Virginie Kluka1,2, Vincent Martin1, Sebastian Garcia Vicencio1, Mathias Giustiniani3, Claire Morel3, Cédric Morio2, Emmanuel Coudeyre3,4,5, Sébastien Ratel6. 1. Clermont Auvergne University, Blaise Pascal University, EA 3533, Laboratory of Metabolic Adaptations During Exercise in Physiological and Pathological Conditions (AME2P), BP 80026, F-63171, Aubière Cedex, France. 2. Decathlon Research, Department of Movement Sciences, Villeneuve d'Asq, France. 3. Clermont University Hospital, Clermont-Ferrand, France. 4. INRA, Unité de Nutrition Humaine (UNH, UMR 1019), CRNH Auvergne, Clermont-Ferrand, France. 5. Université Clermont Auvergne, Université d'Auvergne, Clermont-Ferrand, France. 6. Clermont Auvergne University, Blaise Pascal University, EA 3533, Laboratory of Metabolic Adaptations During Exercise in Physiological and Pathological Conditions (AME2P), BP 80026, F-63171, Aubière Cedex, France. sebastien.ratel@univ-bpclermont.fr.
Abstract
PURPOSE: The aim of the present study was to compare the effect of muscle length on the maximal voluntary activation level (VA) of the plantar-flexors between children and adults. METHODS: Fourteen boys (10.0 ± 1.0 years) and fifteen men (24.6 ± 4.2 years) performed 5-s maximal isometric voluntary contractions (MVC) of the plantar-flexor muscles at seven ankle angles [from 10° in dorsi-flexion (DF) to 20° in plantar-flexion (PF); 0° = reference position; the angle between the plantar surface and leg is a right angle]. Single magnetic stimulations were delivered to the posterior tibial nerve during MVCs to determine VA. RESULTS: Results showed a higher absolute torque of the plantar-flexor muscles at long (10° DF) than at short muscle length (20° PF) in men (89.4 ± 19.4 vs. 46.8 ± 17.0 N m, P < 0.001) and boys (44.9 ± 18.5 vs. 26.6 ± 12.8 N m, P < 0.001). On average, VA was significantly higher in men than in boys (92.4 ± 1.7 vs. 87.6 ± 1.6 %, P < 0.05). However, no significant main effect of the ankle angle was observed on VA. CONCLUSIONS: The VA partly accounts for the plantar-flexors MVC torque difference between children and adults but is not affected by the muscle length changes in both groups. Therefore, VA cannot account for the shape of the torque-angle relationship on the plantar-flexor muscles.
PURPOSE: The aim of the present study was to compare the effect of muscle length on the maximal voluntary activation level (VA) of the plantar-flexors between children and adults. METHODS: Fourteen boys (10.0 ± 1.0 years) and fifteen men (24.6 ± 4.2 years) performed 5-s maximal isometric voluntary contractions (MVC) of the plantar-flexor muscles at seven ankle angles [from 10° in dorsi-flexion (DF) to 20° in plantar-flexion (PF); 0° = reference position; the angle between the plantar surface and leg is a right angle]. Single magnetic stimulations were delivered to the posterior tibial nerve during MVCs to determine VA. RESULTS: Results showed a higher absolute torque of the plantar-flexor muscles at long (10° DF) than at short muscle length (20° PF) in men (89.4 ± 19.4 vs. 46.8 ± 17.0 N m, P < 0.001) and boys (44.9 ± 18.5 vs. 26.6 ± 12.8 N m, P < 0.001). On average, VA was significantly higher in men than in boys (92.4 ± 1.7 vs. 87.6 ± 1.6 %, P < 0.05). However, no significant main effect of the ankle angle was observed on VA. CONCLUSIONS: The VA partly accounts for the plantar-flexors MVC torque difference between children and adults but is not affected by the muscle length changes in both groups. Therefore, VA cannot account for the shape of the torque-angle relationship on the plantar-flexor muscles.
Entities:
Keywords:
Childhood; Magnetic stimulation; Motor unit recruitment; Torque
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