Repetitive eccentric muscle contractions increase torque unsteadiness in the human triceps brachii |
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| Authors: | Andrew J Meszaros Masaki Iguchi Shuo-Hsiu Chang Richard K Shields |
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| Institution: | 1. Neuroscience Department, College of Medicine, University of Toledo, Toledo, OH, USA;2. Physical Therapy and Rehabilitation Science, Carver College of Medicine, The University of Iowa, Iowa City, IA, USA;1. Universidade da Coruña, NEUROcom (Neuroscience and Motor Control Group) and Biomedical Institute of A Coruña (INIBIC), Department of Medicine-INEF Galicia, A Coruña, Spain;2. EMG Unit, Neurology Service, Hospital Clinic, Department of Medicine, University of Barcelona, August Pi i Sunyer Biomedical Research Institute (IDIBAPS), Barcelona, Spain;3. FENNSI Group, Hospital Nacional de Parapléjicos, SESCAM, Toledo, Spain;4. Centro de Estimulación Cerebral de Galicia, A Coruña, Spain;1. Centre for Human and Applied Physiology, School of Health Sciences, University of Wollongong, Australia;2. Fire and Rescue NSW, Australia;1. Division of Pediatric Infectious Diseases, Department of Pediatrics, Medical School, UTHealth, Houston, TX, USA;2. Division of Child and Adolescent Neurology, Department of Pediatrics, Medical School, UTHealth, Houston, TX, USA;3. Division of Community and General Pediatrics, Department of Pediatrics, Medical School, UTHealth, Houston, TX, USA;1. Athletic Training and Sports Medicine Research Laboratory, Department of Kinesiology, The Pennsylvania State University, University Park, Pennsylvania, U.S.A.;2. Penn State Hershey Bone and Joint Institute, State College, State College, Pennsylvania, U.S.A.;1. Faculty of Health Sciences, Mejiro University, 320 Ukiya Iwatuki-ku Saitama-shi Saitama, 339-8501, Japan;2. Tokyo Metropolitan Geriatric Hospital and Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo, 173-0015, Japan;3. Department of Allied Health Science. Kitasato University, Sagamihara-shi Kanagawa, Japan |
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| Abstract: | Torque steadiness and low-frequency fatigue (LFF) were examined in the human triceps brachii after concentric or eccentric fatigue protocols. Healthy young males (n = 17) performed either concentric or eccentric elbow extensor contractions until the eccentric maximal voluntary torque decreased to 75% of pre-fatigue for both (concentric and eccentric) protocols. The number of concentric contractions was greater than the number of eccentric contractions needed to induce the same 25% decrease in eccentric MVC torque (52.2 ± 2.9 vs. 41.5 ± 2.1 for the concentric and eccentric protocols, respectively, p < .01). The extent of peripheral fatigue was ～12% greater after the concentric compared to the eccentric protocol (twitch amplitude), whereas LFF (increase in double pulse torque/single pulse torque), was similar across protocols. Steadiness, or the ability for a subject to hold a submaximal isometric contraction, was ～20 % more impaired during the Ecc protocol (p = .052). Similarly, the EMG activity required to hold the torque steady was nearly 20% greater after the eccentric compared to concentric protocol. These findings support that task dependent eccentric contractions preferentially alter CNS control during a precision based steadiness task. |
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