Baptiste Morel1,2, François Hug3,4, Antoine Nordez3,5, Hervé Pournot1, Thibault Besson1, Laure Mathevon1, Thomas Lapole1. 1. University of Saint-Etienne, Inter-university Laboratory of Human Movement Science, University of Lyon, Saint-Etienne, FRANCE. 2. Laboratory "Movement, Interactions, Performance," Faculty of Sciences and Technologies, Department of Sport Sciences, Le Mans University, Le Mans, FRANCE. 3. Laboratory "Movement, Interactions, Performance," Faculty of Sport Sciences, University of Nantes, Nantes, FRANCE. 4. Institut Universitaire de France, Paris, FRANCE. 5. Health and Rehabilitation Research Institute, Faculty of Health and Environmental Sciences, Auckland University of Technology, Auckland, NEW ZEALAND.
Abstract
PURPOSE: Whether muscle stiffness is influenced by fatigue remains unclear. Classical methods used to assess muscle stiffness provide a global measure at the joint level. As fatigue may selectively affect specific muscles, a joint-level approach may not be sensitive enough to detect potential changes in muscle stiffness. Taking advantage of ultrasound shear wave elastography, this study aimed to determine the influence of a fatiguing protocol involving intermittent submaximal isometric contractions on muscle shear modulus (an index of stiffness). METHODS: Shear modulus was measured on either the vastus lateralis (n = 9) or the abductor digiti minimi (n = 10) before and after 15 min of intermittent submaximal isometric contractions at 60% of maximal voluntary contraction (MVC) (4 s ON, 4 s OFF). An index of active muscle stiffness was estimated PRE- and POST-fatigue as the slope of the linear regression established between shear modulus and absolute joint force up to 60% MVC. RESULTS: After the fatiguing exercise, MVC was significantly decreased by 22% ± 7% and 32% ± 15% for knee extension and little finger abduction, respectively (P < 0.001). When compared to PRE-fatigue, the index of active muscle stiffness was 12% ± 15% lower for the vastus lateralis (P < 0.031) and 44% ± 19% lower for the abductor digiti minimi (P < 0.001) POST-fatigue. CONCLUSIONS: Although the present results cannot clearly determine the involved mechanisms, they demonstrate a decreased active muscle stiffness after a fatiguing task involving intermittent submaximal isometric contractions. Further studies should now determine whether this change in stiffness affects performance and risk of injury.
PURPOSE: Whether muscle stiffness is influenced by fatigue remains unclear. Classical methods used to assess muscle stiffness provide a global measure at the joint level. As fatigue may selectively affect specific muscles, a joint-level approach may not be sensitive enough to detect potential changes in muscle stiffness. Taking advantage of ultrasound shear wave elastography, this study aimed to determine the influence of a fatiguing protocol involving intermittent submaximal isometric contractions on muscle shear modulus (an index of stiffness). METHODS: Shear modulus was measured on either the vastus lateralis (n = 9) or the abductor digiti minimi (n = 10) before and after 15 min of intermittent submaximal isometric contractions at 60% of maximal voluntary contraction (MVC) (4 s ON, 4 s OFF). An index of active muscle stiffness was estimated PRE- and POST-fatigue as the slope of the linear regression established between shear modulus and absolute joint force up to 60% MVC. RESULTS: After the fatiguing exercise, MVC was significantly decreased by 22% ± 7% and 32% ± 15% for knee extension and little finger abduction, respectively (P < 0.001). When compared to PRE-fatigue, the index of active muscle stiffness was 12% ± 15% lower for the vastus lateralis (P < 0.031) and 44% ± 19% lower for the abductor digiti minimi (P < 0.001) POST-fatigue. CONCLUSIONS: Although the present results cannot clearly determine the involved mechanisms, they demonstrate a decreased active muscle stiffness after a fatiguing task involving intermittent submaximal isometric contractions. Further studies should now determine whether this change in stiffness affects performance and risk of injury.
Authors: Bruno Mendes; Telmo Firmino; Raúl Oliveira; Tiago Neto; Carlos Cruz-Montecinos; Mauricio Cerda; José P Correia; João R Vaz; Sandro R Freitas Journal: Sci Rep Date: 2020-10-02 Impact factor: 4.379
Authors: Sandro Bartolomei; Federico Nigro; Ivan Malagoli Lanzoni; Anna Lisa Mangia; Matteo Cortesi; Simone Ciacci; Silvia Fantozzi Journal: Int J Environ Res Public Health Date: 2021-05-03 Impact factor: 3.390