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Hajj-Boutros G, Sonjak V, Faust A, Hedge E, Mastrandrea C, Lagacé JC, St-Martin P, Naz Divsalar D, Sadeghian F, Chevalier S, Liu-Ambrose T, Blaber AP, Dionne IJ, Duchesne S, Hughson R, Kontulainen S, Theou O, Morais JA. Impact of 14 Days of Bed Rest in Older Adults and an Exercise Countermeasure on Body Composition, Muscle Strength, and Cardiovascular Function: Canadian Space Agency Standard Measures. Gerontology 2023; 69:1284-1294. [PMID: 37717560 PMCID: PMC10634275 DOI: 10.1159/000534063] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2023] [Accepted: 09/01/2023] [Indexed: 09/19/2023] Open
Abstract
INTRODUCTION Head-down bed rest (HDBR) has long been used as an analog to microgravity, and it also enables studying the changes occurring with aging. Exercise is the most effective countermeasure for the deleterious effects of inactivity. The aim of this study was to investigate the efficacy of an exercise countermeasure in healthy older participants on attenuating musculoskeletal deconditioning, cardiovascular fitness level, and muscle strength during 14 days of HDBR as part of the standard measures of the Canadian Space Agency. METHODS Twenty-three participants (12 males and 11 females), aged 55-65 years, were admitted for a 26-day inpatient stay at the McGill University Health Centre. After 5 days of baseline assessment tests, they underwent 14 days of continuous HDBR followed by 7 days of recovery with repeated tests. Participants were randomized to passive physiotherapy or an exercise countermeasure during the HDBR period consisting of 3 sessions per day of either high-intensity interval training (HIIT) or low-intensity cycling or strength exercises for the lower and upper body. Peak aerobic power (V̇O2peak) was determined using indirect calorimetry. Body composition was assessed by dual-energy X-ray absorptiometry, and several muscle group strengths were evaluated using an adjustable chair dynamometer. A vertical jump was used to assess whole-body power output, and a tilt test was used to measure cardiovascular and orthostatic challenges. Additionally, changes in various blood parameters were measured as well as the effects of exercise countermeasure on these measurements. RESULTS There were no differences at baseline in main characteristics between the control and exercise groups. The exercise group maintained V̇O2peak levels similar to baseline, whereas it decreased in the control group following 14 days of HDBR. Body weight significantly decreased in both groups. Total and leg lean masses decreased in both groups. However, total body fat mass decreased only in the exercise group. Isometric and isokinetic knee extension muscle strength were significantly reduced in both groups. Peak velocity, flight height, and flight time were significantly reduced in both groups with HDBR. CONCLUSION In this first Canadian HDBR study in older adults, an exercise countermeasure helped maintain aerobic fitness and lean body mass without affecting the reduction of knee extension strength. However, it was ineffective in protecting against orthostatic intolerance. These results support HIIT as a promising approach to preserve astronaut health and functioning during space missions, and to prevent deconditioning as a result of hospitalization in older adults.
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Affiliation(s)
- Guy Hajj-Boutros
- Research Institute of the McGill University Health Centre, Montréal, Québec, Canada,
| | - Vita Sonjak
- Research Institute of the McGill University Health Centre, Montréal, Québec, Canada
| | - Andréa Faust
- Research Institute of the McGill University Health Centre, Montréal, Québec, Canada
| | - Eric Hedge
- Department of Kinesiology, Schlegel-University of Waterloo Research Institute for Aging, Waterloo, Ontario, Canada
| | - Carmelo Mastrandrea
- Department of Kinesiology and Health Sciences, University of Waterloo, Waterloo, Ontario, Canada
| | - Jean-Christophe Lagacé
- Faculté des Sciences de l'activité Physique, Centre de Recherche sur le Vieillissement, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Philippe St-Martin
- Faculté des Sciences de l'activité Physique, Centre de Recherche sur le Vieillissement, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Donya Naz Divsalar
- Department of Biomedical Physiology and Kinesiology, Aerospace Physiology Laboratory, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Farshid Sadeghian
- Department of Biomedical Physiology and Kinesiology, Aerospace Physiology Laboratory, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Stéphanie Chevalier
- Research Institute of the McGill University Health Centre, Montréal, Québec, Canada
- School of Human Nutrition, McGill University, Montreal, Québec, Canada
| | - Teresa Liu-Ambrose
- Aging, Mobility and Cognitive Neuroscience Laboratory, Department of Physical Therapy, Faculty of Medicine, University of British Columbia, Vancouver, British Columbia, Canada
| | - Andrew P Blaber
- Department of Biomedical Physiology and Kinesiology, Aerospace Physiology Laboratory, Simon Fraser University, Burnaby, British Columbia, Canada
| | - Isabelle J Dionne
- Faculté des Sciences de l'activité Physique, Centre de Recherche sur le Vieillissement, Université de Sherbrooke, Sherbrooke, Québec, Canada
| | - Simon Duchesne
- Department of Radiology and Nuclear Medicine, Université Laval, Quebec City, Québec, Canada
- CERVO Brain Research Center, Quebec City, Québec, Canada
| | - Richard Hughson
- Department of Kinesiology, Schlegel-University of Waterloo Research Institute for Aging, Waterloo, Ontario, Canada
| | - Saija Kontulainen
- College of Kinesiology, University of Saskatchewan, Saskatoon, Saskatchewan, Canada
| | - Olga Theou
- Division of Geriatric Medicine, Queen Elizabeth II Health Sciences Centre, Nova Scotia Health, Halifax, Nova Scotia, Canada
| | - José A Morais
- Research Institute of the McGill University Health Centre, Montréal, Québec, Canada
- Division of Geriatric Medicine, Faculty of Medicine, McGill University, Montreal, Québec, Canada
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Marusic U, Narici M, Simunic B, Pisot R, Ritzmann R. Nonuniform loss of muscle strength and atrophy during bed rest: a systematic review. J Appl Physiol (1985) 2021; 131:194-206. [PMID: 33703945 DOI: 10.1152/japplphysiol.00363.2020] [Citation(s) in RCA: 44] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
Muscle atrophy and decline in muscle strength appear very rapidly with prolonged disuse or mechanical unloading after acute hospitalization or experimental bed rest. The current study analyzed data from short-, medium-, and long-term bed rest (5-120 days) in a pooled sample of 318 healthy adults and modeled the mathematical relationship between muscle strength decline and atrophy. The results show a logarithmic disuse-induced loss of strength and muscle atrophy of the weight-bearing knee extensor muscles. The greatest rate of muscle strength decline and atrophy occurred in the earliest stages of bed rest, plateauing later, and likely contributed to the rapid neuromuscular loss of function in the early period. In addition, during the first 2 wk of bed rest, muscle strength decline is much faster than muscle atrophy: on day 5, the ratio of muscle atrophy to strength decline as a function of bed rest duration is 4.2, falls to 2.4 on day 14, and stabilizes to a value of 1.9 after ∼35 days of bed rest. Positive regression revealed that ∼79% of the muscle strength loss may be explained by muscle atrophy, while the remaining is most likely due to alterations in single fiber mechanical properties, excitation-contraction coupling, fiber architecture, tendon stiffness, muscle denervation, neuromuscular junction damage, and supraspinal changes. Future studies should focus on neural factors as well as muscular factors independent of atrophy (single fiber excitability and mechanical properties, architectural factors) and on the role of extracellular matrix changes. Bed rest results in nonuniform loss of isometric muscle strength and atrophy over time, where the magnitude of change was greater for muscle strength than for atrophy. Future research should focus on the loss of muscle function and the underlying mechanisms, which will aid in the development of countermeasures to mitigate or prevent the decline in neuromuscular efficiency.NEW & NOTEWORTHY Our study contributes to the characterization of muscle loss and weakness processes reflected by a logarithmic decline in muscle strength induced by chronic bed rest. Acute short-term hospitalization (≤5 days) associated with periods of disuse/immobilization/prolonged time in the supine position in the hospital bed is sufficient to significantly decrease muscle mass and size and induce functional changes related to weakness in maximal muscle strength. By bringing together integrated evaluation of muscle structure and function, this work identifies that 79% of the loss in muscle strength can be explained by muscle atrophy, leaving 21% of the functional loss unexplained. The outcomes of this study should be considered in the development of daily countermeasures for preserving neuromuscular integrity as well as preconditioning interventions to be implemented before clinical bed rest or chronic gravitational unloading (e.g., spaceflights).
