Time filter

Source Type

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.


Hu X.-Q.,CNRS Biomechanical Engineering Laboratory | Salsac A.-V.,CNRS Biomechanical Engineering Laboratory | Barthes-Biesel D.,CNRS Biomechanical Engineering Laboratory
Journal of Fluid Mechanics | Year: 2012

The motion and deformation of a spherical elastic capsule freely flowing in a pore of comparable dimension is studied. The thin capsule membrane has a neo-Hookean shear softening constitutive law. The three-dimensional fluid-structure interactions are modelled by coupling a boundary integral method (for the internal and external fluid motion) with a finite element method (for the membrane deformation). In a cylindrical tube with a circular cross-section, the confinement effect of the channel walls leads to compression of the capsule in the hoop direction. The membrane then tends to buckle and to fold as observed experimentally. The capsule deformation is three-dimensional but can be fairly well approximated by an axisymmetric model that ignores the folds. In a microfluidic pore with a square cross-section, the capsule deformation is fully three-dimensional. For the same size ratio and flow rate, a capsule is more deformed in a circular than in a square cross-section pore. We provide new graphs of the deformation parameters and capsule velocity as a function of flow strength and size ratio in a square section pore. We show how these graphs can be used to analyse experimental data on the deformation of artificial capsules in such channels. © 2011 Cambridge University Press.


Prot J.M.,CNRS Biomechanical Engineering Laboratory | Leclerc E.,CNRS Biomechanical Engineering Laboratory
Annals of Biomedical Engineering | Year: 2012

In this paper, we will consider new in vitro cell culture platforms and the progress made, based on the microfluidic liver biochips dedicated to pharmacological and toxicological studies. Particular emphasis will be given to recent developments in the microfluidic tools dedicated to cell culture (more particularly liver cell culture), in silico opportunities for Physiologically Based PharmacoKinetic (PBPK) modelling, the challenge of the mechanistic interpretations offered by the approaches resulting from "multi-omics" data (transcriptomics, proteomics, metabolomics, cytomics) and imaging microfluidic platforms. Finally, we will discuss the critical features regarding microfabrication, design and materials, and cell functionality as the key points for the future development of new microfluidic liver biochips. © 2011 Biomedical Engineering Society.


Lapole T.,Laboratoire APERE Adaptations Physiologiques a lExercice et Readaptation a | Perot C.,CNRS Biomechanical Engineering Laboratory
Applied Physiology, Nutrition and Metabolism | Year: 2012

In a previous study, Achilles tendon vibrations were enough to improve the triceps surae (TS) activation capacities and also to slightly increase TS Hoffmann reflex (H-reflex) obtained by summing up soleus (Sol) and gastrocnemii (GM and GL) EMGs. The purpose of the present study was to analyze separately Sol and GM or GL reflexes to account for different effects of the vibrations on the reflex excitability of the slow soleus and of the gastrocnemii muscles. A control group (n = 13) and a vibration group (n = 16) were tested in pre-test and post-test conditions. The Achilles tendon vibration program consisted of 1 h of daily vibration (frequency: 50 Hz) applied during 14 days. Maximal Sol, GM and GL H-reflexes, and M-waves were recorded, and their H max/M max ratios gave the index of reflex excitability. After the vibration protocol, only Sol H max/M max was enhanced (p < 0.001). The enhanced Sol reflex excitability after vibration is in favor of a decrease in the pre-synaptic inhibition due to the repeated vibrations and the high solicitation of the reflex pathway. Those results of a short period of vibration applied at rest may be limited to the soleus because of its high density in muscle spindles and slow motor units, both structures being very sensitive to vibrations.


Zhang L.,CNRS Biomechanical Engineering Laboratory | Salsac A.-V.,CNRS Biomechanical Engineering Laboratory
Journal of Colloid and Interface Science | Year: 2012

The objective is to investigate the influence of sonication on the mechanical and release properties of hydrogel capsules. A new fabrication process is developed to fabricate millimetric capsules made of a highly-viscous liquid core protected by a thin hyperelastic alginate membrane. At high intensities and/or long exposure times, sonication can lead to the capsule rupture, because it induces fatigue in the membrane. Below the breakup threshold, no remnant effect of sonication is, however, measured on the capsule mechanical properties. The release is studied by sonicating capsules filled with blue dextran suspended in an aqueous solution. The mass release that results from sonication is found to be proportional to the sonication duration time and pressure wave amplitude. A possible physical interpretation is that the acoustic streaming flow induced by the ultrasonic wave enhances convection in the vicinity of the capsule membrane and thus mass release. We have finally quantified the passive release subsequent to low-intensity sonications: it is on average identical to the one measured on non-sonicated capsules. Overall the membrane therefore recovers its physical and mechanical properties after sonication. If sonication leads to an increase in porosity of the capsule membrane, the increase is temporary and reverses back at the end of the ultrasonic stimulation. © 2011 Elsevier Inc.


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.


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.


Fadel O.,Compiègne University of Technology | El Kirat K.,CNRS Biomechanical Engineering Laboratory | Morandat S.,Compiègne University of Technology
Biochimica et Biophysica Acta - Biomembranes | Year: 2011

Exogenous molecules from dietary sources such as polyphenols are very efficient in preventing the alteration of lipid membranes by oxidative stress. Among the polyphenols, we have chosen to study rosmarinic acid (RA). We investigated the efficiency of RA in preventing lipid peroxidation and in interacting with lipids. We used liposomes of 1,2-dilinoleoyl-sn-glycero-3- phosphocholine (DLPC) to show that RA was an efficient antioxidant. By HPLC, we determined that the maximum amount of RA associated with the lipids was ~ 1 mol%. Moreover, by using Langmuir monolayers, we evidenced that cholesterol decreases the penetration of RA. The investigation of transferred lipid/RA monolayers by atomic force microscopy revealed that 1 mol% of RA in the membrane was not sufficient to alter the membrane structure at the nanoscale. By fluorescence, we observed no significant modification of membrane permeability and fluidity caused by the interaction with RA. We also deduced that RA molecules were mainly located among the polar headgroups of the lipids. Finally, we prepared DLPC/RA vesicles to evidence for the first time that up to 1 mol% of RA inserts spontaneously in the membrane, which is high enough to fully prevent lipid peroxidation without any noticeable alteration of the membrane structure due to RA insertion. © 2011 Elsevier B.V.


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.


El Kirat K.,CNRS Biomechanical Engineering Laboratory | Morandat S.,Compiègne 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.

Loading CNRS Biomechanical Engineering Laboratory collaborators
Loading CNRS Biomechanical Engineering Laboratory collaborators