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      Bilateral Strength Deficit Is Not Neural in Origin; Rather Due to Dynamometer Mechanical Configuration

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          Abstract

          During maximal contractions, the sum of forces exerted by homonymous muscles unilaterally is typically higher than the sum of forces exerted by the same muscles bilaterally. However, the underlying mechanism(s) of this phenomenon, which is known as the bilateral strength deficit, remain equivocal. One potential factor that has received minimal attention is the contribution of body adjustments to bilateral and unilateral force production. The purpose of this study was to evaluate the plantar-flexors in an innovative dynamometer that permitted the influence of torque from body adjustments to be adapted. Participants were identically positioned between two setup configurations where torques generated from body adjustments were included within the net ankle torque (locked-unit) or independent of the ankle (open-unit). Twenty healthy adult males performed unilateral and bilateral maximal voluntary isometric plantar-flexion contractions using the dynamometer in the open and locked-unit mechanical configurations. While there was a significant bilateral strength deficit in the locked-unit (p = 0.01), it was not evident in the open-unit (p = 0.07). In the locked-unit, unilateral torque was greater than in the open-unit (p<0.001) and this was due to an additional torque from the body since the electromyographic activity of the agonist muscles did not differ between the two setups (p>0.05). This study revealed that the mechanical configuration of the dynamometer and then the body adjustments caused the observation of a bilateral strength deficit.

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          Most cited references 41

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          Development of recommendations for SEMG sensors and sensor placement procedures.

           H Hermens,  C Klug,  G. C. Rau (2000)
          The knowledge of surface electromyography (SEMG) and the number of applications have increased considerably during the past ten years. However, most methodological developments have taken place locally, resulting in different methodologies among the different groups of users.A specific objective of the European concerted action SENIAM (surface EMG for a non-invasive assessment of muscles) was, besides creating more collaboration among the various European groups, to develop recommendations on sensors, sensor placement, signal processing and modeling. This paper will present the process and the results of the development of the recommendations for the SEMG sensors and sensor placement procedures. Execution of the SENIAM sensor tasks, in the period 1996-1999, has been handled in a number of partly parallel and partly sequential activities. A literature scan was carried out on the use of sensors and sensor placement procedures in European laboratories. In total, 144 peer-reviewed papers were scanned on the applied SEMG sensor properties and sensor placement procedures. This showed a large variability of methodology as well as a rather insufficient description. A special workshop provided an overview on the scientific and clinical knowledge of the effects of sensor properties and sensor placement procedures on the SEMG characteristics. Based on the inventory, the results of the topical workshop and generally accepted state-of-the-art knowledge, a first proposal for sensors and sensor placement procedures was defined. Besides containing a general procedure and recommendations for sensor placement, this was worked out in detail for 27 different muscles. This proposal was evaluated in several European laboratories with respect to technical and practical aspects and also sent to all members of the SENIAM club (>100 members) together with a questionnaire to obtain their comments. Based on this evaluation the final recommendations of SENIAM were made and published (SENIAM 8: European recommendations for surface electromyography, 1999), both as a booklet and as a CD-ROM. In this way a common body of knowledge has been created on SEMG sensors and sensor placement properties as well as practical guidelines for the proper use of SEMG.
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            Movement, posture and equilibrium: interaction and coordination.

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              Reliability and validity of the Biodex system 3 pro isokinetic dynamometer velocity, torque and position measurements.

              This study quantitatively assessed the mechanical reliability and validity of position, torque and velocity measurements of the Biodex System 3 isokinetic dynamometer. Trial-to-trial and day-to-day reliability were assessed during three trials on two separate days. To assess instrument validity, measurement of each variable using the Biodex System 3 dynamometer was compared to a criterion measure of position, torque and velocity. Position was assessed at 5 degrees increments across the available range of motion of the dynamometer. Torque measures were assessed isometrically by hanging six different calibrated weights from the lever arm. Velocity was assessed (30 degrees/s to 500 degrees/s) across a 70 degrees arc of motion by manually accelerating the weighted lever arm. With the exception of a systematic decrease in velocity at speeds of 300 degrees/s and higher, the Biodex System 3 performed with acceptable mechanical reliability and validity on all variables tested.
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                Author and article information

                Contributors
                Role: Editor
                Journal
                PLoS One
                PLoS ONE
                plos
                plosone
                PLoS ONE
                Public Library of Science (San Francisco, CA USA )
                1932-6203
                18 December 2015
                2015
                : 10
                : 12
                Affiliations
                [1 ]Laboratoire d'Automatique, de Mécanique et d'Informatique industrielles et Humaines (LAMIH)–UMR CNRS 8201, Université de Valenciennes et du Hainaut-Cambrésis (UVHC), Valenciennes, France
                [2 ]Laboratoire de l’Effort et du Mouvement, Haute Ecole Provinciale de Hainaut (HEPH)—Condorcet, Tournai, Belgium
                [3 ]School of Health and Exercise Sciences, University of British Columbia Okanagan, Kelowna, Canada
                Semmelweis University, HUNGARY
                Author notes

                Competing Interests: The authors have declared that no competing interests exist.

                Conceived and designed the experiments: ESB SL FG JJ. Performed the experiments: ESB SL AT AD. Analyzed the data: ESB SL FB JJ. Contributed reagents/materials/analysis tools: ESB SL AT FG FB JJ. Wrote the paper: ESB SL AT AD FG FB JJ.

                Article
                PONE-D-15-14488
                10.1371/journal.pone.0145077
                4684274
                26684828
                © 2015 Simoneau-Buessinger et al

                This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited

                Page count
                Figures: 3, Tables: 0, Pages: 11
                Product
                Funding
                The authors received no specific funding for this work.
                Categories
                Research Article
                Custom metadata
                Due to ethical restrictions, data are available upon request to all interested researchers via the corresponding author ( emilie.simoneau@ 123456univ-valenciennes.fr ).

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