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Affiliation(s)
- Uros Marusic
- Institute for Kinesiology Research, Science and Research Centre Koper, Koper, Slovenia.,Department of Health Sciences, Alma Mater Europaea-European Center of Maribor, Maribor, Slovenia
| | - Marco Narici
- Institute for Kinesiology Research, Science and Research Centre Koper, Koper, Slovenia.,Department of Biomedical Sciences, University of Padua, Padua, Italy
| | - Bostjan Simunic
- Institute for Kinesiology Research, Science and Research Centre Koper, Koper, Slovenia
| | - Rado Pisot
- Institute for Kinesiology Research, Science and Research Centre Koper, Koper, Slovenia
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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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Winnard A, Scott J, Waters N, Vance M, Caplan N. Effect of Time on Human Muscle Outcomes During Simulated Microgravity Exposure Without Countermeasures-Systematic Review. Front Physiol 2019; 10:1046. [PMID: 31474878 PMCID: PMC6707384 DOI: 10.3389/fphys.2019.01046] [Citation(s) in RCA: 26] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2018] [Accepted: 07/30/2019] [Indexed: 12/11/2022] Open
Abstract
Background: Space Agencies are planning human missions beyond Low Earth Orbit. Consideration of how physiological system adaptation with microgravity (μG) will be managed during these mission scenarios is required. Exercise countermeasures (CM) could be used more sparingly to decrease limited resource costs, including periods of no exercise. This study provides a complete overview of the current evidence, making recommendations on the length of time humans exposed to simulated μG might safely perform no exercise considering muscles only. Methods: Electronic databases were searched for astronaut or space simulation bed rest studies, as the most valid terrestrial simulation, from start of records to July 2017. Studies were assessed with the Quality in Prognostic Studies and bed rest analog studies assessed for transferability to astronauts using the Aerospace Medicine Systematic Review Group Tool for Assessing Bed Rest Methods. Effect sizes, based on no CM groups, were used to assess muscle outcomes over time. Outcomes included were contractile work capacity, muscle cross sectional area, muscle activity, muscle thickness, muscle volume, maximal voluntary contraction force during one repetition maximum, peak power, performance based outcomes, power, and torque/strength. Results: Seventy-five bed rest μG simulation studies were included, many with high risk of confounding factors and participation bias. Most muscle outcomes deteriorated over time with no countermeasures. Moderate effects were apparent by 7-15 days and large by 28-56 days. Moderate effects (>0.6) became apparent in the following order, power and MVC during one repetition maximum (7 days), followed by volume, cross sectional area, torques and strengths, contractile work capacity, thickness and endurance (14 days), then muscle activity (15 days). Large effects (>1.2) became apparent in the following order, volume, cross sectional area (28 days) torques and strengths, thickness (35 days) and peak power (56 days). Conclusions: Moderate effects on a range of muscle parameters may occur within 7-14 days of unloading, with large effects within 35 days. Combined with muscle performance requirements for mission tasks, these data, may support the design of CM programmes to maximize efficiency without compromising crew safety and mission success when incorporated with data from additional physiological systems that also need consideration.
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Affiliation(s)
- Andrew Winnard
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Jonathan Scott
- Space Medicine Office, European Astronaut Centre, Cologne, Germany
| | - Nathan Waters
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Martin Vance
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
| | - Nick Caplan
- Faculty of Health and Life Sciences, Northumbria University, Newcastle upon Tyne, United Kingdom
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Mulavara AP, Peters BT, Miller CA, Kofman IS, Reschke MF, Taylor LC, Lawrence EL, Wood SJ, Laurie SS, Lee SMC, Buxton RE, May-Phillips TR, Stenger MB, Ploutz-Snyder LL, Ryder JW, Feiveson AH, Bloomberg JJ. Physiological and Functional Alterations after Spaceflight and Bed Rest. Med Sci Sports Exerc 2019; 50:1961-1980. [PMID: 29620686 PMCID: PMC6133205 DOI: 10.1249/mss.0000000000001615] [Citation(s) in RCA: 81] [Impact Index Per Article: 16.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/01/2022]
Abstract
Supplemental digital content is available in the text. Introduction Exposure to microgravity causes alterations in multiple physiological systems, potentially impacting the ability of astronauts to perform critical mission tasks. The goal of this study was to determine the effects of spaceflight on functional task performance and to identify the key physiological factors contributing to their deficits. Methods A test battery comprised of seven functional tests and 15 physiological measures was used to investigate the sensorimotor, cardiovascular, and neuromuscular adaptations to spaceflight. Astronauts were tested before and after 6-month spaceflights. Subjects were also tested before and after 70 d of 6° head-down bed rest, a spaceflight analog, to examine the role of axial body unloading on the spaceflight results. These subjects included control and exercise groups to examine the effects of exercise during bed rest. Results Spaceflight subjects showed the greatest decrement in performance during functional tasks that required the greatest demand for dynamic control of postural equilibrium which was paralleled by similar decrements in sensorimotor tests that assessed postural and dynamic gait control. Other changes included reduced lower limb muscle performance and increased HR to maintain blood pressure. Exercise performed during bed rest prevented detrimental change in neuromuscular and cardiovascular function; however, both bed rest groups experienced functional and balance deficits similar to spaceflight subjects. Conclusion Bed rest data indicate that body support unloading experienced during spaceflight contributes to postflight postural control dysfunction. Further, the bed rest results in the exercise group of subjects confirm that resistance and aerobic exercises performed during spaceflight can play an integral role in maintaining neuromuscular and cardiovascular functions, which can help in reducing decrements in functional performance. These results indicate that a countermeasure to mitigate postflight postural control dysfunction is required to maintain functional performance.
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Affiliation(s)
| | | | | | | | | | | | | | - Scott J Wood
- Neurosciences Laboratory, NASA-Johnson Space Center, Houston, TX
| | | | - Stuart M C Lee
- Cardiovascular and Vision Laboratory, KBRwyle, Houston, TX
| | - Roxanne E Buxton
- Exercise Physiology and Countermeasures Laboratory, KBRwyle, Houston, TX
| | | | - Michael B Stenger
- Cardiovascular and Vision Laboratory, NASA-Johnson Space Center, Houston, TX
| | | | - Jeffrey W Ryder
- Exercise Physiology and Countermeasures Laboratory, KBRwyle, Houston, TX
| | - Alan H Feiveson
- Biostatistics Laboratory, NASA-Johnson Space Center, Houston, TX
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Gao Y, Arfat Y, Wang H, Goswami N. Muscle Atrophy Induced by Mechanical Unloading: Mechanisms and Potential Countermeasures. Front Physiol 2018; 9:235. [PMID: 29615929 PMCID: PMC5869217 DOI: 10.3389/fphys.2018.00235] [Citation(s) in RCA: 149] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2017] [Accepted: 03/02/2018] [Indexed: 12/23/2022] Open
Abstract
Prolonged periods of skeletal muscle inactivity or mechanical unloading (bed rest, hindlimb unloading, immobilization, spaceflight and reduced step) can result in a significant loss of musculoskeletal mass, size and strength which ultimately lead to muscle atrophy. With advancement in understanding of the molecular and cellular mechanisms involved in disuse skeletal muscle atrophy, several different signaling pathways have been studied to understand their regulatory role in this process. However, substantial gaps exist in our understanding of the regulatory mechanisms involved, as well as their functional significance. This review aims to update the current state of knowledge and the underlying cellular mechanisms related to skeletal muscle loss during a variety of unloading conditions, both in humans and animals. Recent advancements in understanding of cellular and molecular mechanisms, including IGF1-Akt-mTOR, MuRF1/MAFbx, FOXO, and potential triggers of disuse atrophy, such as calcium overload and ROS overproduction, as well as their role in skeletal muscle protein adaptation to disuse is emphasized. We have also elaborated potential therapeutic countermeasures that have shown promising results in preventing and restoring disuse-induced muscle loss. Finally, identified are the key challenges in this field as well as some future prospectives.
