Motor unit firing patterns of lower leg muscles during isometric plantar flexion with flexed knee joint position |
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| Affiliation: | 1. Laboratory of Neuromuscular Biomechanics, School of Health and Sport Science, Chukyo University, 101 Tokodachi, Kaizu-cho, Toyota-shi, Aichi 470-0393, Japan;2. Faculty of Electrical Engineering and Computer Science, University of Maribor, Koroška cesta 46, 2000 Maribor, Slovenia;3. Toyota Motor Corporation, 1 Toyotacho, Toyota-shi, Aichi 471-8571, Japan;1. Research Centre on Aging, CIUSSS de l’Estrie - CHUS, Sherbrooke, QC, Canada;2. Department of Mechanical Engineering, Université de Sherbrooke, Sherbrooke, QC, Canada;3. School of Rehabilitation, Université de Sherbrooke, Sherbrooke, QC, Canada;4. Department of Health Sciences, Université du Québec à Chicoutimi, Chicoutimi, QC, Canada;5. Research Centre on Health, CIUSSS du Saguenay-Lac-Saint-Jean, Chicoutimi, QC, Canada;1. Faculty of Medicine, Memorial University of Newfoundland, St. John’s, NL, Canada;2. Division of Research and Innovation, Canadian Memorial Chiropractic College, Toronto, ON, Canada;1. Programa de Engenharia Biomédica (COPPE), Universidade Federal do Rio de Janeiro, Rio de Janeiro, RJ, Brazil;2. Centre of Precision Rehabilitation for Spinal Pain (CPR Spine), School of Sport, Exercise and Rehabilitation Sciences, College of Life and Environmental Sciences, University of Birmingham, Birmingham, UK;3. Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy;4. Laboratorio di Ingegneria del Sistema Neuromuscolare (LISiN), Politecnico di Torino, Torino, TO, Italy;5. PolitoBIOMed Lab, Politecnico di Torino, Torino, Italy;1. Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Bitlis Eren University, Bitlis, Turkey;2. Department of Physical Therapy and Rehabilitation, Institute of Health Sciences, Dokuz Eylul University, Izmir, Turkey;3. Department of Physiotherapy and Rehabilitation, Faculty of Health Sciences, Istanbul Medipol University, Istanbul, Turkey;1. Laboratório de Biomecânica Muscular, Escola de Educação Física e Desportos, Universidade Federal do Rio de Janeiro, Rio de Janeiro, Brazil;2. Department of Clinical and Experimental Sciences, Università degli Studi di Brescia, Brescia, Italy;1. Univ Lyon, UJM-Saint-Etienne, Laboratoire Interuniversitaire de Biologie de la Motricité, EA 7424, F-42023 Saint-Etienne, France;2. Université du Québec à Montréal (UQAM), Montréal, Canada;3. Unité de Myologie, Service de Physiologie Clinique et de l’Exercice, Centre Référent Maladies Neuromusculaires Euro-NmD, CHU de Saint-Etienne, France;4. Institut Universitaire de France (IUF), Paris, France |
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| Abstract: | The ankle flexor and extensor muscles are essential for pedal movements associated with car driving. Neuromuscular activation of lower leg muscles is influenced by the posture during a given task, such as the flexed knee joint angle during car driving. This study aimed to investigate the influence of flexion of the knee joint on recruitment threshold-dependent motor unit activity in lower leg muscles during isometric contraction. Twenty healthy participants performed plantar flexor and dorsiflexor isometric ramp contractions at 30 % of the maximal voluntary contraction (MVC) with extended (0°) and flexed (130°) knee joint angles. High-density surface electromyograms were recorded from medial gastrocnemius (MG), soleus (SOL), and tibialis anterior (TA) muscles and decomposed to extract individual motor units. The torque-dependent change (Δpps /Δ%MVC) of the motor unit activity of MG (recruited at 15 %MVC) and SOL (recruited at 5 %MVC) muscles was higher with a flexed compared with an extended knee joint (p < 0.05). The torque-dependent change of TA MU did not different between the knee joint angles. The motor units within certain limited recruitment thresholds recruited to exert plantar flexion torque can be excited to compensate for the loss of MG muscle torque output with a flexed knee joint. |
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| Keywords: | EMG Flexed knee joint Isometric contraction Motor unit Torque-dependent change |
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