Vastus lateralis surface and single motor unit EMG following submaximal shortening and lengthening contractions
| Autor: | C.J. de Ruiter, P. W. L. Verdijk, Teatske M. Altenburg, A. de Haan, W. van Mechelen |
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| Přispěvatelé: | Movement Behavior, Kinesiology, Faculty of Human Movement Sciences, EMGO+ - Musculoskeletal Health, Research Institute MOVE, Public and occupational health, EMGO - Musculoskeletal health, MOVE Research Institute |
| Rok vydání: | 2008 |
| Předmět: |
Adult
Male medicine.medical_specialty Time Factors Physiology Endocrinology Diabetes and Metabolism Electromyography Quadriceps Muscle Voluntary contraction Reference Values Physiology (medical) Internal medicine Isometric Contraction Muscle Stretching Exercises medicine Humans Knee Motor Neurons Nutrition and Dietetics Knee extensors medicine.diagnostic_test Chemistry Muscle activation General Medicine Anatomy Motor unit Electrophysiology Motor unit recruitment Cardiology Female medicine.symptom Muscle contraction Muscle Contraction |
| Zdroj: | Applied Physiology, Nutrition, and Metabolism = Physiologie Appliquée, Nutrition et Métabolisme, 33(6), 1086-1095. National Research Council of Canada Altenburg, T M, de Ruiter, C J, Verdijk, P W L, van Mechelen, W & de Haan, A 2008, ' Vastus lateralis surface and single motor unit EMG following submaximal shortening and lengthening contractions ', Applied Physiology, Nutrition, and Metabolism = Physiologie Appliquée, Nutrition et Métabolisme, vol. 33, no. 6, pp. 1086-1095 . https://doi.org/10.1139/H08-092 Altenburg, T M, de Ruiter, C J, Verdijk, P W L, van Mechelen, W & de Haan, A 2008, ' Vastus lateralis surface and single motor unit EMG following submaximal shortening and lengthening contractions ', Physiologie Appliquée Nutrition et Métabolisme, vol. 33, no. 6, pp. 1086-1095 . https://doi.org/10.1139/H08-092 Physiologie Appliquée Nutrition et Métabolisme, 33(6), 1086-1095. National Research Council of Canada |
| ISSN: | 1715-5312 |
| DOI: | 10.1139/h08-092 |
| Popis: | A single shortening contraction reduces the force capacity of muscle fibers, whereas force capacity is enhanced following lengthening. However, how motor unit recruitment and discharge rate (muscle activation) are adapted to such changes in force capacity during submaximal contractions remains unknown. Additionally, there is limited evidence for force enhancement in larger muscles. We therefore investigated lengthening- and shortening-induced changes in activation of the knee extensors. We hypothesized that when the same submaximal torque had to be generated following shortening, muscle activation had to be increased, whereas a lower activation would suffice to produce the same torque following lengthening. Muscle activation following shortening and lengthening (20° at 10°/s) was determined using rectified surface electromyography (rsEMG) in a 1st session (at 10% and 50% maximal voluntary contraction (MVC)) and additionally with EMG of 42 vastus lateralis motor units recorded in a 2nd session (at 4%–47%MVC). rsEMG and motor unit discharge rates following shortening and lengthening were normalized to isometric reference contractions. As expected, normalized rsEMG (1.15 ± 0.19) and discharge rate (1.11 ± 0.09) were higher following shortening (p < 0.05). Following lengthening, normalized rsEMG (0.91 ± 0.10) was, as expected, lower than 1.0 (p < 0.05), but normalized discharge rate (0.99 ± 0.08) was not (p > 0.05). Thus, muscle activation was increased to compensate for a reduced force capacity following shortening by increasing the discharge rate of the active motor units (rate coding). In contrast, following lengthening, rsEMG decreased while the discharge rates of active motor units remained similar, suggesting that derecruitment of units might have occurred. |
| Databáze: | OpenAIRE |
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