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Affiliation(s)
- Yunfang Gao
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Ministry of Education, Northwest University, Xi'an, China
| | - Yasir Arfat
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Ministry of Education, Northwest University, Xi'an, China
| | - Huiping Wang
- Key Laboratory of Resource Biology and Biotechnology in Western China, College of Life Sciences, Ministry of Education, Northwest University, Xi'an, China
| | - Nandu Goswami
- Physiology Unit, Otto Loewi Center of Research for Vascular Biology, Immunity and Inflammation, Medical University of Graz, Graz, Austria
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Individual difference in β-band corticomuscular coherence and its relation to force steadiness during isometric voluntary ankle dorsiflexion in healthy humans. Clin Neurophysiol 2016; 128:303-311. [PMID: 28042996 DOI: 10.1016/j.clinph.2016.11.025] [Citation(s) in RCA: 23] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Revised: 11/24/2016] [Accepted: 11/26/2016] [Indexed: 11/20/2022]
Abstract
OBJECTIVE Magnitude of β-band coherent neural activities between the sensorimotor cortex and contracting muscle is known to vary across healthy individuals. To clarify how this variance affects actual motor function, this study examined associations between the corticomuscular coherence (CMC) and force steadiness. METHODS CMC was calculated between scalp electroencephalograms (EEGs) over the sensorimotor cortex and surface electromyograms (EMGs) from the tibialis anterior muscle during tonic isometric voluntary ankle dorsiflexion at 30% of maximal effort in 22 healthy individuals. We calculated the maximal peak of CMC (CMCmax), and examined its relations to some measures of force fluctuation, such as the coefficient of variation (ForceCV), the sum of the power spectral density within 1-4Hz (Forceδ-PSD), 5-14Hz (Forceα-PSD), and 15-35Hz (Forceβ-PSD) bands of force signal. RESULTS In all participants showing significant CMC, CMCmax was observed within the β-band. CMCmax was varied across participants (range, 0.084-0.451), and was correlated significantly and positively with ForceCV (r=0.602, p=0.003), Forceβ-PSD (r=0.637, p=0.001), Forceα-PSD (r=0.647, p=0.001), and Forceδ-PSD (r=0.518, p=0.014). CONCLUSION The magnitude of the CMC between EEG over the sensorimotor cortex and EMG of contracting muscle is associated with the amount of force fluctuation during tonic isometric voluntary ankle dorsiflexion in healthy humans. SIGNIFICANCE CMC may influence an individual's ability to stabilize their muscle force output.
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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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Bilateral deficit in maximal force production. Eur J Appl Physiol 2016; 116:2057-2084. [DOI: 10.1007/s00421-016-3458-z] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2016] [Accepted: 08/22/2016] [Indexed: 10/21/2022]
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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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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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A 35-day bed rest does not alter the bilateral deficit of the lower limbs during explosive efforts. Eur J Appl Physiol 2015; 115:1323-30. [DOI: 10.1007/s00421-015-3111-2] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2014] [Accepted: 01/13/2015] [Indexed: 11/27/2022]
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Rejc E, di Prampero PE, Lazzer S, Grassi B, Simunic B, Pisot R, Antonutto G, Narici M. Maximal explosive power of the lower limbs before and after 35 days of bed rest under different diet energy intake. Eur J Appl Physiol 2014; 115:429-36. [PMID: 25344798 DOI: 10.1007/s00421-014-3024-5] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2014] [Accepted: 10/13/2014] [Indexed: 01/10/2023]
Abstract
PURPOSE Microgravity leads to a decline of muscle power especially in the postural muscles of the lower limb. Muscle atrophy primarily contributes to this negative adaptation. Nutritional countermeasures during unloading were shown to possibly mitigate the loss of muscle mass and strength. The aim of this study was to investigate the effects of different diet energy intakes during prolonged inactivity on body composition and lower limbs power output. METHODS The effects of lower or higher diet energy intake on the decline of maximal explosive power of the lower limbs, as determined on a sledge ergometer before and after 35 days of bed rest, were investigated on two matched groups of young healthy volunteers. Body composition and lean volume of the lower limb were also measured. RESULTS After bed rest, fat mass increased (+20.5 %) in the higher energy intake group (N = 9), while it decreased (-4.8 %) in the lower energy intake group (N = 10). Also, the loss of body fat-free mass and lean volume of the lower limb was significantly greater in the higher (-4.6 and -10.8 %, respectively) as compared to the lower (-2.4 and -3.7 %, respectively) diet energy intake group. However, the loss of maximal explosive power was similar between the two groups (-25.2 and -29.5 % in the higher and lower energy intake group, respectively; P = 0.440). CONCLUSIONS The mitigation of loss of muscle mass by means of a moderate caloric diet restriction during prolonged inactivity was not sufficient for reducing the loss of maximal explosive power of the lower limbs.
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Affiliation(s)
- Enrico Rejc
- Department of Medical and Biological Sciences, University of Udine, P.le Kolbe 4, 33100, Udine, Italy,
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Brunner A, Stäuber F, Göhler S, Czepa D, Wendel M, Seuser A, Hilberg T. Impact of joint status on contraction steadiness of m. quadriceps femoris in people with severe haemophilia. Haemophilia 2014; 20:884-90. [DOI: 10.1111/hae.12493] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/06/2014] [Indexed: 12/19/2022]
Affiliation(s)
- A. Brunner
- Department of Sports Medicine; University of Wuppertal; Wuppertal Germany
| | - F. Stäuber
- Department of Sports Medicine; University of Wuppertal; Wuppertal Germany
| | - S. Göhler
- Department of Sports Medicine; University of Wuppertal; Wuppertal Germany
| | - D. Czepa
- Department of Sports Medicine; University of Wuppertal; Wuppertal Germany
| | - M. Wendel
- Institute of Motion Analysis and Quality Control of the Locomotive System; Bonn Germany
| | - A. Seuser
- Institute of Motion Analysis and Quality Control of the Locomotive System; Bonn Germany
| | - T. Hilberg
- Department of Sports Medicine; University of Wuppertal; Wuppertal Germany
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15
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Sarabon N, Rosker J. Effect of 14 days of bed rest in older adults on parameters of the body sway and on the local ankle function. J Electromyogr Kinesiol 2013; 23:1505-11. [PMID: 24099756 DOI: 10.1016/j.jelekin.2013.09.002] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2013] [Revised: 08/19/2013] [Accepted: 09/10/2013] [Indexed: 10/26/2022] Open
Abstract
This study explored the effects of a 14-day horizontal bed rest (BR) without countermeasures on postural sway, maximal voluntary torque and precision of voluntary torque matching. Sixteen subjects were tested before, immediately after and two weeks after BR. The increase in frequency and amplitude after BR was comparable for both sway subcomponents (rambling and trembling) in medial-lateral direction. But in anterior-posterior direction, rambling increased more in frequency (-7% vs. +31%, p < 0.05) while trembling increased more in amplitude (+35% vs. +84%, p < 0.05). The drop in maximal voluntary torque after BR was present for plantar flexion (p < 0.05) but not for dorsal flexion. After the BR, the subjects were less precise in the dorsal flexion torque matching task (p < 0.05). All the observed parameters, except the dorsal flexion torque matching error, returned back to the pre-BR values after the two weeks of re-conditioning. Results of this study indicate that body sway subcomponents responded differently to BR. Based on these findings, it was not possible to draw clear assumptions on the effects of neural and structural changes on body sway.
