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Lapole T.,University of Picardie Jules Verne | Perot C.,CNRS Biomechanical Engineering Laboratory
Journal of Electromyography and Kinesiology | Year: 2010

Many studies reported benefits of whole-body vibration (WBV) on muscle force production. Therefore, WBV may be an important technique for muscle re-education. However vibrating platforms are heavy tools that cannot be easily used by all patients. Thus, we propose to apply vibrations directly to the Achilles tendon at rest with a portable vibrator. We investigated whether 14 days of such a vibration program would enhance triceps surae force production in healthy subjects. If successful, such a protocol could be utilized to prevent deleterious effects of hypo-activity. Twenty-nine healthy students participated in this study. The electrical evoked twitch and maximal voluntary contraction (MVC) in plantar-flexion, and electromyograms (EMG) were quantified before and at the end of the program. The vibration program consisted of 14 days of daily vibration applied at rest (duration: 1 h; frequency: 50 Hz). After the program, there was an increase in MVC associated with greater EMG of the TS. No sign of hypertrophy were found on the twitch parameters and the EMG-torque relationships. Repeated vibrations of the Achilles tendon lead to an increase in plantar-flexor activation and thus to greater force developed in voluntary conditions whilst the contractile properties assessed by the twitch are not modified. This program could be beneficial to persons with hypo-activity who are not candidates for WBV. © 2010 Elsevier Ltd. Source


Barthes-Biesel D.,CNRS Biomechanical Engineering Laboratory
Annual Review of Fluid Mechanics | Year: 2016

This article reviews the mechanical behavior of a capsule under the influence of viscous deforming forces due to a flowing fluid. It focuses on artificial capsules and vesicles with an internal liquid core enclosed by a very thin membrane with different constitutive laws. The recent modeling strategies are outlined together with their respective advantages and limitations. I then consider the motion and deformation of a single, initially spherical capsule freely suspended in a simple shear or plane hyperbolic flow and discuss the effect of the membrane constitutive law, initial prestress, membrane buckling, and bulk or membrane viscosity. Finally, I consider the flow of spherical capsules in small pores and show how numerical models can be used to evaluate the mechanical properties of the membrane. © Copyright 2016 by Annual Reviews. All rights reserved. Source


Lapole T.,University of Picardie Jules Verne | Perot C.,CNRS Biomechanical Engineering Laboratory
Journal of Electromyography and Kinesiology | Year: 2011

Clinical studies frequently report an increase in stiffness and a loss of range of motion at joints placed in disuse or immobilization. This is notably the case for subjects maintained in bed for a long period, whilst their joints are not affected. Recently we documented on healthy subjects the benefit in terms of force and activation capacities of the triceps surae offered by vibrations applied to the Achilles tendon. Knowing that stiffness changes may contribute to force changes, the aim of the present study was to investigate the effects of tendon vibration on the triceps surae stiffness of healthy subjects. The vibration program consisted in 14. days of 1. h daily Achilles tendon vibration applied at rest. Nineteen healthy students were involved in this study. Before and at the end of the vibration program, musculo-tendinous stiffness in active conditions was determined by use of a quick-release test. Passive stiffness was also analyzed by a flexibility test: passive torque-angle relationships were established from maximal plantar-flexion to maximal dorsiflexion. Passive stiffness indexes at 10°, 15° and 20° dorsiflexion were defined as the slope of the relationships at the corresponding angle. Tendinous reflex, influenced by stiffness values, was also investigated as well as the H reflex to obtain an index of the central reflex excitability. After the program, musculo-tendinous stiffness was significantly decreased (p=01). At the same time, maximal passive dorsiflexion was increased (p=005) and passive stiffness indexes at 10°, 15° and 20° dorsiflexion decreased (P<001; P<001 and p=011, respectively). Tendinous reflex also significantly decreased. As the triceps surae parameters are diminished after the vibration program, it could be beneficial to immobilized persons as hypo-activity is known to increase muscular stiffness. © 2010 Elsevier Ltd. Source


El Kirat K.,CNRS Biomechanical Engineering Laboratory | Morandat S.,Compiegne University of Technology | Dufrene Y.F.,Catholic University of Louvain
Biochimica et Biophysica Acta - Biomembranes | Year: 2010

During the past 15 years, atomic force microscopy (AFM) has opened new opportunities for imaging supported lipid bilayers (SLBs) on the nanoscale. AFM offers a means to visualize the nanoscale structure of SLBs in physiological conditions. A unique feature of AFM is its ability to monitor dynamic events, like bilayer alteration, remodelling or digestion, upon incubation with various external agents such as drugs, detergents, proteins, peptides, nanoparticles, and solvents. Here, we survey recent progress made in the area. © 2009 Elsevier B.V. All rights reserved. Source


Barthes-Biesel D.,CNRS Biomechanical Engineering Laboratory
Current Opinion in Colloid and Interface Science | Year: 2011

This review presents the mechanical behavior of a capsule under the influence of viscous deforming forces due to a flowing fluid. We focus on artificial capsules that are initially spherical with an internal liquid core and that are enclosed by a very thin hyperelastic membrane with different constitutive laws. The recent modeling strategies are outlined together with their respective advantages and limitations. We then consider the motion and deformation of a single initially spherical capsule freely suspended in a simple shear or plane hyperbolic flow and discuss the effect of the membrane constitutive law, of initial pre-stress and of membrane buckling under compression. We then consider the flow of spherical capsules in small pores and show how it can be used to evaluate the mechanical properties of the membrane. © 2010 Elsevier Ltd. Source

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