Japan
| | - Kazuya Takeda
- a Department of Rehabilitation , Kawamura Hospital , Gifu , Japan
| | - Hiroaki Sakurai
- b Faculty of Rehabilitation, School of Health Sciences, Fujita Health University , >Aichi > , Japan
| | - Yoshikiyo Kanada
- b Faculty of Rehabilitation, School of Health Sciences, Fujita Health University , >Aichi > , Japan
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Dideriksen JL, Negro F, Farina D. The optimal neural strategy for a stable motor task requires a compromise between level of muscle cocontraction and synaptic gain of afferent feedback. J Neurophysiol 2015. [PMID: 26203102 DOI: 10.1152/jn.00247.2015] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Increasing joint stiffness by cocontraction of antagonist muscles and compensatory reflexes are neural strategies to minimize the impact of unexpected perturbations on movement. Combining these strategies, however, may compromise steadiness, as elements of the afferent input to motor pools innervating antagonist muscles are inherently negatively correlated. Consequently, a high afferent gain and active contractions of both muscles may imply negatively correlated neural drives to the muscles and thus an unstable limb position. This hypothesis was systematically explored with a novel computational model of the peripheral nervous system and the mechanics of one limb. Two populations of motor neurons received synaptic input from descending drive, spinal interneurons, and afferent feedback. Muscle force, simulated based on motor unit activity, determined limb movement that gave rise to afferent feedback from muscle spindles and Golgi tendon organs. The results indicated that optimal steadiness was achieved with low synaptic gain of the afferent feedback. High afferent gains during cocontraction implied increased levels of common drive in the motor neuron outputs, which were negatively correlated across the two populations, constraining instability of the limb. Increasing the force acting on the joint and the afferent gain both effectively minimized the impact of an external perturbation, and suboptimal adjustment of the afferent gain could be compensated by muscle cocontraction. These observations show that selection of the strategy for a given contraction implies a compromise between steadiness and effectiveness of compensations to perturbations. This indicates that a task-dependent selection of neural strategy for steadiness is necessary when acting in different environments.
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Affiliation(s)
- Jakob L Dideriksen
- Center for Sensory-Motor Interaction (SMI), Department of Health Science and Technology, Aalborg University, Aalborg, Denmark; and Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
| | - Francesco Negro
- Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
| | - Dario Farina
- Department of Neurorehabilitation Engineering, Bernstein Focus Neurotechnology Göttingen, Bernstein Center for Computational Neuroscience, University Medical Center Göttingen, Georg-August University, Göttingen, Germany
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