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Affiliation(s)
- Nejc Sarabon
- University of Primorska, Science and Research Center, Institute for Kinesiology Research, Koper, Slovenia; S2P Ltd., Laboratory for Motor Control and Motor Behaviour, Ljubljana, Slovenia.
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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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17
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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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18
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Cunha FVM, Moura Filho OFD, Moura FS, Martins MDCDCE. Efeito do exercício físico e da administração de testosterona na consolidação de fraturas de tíbia em ratos. FISIOTERAPIA EM MOVIMENTO 2012. [DOI: 10.1590/s0103-51502012000400010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
INTRODUÇÃO: Vários estudos têm sido realizados visando identificar um medicamento que acelere a consolidação de fraturas. OBJETIVO: Avaliar o efeito do exercício físico e da administração de testosterona no processo de consolidação de fratura de tíbia e fíbula de ratos. MATERIAIS E MÉTODOS: Rattus norvegicus (250 a 300 g) foram distribuídos aleatoriamente em quatro grupos de oito animais: Controle- fratura e imobilização; G1- fratura, imobilização e propionato de testosterona; G2- fratura, imobilização e treinamento físico de natação; G3- fratura, imobilização, treinamento físico de natação e propionato de testosterona. Os tratamentos foram iniciados imediatamente após a realização de fraturas fechadas no terço médio da tíbia direita. O programa de treinamento físico consistiu em 50 minutos de natação durante quatro semanas, cinco vezes por semana. O propionato de testosterona 3 mg/kg foi administrado por via subcutânea cinco vezes na semana durante quatro semanas. As variáveis analisadas incluíram evolução ponderal, tamanho do calo ósseo, níveis séricos de fósforo, cálcio, albumina, proteínas totais e atividade da fosfatase alcalina. RESULTADOS: O tamanho do calo ósseo foi maior no grupo submetido a tratamento combinando imobilização, exercício físico e testosterona. Os grupos tratados com testosterona combinada ou não a programa de natação apresentaram maiores níveis de fósforo e de fosfatase alcalina, além de menores níveis de proteínas totais e albumina. CONCLUSÃO: O grupo submetido ao programa de treinamento físico de natação combinado com a administração de testosterona obteve melhor consolidação óssea evidenciada pelo maior calo ósseo e atividade aumentada da fosfatase alcalina, sugerindo maior rapidez no processo de consolidação óssea.
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Kouzaki M, Masani K. Postural sway during quiet standing is related to physiological tremor and muscle volume in young and elderly adults. Gait Posture 2012; 35:11-7. [PMID: 21855345 DOI: 10.1016/j.gaitpost.2011.03.028] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/11/2010] [Revised: 02/18/2011] [Accepted: 03/22/2011] [Indexed: 02/02/2023]
Abstract
To examine the age-related deterioration in postural control, we investigated the association between postural sway during quiet standing and either amplitude of physiological tremor or muscle volume of the plantar flexors in 20 young and 20 elderly adults. They maintained a quiet standing position on a force platform for 60s with their eyes open or closed. During quiet standing, physiological tremors detected using a piezoresistive accelerometer were recorded from the soleus muscle, and the center of pressure (COP) displacement and body acceleration in the antero-posterior direction were calculated using the ground reaction forces as an assessment of postural sway. Muscle volume was predicted from muscle thickness by an ultrasonographic image. The physiological tremor of the soleus muscle during quiet standing was significantly greater in elderly than in young adults, and a positive association between physiological tremor and the amplitude of postural sway was found for young and elderly adults combined. Furthermore, physiological tremor was positively correlated with the high-frequency component of COP sway during quiet standing. A significantly negative relation between the muscle volume of the plantar flexors and postural sway was found in both age groups. These results suggest that physiological tremor reflects high-frequency fluctuations in postural sway during quiet standing in young and elderly adults, and age-related increases in the postural sway amplitude in the antero-posterior direction may be related to a decrease in muscle volume of the plantar flexors for maintaining an upright posture.
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Affiliation(s)
- Motoki Kouzaki
- Laboratory of Neurophysiology, Graduate School of Human and Environmental Studies, Kyoto University, Yoshida-nihonmatsu, Sakyo-ku, Kyoto, Japan.
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20
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Clark BC. In vivo alterations in skeletal muscle form and function after disuse atrophy. Med Sci Sports Exerc 2011; 41:1869-75. [PMID: 19727027 DOI: 10.1249/mss.0b013e3181a645a6] [Citation(s) in RCA: 82] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Prolonged reductions in muscle activity and mechanical loading (e.g., bed rest, cast immobilization) result in alterations in skeletal muscle form and function. The purpose of this review article was to synthesize recent findings from several studies on the dramatic effects of disuse on skeletal muscle morphology and muscle performance in humans. Specifically, the following are discussed: 1) how the antigravity muscles are most susceptible to atrophy and how the degree of atrophy varies between muscle groups; 2) how disuse alters muscle composition by increasing intermuscular adipose tissue; 3) the influence of different disuse models on regulating the loss of muscle mass and strength, with immobilization causing greater reductions than bed rest and limb suspension do; 4) the observation that disuse decreases strength to a greater extent than muscle mass and the role of adaptations in both neural and contractile properties that influences this excessive loss of strength; 5) the equivocal findings on the effect of disuse on muscle fatigue resistance; and 6) the reduction in motor control after prolonged disuse. Lastly, emerging data warranting further inquiry into the modulating role of biological sex on disuse-induced adaptations are also discussed.
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Affiliation(s)
- Brian C Clark
- Institute for Neuromusculoskeletal Research, Department of Biomedical Sciences, Ohio University College of Osteopathic Medicine, Athens, OH 45701, USA.
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21
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Chow JW, Stokic DS. Force control of quadriceps muscle is bilaterally impaired in subacute stroke. J Appl Physiol (1985) 2011; 111:1290-5. [DOI: 10.1152/japplphysiol.00462.2011] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
We tested the hypothesis that force variability and error during maintenance of submaximal isometric knee extension are greater in subacute stroke patients than in controls and are related to motor impairments. Contralesional (more-affected) and ipsilesional (less-affected) legs of 33 stroke patients with sufficiently high motor abilities (62 ± 13 yr, 16 ± 2 days postinjury) and the dominant leg of 20 controls (62 ± 10 yr) were tested in sitting position. After peak knee extension torque [maximum voluntary contraction (MVC)] was established, subjects maintained 10, 20, 30, and 50% of MVC as steady and accurate as possible for 10 s by matching voluntary force to the target level displayed on a monitor. Coefficient of variation (CV) and root-mean-square error (RMSE) were used to quantify force variability and error, respectively. The MVC was significantly smaller in the more-affected than less-affected leg, and both were significantly lower than in controls. The CV was significantly larger in the more-affected than less-affected leg at 20 and 50% MVC, whereas both were significantly larger compared with controls across all force levels. Both more-affected and less-affected legs of patients showed significantly greater RMSE than controls at 30 and 50% MVC. The CV and RMSE were not related to the Fugl-Meyer motor score or to the Rivermead Mobility Index. The CV negatively correlated with MVC in controls but only in the less-affected leg of patients. It is concluded that isometric knee extension strength and force control are bilaterally impaired soon after stroke but more so in the more-affected leg. Future studies should examine possible mechanisms and the evolution of these changes.
