Search results for "Fatigue"
showing 10 items of 651 documents
Proposition d'une conceptualisation et d'une classification des problèmes de fatigue mécanique
2010
National audience; On propose de conceptualiser les problèmes de calcul de structure dits de fatigue et d'en déduire une classification allant de la plus complexe à la plus simple. Parce que le concept de fatigue est avant tout un concept que l'on peut estimer structural plutôt que local, une première classification est basée sur des paramètres représentatifs des sollicitations structurales. Ensuite, une seconde classification est basée sur des paramètres représentatifs de l'état local de la variable d'état "pilote" (déformation, contrainte...). L'objectif visé est d'aider à la résolution des problèmes structuraux complexes de fatigue en tenant compte du caractère tridimensionnel et non uni…
Adaptations neuromusculaires des muscles extenseurs du genou : contractions fatigantes uni- vs bi-latérales
2010
The aim of this work was to determine i) the influence of the level of absolute force on the duration of the endurance time, and subsequent neuromuscular alterations in same individual at the end of an exercise performed at the same relative intensity, with one or two legs, ii) the influence of central drive on the force capacity production of the knee extensor muscles during unilateral (UL) vs. bilateral (BL) contractions, iii) activation mechanisms evolution for a serie of submaximal evoked contractions by electrostimulation (EMS). The results of the first study confirm that the endurance limit depends on the level of absolute force for the same individual, contraction duration for UL is …
Contribution to the design of a smart electromyostimulator
2013
This project aims to develop a new tool for neuromuscular reeducation. Its function is to improve the quality and the duration of muscular strengthening training sessions and training of motor function for patients suffering from muscle deconditioning. A "smart" electromyostimulator using, at the same time, techniques of electrostimulation (EMS) and analysis of electromyography (EMG) allows the control in real time electrical stimulation parameters considering the physiological fatigue of the stimulated muscle. This control, performed on stimulation parameters depending on electrical response of muscles (M wave), allows the muscle stimulation taking into account the muscular reaction to the…
La correspondance d'Elizabeth Gaskell et son œuvre : engagement et discrétion
2010
Les liens entre la correspondance de Gaskell et son œuvre sont assez lâches. Les lettres indiquent clairement les motivations de l'auteur et éclairent les principes qui guident ses choix narratifs (ainsi que la difficulté de les respecter). Elles parlent aussi clairement de la fatigue de l'écrivain et de ses causes. Mais elles sont beaucoup moins explicites en ce qui concerne l'écriture même. Si nous arrivons à nous faire une idée du processus de composition, les choses deviennent plus difficiles quand il s'agit des choix esthétiques et stylistiques. Nous n'avons en fait que des traces ou des remarques d'ordre général. Quant à l'utilisation des lettres comme d'un laboratoire d'écriture elle…
Altération des performances neuromusculaires après un exercice physique prolongé. Analyse comparée d'une épreuve de marathon et de triathlon
1998
The aim of this study was to compare the effects of a marathon and a triathlon on isometric and dynamic neuromuscular performances. Seven triathletes took part in 3 experimental situations : a 2 h 15 mn triathlon (TRI) (30 min swimming, 60 min cycling and 45 min running), a 2 h 15 mn marathon (MA) and a 45 min isolated run done at triathlon speed. The results showed a reduction of the isometric endurance time for knee extensor muscles (35 % of maximal voluntary contraction) after TRI (41 ± 24 %) and after MA (59 ± 19 %). The height of rise of the center of gravity of the counter-movement jumps (CMJ) was also significantly lower after MA (-12 ± 1 cm) than after TRI (-2,5 0,5 cm). Kinetic ana…
Study of fatigue behavior of plant fiber reinforced composites : taking into account the variability of properties
2012
The present study focuses on the characterization and comparison of the quasi-static and fatigue properties of flax and glass fibre reinforced composites with an epoxy matrix. An extensive experimental campaign of fatigue tests have been performed using the measured quasi-static tension and in plane-shear properties. It appears that the static and fatigue characteristics of the glass/epoxy composites are higher than that of flax/epoxy ones with similar fibre volume fraction and lay-ups. However, due to the low density of flax reinforcements, the differences between the specific properties of the two materials are low. The measurement of the evolution of the fatigue properties has highlighte…
Comportement en fatigue thermomécanique à haute température d’un système barrière thermique texturé par laser
2020
In service life of Thermal Barrier Coating (TBC) systems for blade applications can be limited by the top-coat (TC) spallation under thermo-mechanical fatigue (TMF) loadings. To improve its TMF life, laser texturing at the bond-coat/top coat interface in the CMSX-4 Plus / γ-γ’ BC/ EB-PVD TC system has been investigated.Thanks to the study of the laser-matter interaction, it seems that the different Ni-based single crystal superalloys have similar laser ablation behaviors and they present almost no sub-surface damage after ablation. Nevertheless, the formation of melted matter near created cavities, possibly recrystallized, is often observed.Different patterns (holes, lines, grids) have been…
FATIGUE, SLEEP, AND NOCTURNAL COMPLAINTS IN PATIENTS WITH AMYOTROPHIC LATERAL SCLEROSIS.
2012
Background and purpose: Fatigue is a common symptom in amyotrophic lateral sclerosis (ALS). Although sleep disturbances are a candidate factor that may interfere with fatigue in patients with ALS, the role of sleep-related abnormalities in determining fatigue in ALS is unknown. Objective: To evaluate the frequency and determinants of fatigue in a group of 91 consecutive patients with ALS, with special attention to the relationship between fatigue and sleep problems. Methods: Measures included the Fatigue Severity Scale (FSS), Pittsburgh Sleep Quality Index (PSQI), Epworth Sleepiness Scale (ESS), ALS Functional Rating Scale- Revised (ALSFRS-R), and Beck Depression Inventory (BDI). Results: T…
Short-time non-work-related computing and creative performance
2014
It has been argued that non-work-related computing (NWRC) takes time away from work and, hence, decreases work productivity. On the other hand, it has also been claimed that short-time non-work-related computing (STNWRC) (a maximum of 15 minutes), has a positive impact on work productivity, including relief from boredom, higher creativity, and the underlying recovery mechanisms. To examine the impact of STNWRC on creative performance, we draw on Fredrickson's broaden-and-build theory, the concept of recovery with mental well-being and low cognitive effort. A 2 × 2 factorial experiment with 40 subjects was conducted. The results indicate that STNWRC has a positive effect on creative performa…
A global experiment on motivating social distancing during the COVID-19 pandemic
2022
Significance\ud \ud Communicating in ways that motivate engagement in social distancing remains a critical global public health priority during the COVID-19 pandemic. This study tested motivational qualities of messages about social distancing (those that promoted choice and agency vs. those that were forceful and shaming) in 25,718 people in 89 countries. The autonomy-supportive message decreased feelings of defying social distancing recommendations relative to the controlling message, and the controlling message increased controlled motivation, a less effective form of motivation, relative to no message. Message type did not impact intentions to socially distance, but people’s existing mo…