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Affiliation(s)
- John W. Chow
- Center for Neuroscience and Neurological Recovery, Methodist Rehabilitation Center, Jackson, Mississippi
| | - Dobrivoje S. Stokic
- Center for Neuroscience and Neurological Recovery, Methodist Rehabilitation Center, Jackson, Mississippi
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22
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Oshita K, Yano S. Asymmetry of force fluctuation during low and moderate intensity isometric knee extensions. Percept Mot Skills 2011; 112:860-70. [PMID: 21853775 DOI: 10.2466/15.25.26.pms.112.3.860-870] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
The purpose of this study was to investigate the asymmetry of force fluctuation during isometric knee extension at low and moderate intensities. 11 healthy men (M age = 21 yr., SD = 1) performed unilateral force matching tasks; sustained isometric knee extension at 20% and 30% maximal voluntary contraction (MVC). During the tasks, a mechanomyogram was measured by an accelerometer arrangement placed on the vastus lateralis. Although force fluctuation was not significantly different between the two legs at 20% MVC, it was higher in the left (weaker) leg than in the right (stronger) leg at 30% MVC. A significant difference in mean power frequency of the mechanomyographic signal between the two legs was also observed only at 30% MVC. These results suggest that the asymmetry of force fluctuation during isometric knee extension was not statistically significant at low intensity; however, it was significant at moderate intensity. These differences in force fluctuation between intensities might be influenced by different motor-unit firing rates in active muscle.
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Affiliation(s)
- Kazushige Oshita
- Department of Sports Science, Faculty of Sports Science, Kyushu Kyoritsu University, 1-8 Jiyugaoka, Yahatanishi-ku, Kitakyushu-city, Fukuoka 807-8585, Japan.
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23
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The loss of dexterity in the bilateral lower extremities in patients with stroke. J Appl Biomech 2011; 27:122-9. [PMID: 21576720 DOI: 10.1123/jab.27.2.122] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The aim of this study was to examine the dexterity of both lower extremities in patients with stroke. Twenty patients with stroke and 20 age-matched control subjects participated in this study. To determine the dexterity of the lower extremities, we examined the ability to control muscle force during submaximal contractions in the knee extensor muscles using a force tracking task. The root mean square errors were calculated from the difference between the target and response force. The root mean square error was significantly greater in the affected limb of patients with stroke compared with those of the unaffected limb and the control subjects, and in the unaffected limb compared with that of the control subjects. Furthermore, the root mean square error of the affected limb was related significantly to motor function as determined by Fugl-Myer assessment. These results demonstrate impairment of the dexterity of both the affected and the unaffected lower extremities in patients with stroke.
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24
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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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25
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Unilateral lower limb suspension: integrative physiological knowledge from the past 20 years (1991-2011). Eur J Appl Physiol 2011; 112:9-22. [PMID: 21533809 DOI: 10.1007/s00421-011-1971-7] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/08/2010] [Accepted: 04/15/2011] [Indexed: 10/18/2022]
Abstract
In 1991, Hans Berg and colleagues published the first research investigation using unilateral lower limb suspension (ULLS) as a human model to study the influence of unloading on skeletal muscle. ULLS requires a participant to perform all activities with axillary crutches while wearing one thick-soled shoe. The elevated shoe eliminates ground contact with the adjacent foot, thereby unloading the lower limb. Today, ULLS is a well-known ground-based analog for microgravity. The present review will synthesize the physiological findings from investigations using ULLS to study the deleterious effects of unloading. Compromised human performance and the neuromuscular, musculoskeletal and circulatory mechanisms leading to altered function will be a major emphasis of the work. Results from prolonged bed rest will also be included in order for general comparisons to be made between analogs. Finally, the efficacy of exercise to mitigate the negative consequences of unloading is presented.
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26
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Spiering BA, Lee SMC, Mulavara AP, Bentley JR, Buxton RE, Lawrence EL, Sinka J, Guilliams ME, Ploutz-Snyder LL, Bloomberg JJ. Test Battery Designed to Quickly and Safely Assess Diverse Indices of Neuromuscular Function After Unweighting. J Strength Cond Res 2011; 25:545-55. [DOI: 10.1519/jsc.0b013e3181f56780] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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27
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Mulder ER, Horstman AM, Gerrits K, Massa M, Kleine BU, de Haan A, Belavý DL, Felsenberg D, Zwarts M, Stegeman DF. Enhanced physiological tremor deteriorates plantar flexor torque steadiness after bed rest. J Electromyogr Kinesiol 2010; 21:384-93. [PMID: 21131213 DOI: 10.1016/j.jelekin.2010.10.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2010] [Revised: 10/18/2010] [Accepted: 10/18/2010] [Indexed: 11/17/2022] Open
Abstract
This study evaluated the effectiveness of resistance training to preserve submaximal plantar flexor (PF) torque steadiness following 60 days of bed rest (BR). Twenty-two healthy male subjects underwent either BR only (CTR, n=8), or BR plus resistance training (RT, n=14). The magnitude of torque fluctuations during steady submaximal isometric PF contractions (20%, 40%, 60% and 80% of maximum) were assessed before and after BR. Across contraction intensities, torque fluctuations (coefficient of variation, CV) increased more (P<0.05) after BR for CTR (from 0.31±0.10 to 0.92±0.63; P<0.001), than for RT (from 0.30±0.09 to 0.54±0.27; P<0.01). A shift in the spectral content of torque fluctuations towards increased rhythmic activity between 6.5 and 20Hz was observed in CTR only (P<0.05). H-reflex amplitude (H(max)/M(max) ratio) declined across groups from 0.57±0.18 before BR to 0.44±0.14 following BR (P<0.01) without correlation to CV. The present study showed that increased torque fluctuation after BR resulted from enhanced physiological tremor. Resistance training prevented the spectral shift in isometric PF torque fluctuation and offset ∼50% of the decline in performance associated with long-term BR.
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Affiliation(s)
- Edwin R Mulder
- Institute of Aerospace Medicine, Division of Space Physiology, German Space Center, Cologne, Germany.
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28
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Oshita K, Yano S. Relationship between force fluctuation in the plantar flexor and sustainable time for single-leg standing. J Physiol Anthropol 2010; 29:89-93. [PMID: 20558966 DOI: 10.2114/jpa2.29.89] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/02/2022] Open
Abstract
The purpose of this study was to investigate the relationships between force fluctuation during isometric plantar flexion and the sustainable time for single-leg standing. Fourteen healthy males (21+/-1 years) performed unilateral (preferred leg) force matching tasks and single-leg quiet standing. Force matching tasks were performed to maintain isometric plantar flexion for 15 s at levels corresponding to 10% and 20% maximal voluntary contraction (MVC) with the visual feedback of force. Force fluctuation during force matching tasks was quantified as the standard deviation of force. Sustainable time for single-leg quiet standing was performed to maintain a single-leg quiet standing barefoot on a platform using the preferred leg with their eyes closed. Force fluctuation was significantly greater in 20% MVC task compared to 10% MVC task. The sustainable time for single-leg quiet standing was strongly correlated with force fluctuation in 20% MVC task (r=-0.56, p=0.04). However, it was not related to force fluctuation in 10% MVC task (r=0.19, p=0.52) or MVC value (r=0.13, p=0.65). These results suggest that a specificity of contraction intensity is observed between force steadiness and the posture stability during single-leg quiet standing; force steadiness during 20% MVC plantar flexion is one of the important components for posture stability during single-leg quiet standing.
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Affiliation(s)
- Kazushige Oshita
- Graduate School of Human Development and Environment, Division of Human Environmental Science, Kobe University, Nada-ku, Kobe, Japan.
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29
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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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30
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Bandholm T, Rose MH, Sløk R, Sonne-Holm S, Jensen BR. Ankle torque steadiness is related to muscle activation variability and coactivation in children with cerebral palsy. Muscle Nerve 2009; 40:402-10. [PMID: 19662645 DOI: 10.1002/mus.21348] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
The aims of this study were to: (1) investigate the significance of muscle activation variability and coactivation for the ability to perform steady submaximal ankle torque (torque steadiness) in healthy children and those with cerebral palsy (CP), and (2) assess ankle function during isometric contractions in those children. Fourteen children with CP who walked with equinus foot deformity and 14 healthy (control) children performed maximal and steady submaximal ankle dorsi- and plantarflexions. Dorsiflexion torque steadiness was related to agonist and antagonist muscle activation variability as well as the plantarflexor coactivation level in children with CP (r > 0.624, P < 0.03). Moreover, children with CP displayed reduced maximal torque and submaximal torque steadiness of both dorsi- and plantarflexion compared with controls (P < 0.05). Both muscle groups may benefit from strength training, as they exhibit poor submaximal control and weakness in children with CP.
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Affiliation(s)
- Thomas Bandholm
- Gait Analysis Laboratory, (section 247), Department of Orthopedic Surgery, Hvidovre University Hospital, Kettegaard Allé 30, DK-2650, Copenhagen, Denmark.
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Chopard A, Hillock S, Jasmin BJ. Molecular events and signalling pathways involved in skeletal muscle disuse-induced atrophy and the impact of countermeasures. J Cell Mol Med 2009; 13:3032-50. [PMID: 19656243 PMCID: PMC4516463 DOI: 10.1111/j.1582-4934.2009.00864.x] [Citation(s) in RCA: 65] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Disuse-induced skeletal muscle atrophy occurs following chronic periods of inactivity such as those involving prolonged bed rest, trauma and microgravity environments. Deconditioning of skeletal muscle is mainly characterized by a loss of muscle mass, decreased fibre cross-sectional area, reduced force, increased fatigability, increased insulin resistance and transitions in fibre types. A description of the role of specific transcriptional mechanisms contributing to muscle atrophy by altering gene expression during muscle disuse has recently emerged and focused primarily on short period of inactivity. A better understanding of the transduction pathways involved in activation of proteolytic and apoptotic pathways continues to represent a major objective, together with the study of potential cross-talks in these cellular events. In parallel, evaluation of the impact of countermeasures at the cellular and molecular levels in short- and long-term disuse experimentations or microgravity environments should undoubtedly and synergistically increase our basic knowledge in attempts to identify new physical, pharmacological and nutritional targets to counteract muscle atrophy. These investigations are important as skeletal muscle atrophy remains an important neuromuscular challenge with impact in clinical and social settings affecting a variety of conditions such as those seen in aging, cancer cachexia, muscle pathologies and long-term space exploration.
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Affiliation(s)
- Angèle Chopard
- Department of Cellular and Molecular Medicine, Centre for Neuromuscular Disease, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada
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Camargo PR, Avila MA, de Oliveira AB, Asso NA, Benze BG, de Fátima Salvini T. Shoulder abduction torque steadiness is preserved in subacromial impingement syndrome. Eur J Appl Physiol 2009; 106:381-7. [PMID: 19294409 DOI: 10.1007/s00421-009-1030-9] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 02/25/2009] [Indexed: 10/21/2022]
Abstract
This study compared peak torque and torque steadiness during isometric abduction in subjects with subacromial impingement syndrome (SIS) and those with no upper limb disorders. The SIS group consisted of 27 subjects (33.48 +/- 9.94 years) with unilateral SIS. The control group consisted of 23 healthy and active subjects (32.26 +/- 9.04 years). Peak torque and torque steadiness were measured during isometric abduction (80 masculine in the scapular plane) of the shoulder. Standard deviation, coefficient of variation, stability time, median frequency, and relative power were measured from the steadiness trials. There were neither significant interactions between group and side (P > 0.05), nor were there significant main effects of group and side (P > 0.05) for all variables analyzed. The results of this study showed that steadiness is preserved by SIS during isometric abduction of the shoulder.
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Affiliation(s)
- Paula Rezende Camargo
- Department of Physical Therapy, Federal University of São Carlos, Rodovia Washington Luís, km 235, São Carlos, SP, 13565-905, Brazil
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SHINOHARA MINORU, YOSHITAKE YASUHIDE, KOUZAKI MOTOKI. Alterations in Synergistic Muscle Activation Impact Fluctuations in Net Force. Med Sci Sports Exerc 2009; 41:191-7. [DOI: 10.1249/mss.0b013e318183c0d9] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Clark BC, Issac LC, Lane JL, Damron LA, Hoffman RL. Neuromuscular plasticity during and following 3 wk of human forearm cast immobilization. J Appl Physiol (1985) 2008; 105:868-78. [PMID: 18635877 DOI: 10.1152/japplphysiol.90530.2008] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Prolonged reductions in muscle activity results in alterations in neuromuscular properties; however, the time course of adaptations is not fully understood, and many of the specific adaptations have not been identified. This study evaluated the temporal evolution of adaptations in neuromuscular properties during and following 3 wk of immobilization. We utilized a combination of techniques involving nerve stimulation and transcranial magnetic stimulation to assess changes in central activation of muscle, along with spinal (H reflex) and corticospinal excitability [i.e., motor-evoked potential (MEP) amplitude, silent period (SP)] and contractile properties in 10 healthy humans undergoing 3 wk of forearm immobilization and 9 control subjects. Immobilization induced deficits in central activation (85 +/- 3 to 67 +/- 7% ) that returned to baseline levels 1 wk after cast removal. The flexor carpii radialis MEP amplitude increased greater than twofold after the first week of immobilization and remained elevated throughout immobilization and 1 wk after cast removal. Additionally, we observed a prolongation of the SP 1 wk after cast removal compared with baseline (78.5 +/- 7.1 to 98.2 +/- 8.7 ms). The contractile properties were also altered, since the rate of evoked force relaxation was slower following immobilization (-14.5 +/- 1.4 to -11.3 +/- 1.0% peak force/ms), and remained depressed 1 wk after cast removal (-10.5 +/- 0.8% peak force/ms). These observations detail the time course of adaptations in corticospinal and contractile properties associated with disuse and illustrate the profound effect of immobilization on the human neuromuscular system as evidenced by the alterations in corticospinal excitability persisting 1 wk following cast removal.
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Affiliation(s)
- Brian C Clark
- Dept. of Biomedical Sciences, Ohio Univ. College of Osteopathic Medicine, Athens, OH 45701, USA.
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Bandholm T, Rose MH, Sonne-Holm S, Jensen BR. Assessment of torque-steadiness reliability at the ankle level in healthy young subjects: implications for cerebral palsy. Eur J Appl Physiol 2008; 104:609-15. [DOI: 10.1007/s00421-008-0808-5] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2008] [Indexed: 11/24/2022]
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Motor variability: within-subject correlations during separate and simultaneous contractions. Exp Brain Res 2008; 189:159-70. [PMID: 18478208 DOI: 10.1007/s00221-008-1412-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2007] [Accepted: 04/29/2008] [Indexed: 10/22/2022]
Abstract
To determine the similarity of motor variability in proximal muscles, young and elderly adults performed steady elbow flexor (EF) and knee extensor (KE) contractions separately (SEP; at 2.5, 30, and 65% of maximum) and simultaneously (SIM; at 2.5 and 30% of maximum), with (VIS) and without (NVIS) visual feedback. Between-muscle correlations of fluctuation amplitude (SD, CV of force), time-based cross-correlations (CC), force power spectra, and frequency-based coherence (COH) values were computed from the concurrent force records. Correlations of fluctuation amplitude ranged from r = 0.34 to 0.86 (P < 0.05) across forces, SEP/SIM, and vision conditions, but were absent for 2.5% NVIS. The relatively low CC values for SIM (r = 0.22-0.33) were stronger for elderly than young adults. The vast majority of the power in the force fluctuations was <4 Hz for all records. Weak COH peaks were only observed <2 Hz for elderly and between 3 and 4 Hz for young, and COH was slightly stronger for elderly below 3 Hz for the 30% MVC target force. The correlations in force fluctuation amplitude suggest that the EF and KE motor neuron pools similarly transform the oscillating synaptic input and may influence each other. The cross-correlations suggest the remote motor neuron pools are influenced similarly in time by a common source of excitation, perhaps more coherently for elderly adults at low frequencies.
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Lundbye-Jensen J, Nielsen JB. Central nervous adaptations following 1 wk of wrist and hand immobilization. J Appl Physiol (1985) 2008; 105:139-51. [PMID: 18450985 DOI: 10.1152/japplphysiol.00687.2007] [Citation(s) in RCA: 79] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Plastic neural changes have been documented in relation to different types of physical activity, but little is known about central nervous system plasticity accompanying reduced physical activity and immobilization. In the present study we investigated whether plastic neural changes occur in relation to 1 wk of immobilization of the nondominant wrist and hand and a corresponding period of recovery in 10 able-bodied volunteers. After immobilization, maximal voluntary contraction torque decreased and the variability of submaximal static contractions increased significantly without evidence of changes in muscle contractile properties. Hoffmann (H)-reflex amplitudes and the ratios of H-slope to M-slope increased significantly in flexor carpi radialis and abductor pollicis brevis at rest and during contraction without changes in corticospinal excitability, estimated from motor-evoked potentials (MEPs) elicited by transcranial magnetic stimulation. Corticomuscular coherence measures were derived from EEG and EMG obtained during static contractions. After immobilization, corticomuscular coherence in the 15- to 35-Hz range associated with maximum negative cumulant values at lags corresponding to MEP latencies decreased. One week after cast removal, all measurements returned to preimmobilization levels. The increased H-reflex amplitudes without changes in MEPs may suggest that presynaptic inhibition or postactivation depression of Ia afferents is reduced following immobilization. Reduced corticomuscular coherence may be caused by changes in afferent input at spinal and cortical levels or by changes in the descending drive from motor cortex. Further studies are needed to elucidate the mechanisms underlying the observed increased spinal excitability and reduced coupling between motor cortex and spinal motoneuronal activity following immobilization.
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Affiliation(s)
- Jesper Lundbye-Jensen
- Department of Neuroscience and Pharmacology, University of Copenhagen, Panum Institute 22.3, Blegdamsvej 3, Copenhagen 2200, Denmark.
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Shinohara M, Keenan KG, Enoka RM. Fluctuations in motor output of a hand muscle can be altered by the mechanical properties of the position sensor. J Neurosci Methods 2008; 168:164-73. [PMID: 17964659 DOI: 10.1016/j.jneumeth.2007.09.015] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2007] [Revised: 09/14/2007] [Accepted: 09/17/2007] [Indexed: 11/17/2022]
Abstract
Fluctuations in motor output are typically quantified by the standard deviation (SD) of displacement or acceleration. The aim of the study was to determine the influence of a linear variable-displacement transducer (LVDT) on the SDs and spectral content of displacement and acceleration during steady isometric and anisometric contractions performed with the first dorsal interosseus muscle. Thirteen young adults supported six loads when performing position-holding and position-tracking tasks when the LVDT either was or was not attached to the index finger. The LVDT reduced the magnitude of the SDs in displacement and acceleration and disrupted the load-dependent modulation of the spectral properties of these signals. When the LVDT was not connected to the finger, the displacement SD was greatest during concentric contractions, the acceleration SD was greatest during eccentric contractions, and there were load-dependent changes in the power density spectra. Although the LVDT may be used for assessing relative changes in displacement, its ability to provide absolute measures of fluctuations in motor output is limited. The results provide baseline measures of the fluctuations in motor output during steady contractions with a hand muscle and how the method used to detect displacement alters these measures.
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Affiliation(s)
- Minoru Shinohara
- Department of Integrative Physiology, University of Colorado at Boulder, USA.
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Pavy-Le Traon A, Heer M, Narici MV, Rittweger J, Vernikos J. From space to Earth: advances in human physiology from 20 years of bed rest studies (1986-2006). Eur J Appl Physiol 2007; 101:143-94. [PMID: 17661073 DOI: 10.1007/s00421-007-0474-z] [Citation(s) in RCA: 375] [Impact Index Per Article: 22.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/13/2007] [Indexed: 01/11/2023]
Abstract
Bed rest studies of the past 20 years are reviewed. Head-down bed rest (HDBR) has proved its usefulness as a reliable simulation model for the most physiological effects of spaceflight. As well as continuing to search for better understanding of the physiological changes induced, these studies focused mostly on identifying effective countermeasures with encouraging but limited success. HDBR is characterised by immobilization, inactivity, confinement and elimination of Gz gravitational stimuli, such as posture change and direction, which affect body sensors and responses. These induce upward fluid shift, unloading the body's upright weight, absence of work against gravity, reduced energy requirements and reduction in overall sensory stimulation. The upward fluid shift by acting on central volume receptors induces a 10-15% reduction in plasma volume which leads to a now well-documented set of cardiovascular changes including changes in cardiac performance and baroreflex sensitivity that are identical to those in space. Calcium excretion is increased from the beginning of bed rest leading to a sustained negative calcium balance. Calcium absorption is reduced. Body weight, muscle mass, muscle strength is reduced, as is the resistance of muscle to insulin. Bone density, stiffness of bones of the lower limbs and spinal cord and bone architecture are altered. Circadian rhythms may shift and are dampened. Ways to improve the process of evaluating countermeasures--exercise (aerobic, resistive, vibration), nutritional and pharmacological--are proposed. Artificial gravity requires systematic evaluation. This review points to clinical applications of BR research revealing the crucial role of gravity to health.
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Affiliation(s)
- A Pavy-Le Traon
- Service D'explorations Fonctionnelles Respiratoires Et d'analyses Physiologiques, Hopital La Cavale Blanche, University Hospital of Brest, 29609, Brest Cedex, France.
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Kouzaki M, Masani K, Akima H, Shirasawa H, Fukuoka H, Kanehisa H, Fukunaga T. Effects of 20-day bed rest with and without strength training on postural sway during quiet standing. Acta Physiol (Oxf) 2007; 189:279-92. [PMID: 17305708 DOI: 10.1111/j.1748-1716.2006.01642.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
AIM To examine the effect of unweighting as a possible contributory factor to a reduced calf muscle volume on postural sway during quiet standing, changes in postural sway following bed rest with or without strength training were investigated. METHODS Twelve young men participated in a 20-day bed-rest study. Subjects were divided into a non-training group (BR-Con) and a strength training group (BR-Tr). For the BR-Tr group, training was comprised of dynamic calf-raise and leg-press exercises to maintain the muscle volume of the plantar flexors. Before and after bed rest, subjects maintained quiet standing in a barefoot position on a force platform with their eyes open or closed. During the quiet stance, foot centre-of-pressure (CoP) and the mean velocity of CoP was calculated. Muscle volume of the plantar flexors was computed using axial magnetic resonance images of the leg. RESULTS After the bed-rest period, the muscle volume decreased in the BR-Con group but not in the BR-Tr group. The mean velocity of CoP as an assessment of postural sway, however, increased in both groups. These results indicate that the strength training during bed rest cannot counteract the increase in postural sway. CONCLUSION We concluded that postural sway increases following 20 days of bed rest despite maintenance of the muscle volume of plantar flexors as the main working muscles for the human postural standing.
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Affiliation(s)
- M Kouzaki
- Department of Life Sciences, Graduate School of Arts and Sciences, The University of Tokyo, Tokyo, Japan.
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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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43
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Bandholm T, Rasmussen L, Aagaard P, Jensen BR, Diederichsen L. Force steadiness, muscle activity, and maximal muscle strength in subjects with subacromial impingement syndrome. Muscle Nerve 2006; 34:631-9. [PMID: 16921511 DOI: 10.1002/mus.20636] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
We investigated the effects of the subacromial impingement syndrome (SIS) on shoulder sensory-motor control and maximal shoulder muscle strength. It was hypothesized that both would be impaired due to chronic shoulder pain associated with the syndrome. Nine subjects with unilateral SIS who remained physically active in spite of shoulder pain and nine healthy matched controls were examined to determine isometric and isokinetic submaximal shoulder-abduction force steadiness at target forces corresponding to 20%, 27.5%, and 35% of the maximal shoulder abductor torque, and maximal shoulder muscle strength (MVC). Electromyographic (EMG) activity was assessed using surface and intramuscular recordings from eight shoulder muscles. Force steadiness was impaired in SIS subjects during concentric contractions at the highest target force level only, with muscle activity largely unaffected. No between-group differences in shoulder MVC were observed. The present data suggest that shoulder sensory-motor control is only mildly impaired in subjects with SIS who are able to continue with upper body physical activity in spite of shoulder pain. Thus, physical activity should be continued by patients with SIS, if possible, to avoid the loss in neural and muscle functions associated with inactivity.
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Affiliation(s)
- Thomas Bandholm
- Institute of Exercise and Sport Sciences, Department of Human Physiology, University of Copenhagen, Copenhagen, Denmark.
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44
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Abstract
Measurement of the transverse displacement of the skin over a contracting muscle is known as the surface mechanomyogram. With the concurrent measurement of the electromyogram and twitch force, the mechanomyogram can provide supplementary information about muscle activity and motor performance during such tasks as fatiguing contractions and attempts to perform steady contractions.
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Affiliation(s)
- Minoru Shinohara
- Department of Integrative Physiology, University of Colorado, Boulder, Colorado 80309-0354, USA.
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45
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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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Manini TM, Clark BC, Tracy BL, Burke J, Ploutz-Snyder L. Resistance and functional training reduces knee extensor position fluctuations in functionally limited older adults. Eur J Appl Physiol 2005; 95:436-46. [PMID: 16193338 DOI: 10.1007/s00421-005-0048-x] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/04/2005] [Indexed: 11/25/2022]
Abstract
The purpose of this study was to determine the effect of task-specificity on knee extensor steadiness adaptations in functionally limited older adults. Twenty-four functionally limited older adults (74.6+/-7.6 years: 22 women, 2 men) completed a 10-week control period followed by 10 weeks (2 days/week) of resistance (RT), functional (FT) (practicing everyday tasks, i.e., chair rises) or functional + resistance (FRT) training, which featured both shortening and lengthening movements. During testing, subjects performed a steady isometric [10, 25, 50% of maximal voluntary contraction (MVC)] and shortening/lengthening (5, 30, 65% of MVC) knee extensor contractions. There were no steadiness (isometric, shortening or lengthening contractions) changes in the control period and no adaptations in isometric steadiness due to training. RT induced a 37% reduction in shortening fluctuations at 5% of MVC and 35% reduction in lengthening fluctuations at both 30% and 65% of MVC. FRT induced a 60% reduction in shortening fluctuations at 30% of MVC. No adaptations in dynamic steadiness were observed in the FT group. Further analysis indicated that those who were the least steady at baseline showed the greatest training effects during isometric (RT: R (2)=0.25, FRT: R (2)=0.49, FT: R (2)=0.38), shortening (RT: R (2)=0.36, FRT: R (2)=0.36, FT: R (2)=0.35) and lengthening (RT: r (2)=0.29, FRT: r (2)=0.44) contractions. In conclusion, steadiness improvements in groups performing resistance exercise, without a concomitant improvement in the FT group, supports a role for task-specificity in explaining steadiness adaptations, particularly for unsteady older adults.
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Affiliation(s)
- Todd M Manini
- Musculoskeletal Research Laboratory, Syracuse University, Syracuse, NY, USA.
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47
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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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48
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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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Clark BC, Collier SR, Manini TM, Ploutz-Snyder LL. Sex differences in muscle fatigability and activation patterns of the human quadriceps femoris. Eur J Appl Physiol 2005; 94:196-206. [PMID: 15791418 DOI: 10.1007/s00421-004-1293-0] [Citation(s) in RCA: 132] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2004] [Accepted: 11/10/2004] [Indexed: 11/28/2022]
Abstract
The purposes of this study were to determine if the fatigability of the quadriceps femoris varies by biological sex under conditions of normal muscle blood flow and ischemia, and if differences in neuromuscular activation patterns exist. Young men and women (n = 11/group; age 20-39 years) performed a sustained knee extension contraction at 25% of maximal force under conditions of occluded (OCC) and normal muscle blood flow (NON-OCC). Electromyographic (EMG) activity was recorded from the vastus lateralis (VL), rectus femoris (RF), vastus medialis (VM) and biceps femoris (BF) muscles, and analyzed for fatigue-induced changes in the amplitude and burst rate and duration (transient changes in motor unit recruitment) of the signal. Additionally, force fluctuations during the sustained contraction were quantified. Women had a longer time to task failure during the NON-OCC task [214.9 +/- 20.5 vs. 169.1 +/- 20.5 (SE) s] (P = 0.02), but not during the OCC task (179.6 + 19.6 vs. 165.2 +/- 19.6 s). EMG data demonstrated sex differences in the neuromuscular activation pattern of the RF muscle and the collectively averaged QF muscles. During the NON-OCC and OCC tasks women achieved a higher relative activation of the RF at task failure than men (NON-OCC: 40.68 +/- 4.57 vs. 24.49 +/- 4.19%; OCC: 36.80 +/- 5.45 vs. 24.41 +/- 2.12%) (P = 0.02 and 0.05, respectively). Also, during both tasks, they demonstrated a greater relative activation at task failure than men when an average of the VL, VM and RF was considered. Additionally, women exhibited a greater coefficient of variation in force fluctuations during the last-third of the fatiguing NON-OCC task (6.21 +/- 0.567 vs. 4.56 +/- 0.56%) (P = 0.001). No sex differences in EMG burst rate or duration were observed, although there was a trend towards greater EMG burst rate of the RF in association with muscle fatigue in the women (P = 0.09). Interestingly, the only neuromuscular activation variable that displayed a significant relationship with the time to task failure was the average relative EMG of the QF at task failure, and this relationship was observed under both experimental blood flow conditions (NON-OCC: r = 0.47, P = 0.03; OCC: r = 0.44, P = 0.04). These results indicate that sex differences in muscle blood flow and/or muscle metabolism are in part responsible for the female advantage in fatigue-resistance. Additionally, these findings suggest that men synergistically recruit the RF compartment to a lesser extent than women in association with muscle fatigue, and that women achieve an overall greater relative activation of the QF at task failure than men. However, the implications of these sex differences in neuromuscular activation patterns during fatiguing muscular contractions on the ability to withstand muscle fatigue (prolonged time to task failure) does not appear to be causally related.
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Affiliation(s)
- Brian C Clark
- Musculoskeletal Research Laboratory, Department of Exercise Science, Syracuse University, NY 13244, USA.
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Shinohara M, Keenan KG, Enoka RM. Fluctuations in motor output during steady contractions are weakly related across contraction types and between hands. Muscle Nerve 2005; 31:741-50. [PMID: 15795890 DOI: 10.1002/mus.20326] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
Abstract
The presence of differences in motor unit activity across contraction types and between hands suggests that the magnitude of fluctuations in motor output is only weakly related when these conditions are compared. Twenty right-handed young (24.1 +/- 5.3 years) and old (72.5 +/- 4.9 years) adults performed three levels (</=40% of maximal force) of isometric and anisometric contractions with the first dorsal interosseous muscle of each hand. The fluctuations in motor output were quantified by the coefficient of variation for force during isometric contractions, and as the standard deviations of acceleration and position during anisometric contractions. There was no effect of age on fluctuations in motor output. The magnitude of the fluctuations in motor output was weakly related across contraction types (r(2) < 0.325) and between hands (r(2) < 0.262). Furthermore, the standard deviations of acceleration and position during shortening and lengthening contractions were largely unrelated to one another. Because the activity in a motor unit population differed across contraction types and hands during steady contractions, the central nervous system likely employed distinct strategies to accomplish these different tasks.
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Affiliation(s)
- Minoru Shinohara
- Department of Integrative Physiology, University of Colorado, 354 UCB, Boulder, Colorado 80309-0354, USA.
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