VALIDITY, SENSITIVITY AND REPRODUCIBILITY OF STAGES AND GARMIN VECTOR POWER METERS WHEN COMPARED WITH SRM DEVICE

The measurement of power output (PO) during cycling has led some manufacturers to develop mobile power meters. However, such devices have to provide a valid, sensitive and reproducible PO. This study aimed to determine the validity, sensitivity and reproducibility of the Stages and Garmin Vector during both laboratory and field cycling tests. The results demonstrate that the Stages and the Garmin Vector systems appear to be reproducible. However, the validity and the sensitivity of the two systems must be treated with some caution

Etude de la puissance mécanique comme variable d'amélioration de la performance en cyclisme à travers l'interface homme-machine

This thesis has been completed as part of a CIFRE agreement between the laboratory C3S(EA4660) and the Research and Development (R&D) department of the FDJ professionalcycling team. The various studies that we conducted centred on analysing sport performanceoptimisation in cyclists through a central variable: the mechanical power output (PO)developed during locomotion. There were two main areas of focus: 1) evaluation andmonitoring of physical potential, with the aim of improving the training process, and 2)optimisation of the human–machine interface via analysis of the materials and equipmentused by the FDJ team cyclistsCe travail de thèse s’est déroulé dans le cadre d’une convention CIFRE entre mon laboratoire de rattachement C3S (EA4660) et le département Recherche et Développement (R&D) de l’équipe cycliste professionnelle FDJ. Les différentes études que nous avons conduites se sont articulées autour de l’amélioration de la performance sportive chez le cycliste à travers une variable centrale qui est la puissance mécanique qu’il développe lors de la locomotion (Pméca) selon deux axes principaux : 1) l’évaluation et le suivi du potentiel physique avec pour but l’amélioration du processus d’entraînement et 2) l’optimisation de l’interface homme – machine à partir de l’analyse du matériel et des équipements utilisés par les cyclistes dans l’équipe FDJ

Évaluation de la durée de séjour par la création d’une consultation intermédiaire de médecine générale au sortir d’une hospitalisation en unité polyvalente dans le bassin thiernois

Introduction : Les patients des zones de désertification médicale notamment rurales rencontrent des difficultés d’accès aux soins en sortie d’hospitalisation. Une consultation de médecine générale intra-hospitalière dite « passerelle » assurant un suivi intermédiaire des patients sur le centre hospitalier de Thiers est proposée.Objectif : Évaluation de la diminution de la durée de séjour par la création d’une consultation intermédiaire de suivi des patients hospitalisés dans le service de médecine polyvalente de Thiers.Méthodes : Inclusion des patients hospitalisés dans le service du 1er janvier 2018 au 1er septembre 2018 avec recueil de données. Initiation des consultations à partir du 1er mai 2018. Analyse comparative entre les 2 groupes : de janvier à avril n’ayant pas accès à la consultation et de mai à août avec accès à la consultation.Résultats : 627 patients ont été inclus, 334 de janvier à avril et 293 de mai à août sans différence significative sur la moyenne d’âge (p=0,15) et le sexe (p=0,46). Les diagnostics principaux ont été regroupés en 20 cadres nosologiques avec un p=0,48 sur la période. Le devenir des patients était comparable dans les 2 groupes.La durée médiane de séjour était de 9 jours [6-13] dans le groupe de janvier à avril contre 8 jours [5-13] dans le groupe de mai à août avec p=0,06. Le taux de ré-hospitalisation à 30 jours était de 13,5% contre 18,8% avec p=0,07.Conclusion : On observe une diminution de la durée médiane de séjour dans le groupe ayant eu accès à une consultation de suivi de médecine générale intra-hospitalière, même si celle-ci reste non significative. Parallèlement, on retrouve une augmentation du taux de réhospitalisation dans ce groupe qui est également non significative. Une étude comparative prolongée dans le temps permettrait de mieux caractériser ces tendances

Analysis of the mechanical power output as a parameter to improve cycling performance through the study of the human-machine interface

Ce travail de thèse s’est déroulé dans le cadre d’une convention CIFRE entre mon laboratoire de rattachement C3S (EA4660) et le département Recherche et Développement (R&D) de l’équipe cycliste professionnelle FDJ. Les différentes études que nous avons conduites se sont articulées autour de l’amélioration de la performance sportive chez le cycliste à travers une variable centrale qui est la puissance mécanique qu’il développe lors de la locomotion (Pméca) selon deux axes principaux : 1) l’évaluation et le suivi du potentiel physique avec pour but l’amélioration du processus d’entraînement et 2) l’optimisation de l’interface homme – machine à partir de l’analyse du matériel et des équipements utilisés par les cyclistes dans l’équipe FDJ.This thesis has been completed as part of a CIFRE agreement between the laboratory C3S(EA4660) and the Research and Development (R&D) department of the FDJ professionalcycling team. The various studies that we conducted centred on analysing sport performanceoptimisation in cyclists through a central variable: the mechanical power output (PO)developed during locomotion. There were two main areas of focus: 1) evaluation andmonitoring of physical potential, with the aim of improving the training process, and 2)optimisation of the human–machine interface via analysis of the materials and equipmentused by the FDJ team cyclist

Understanding the mechanisms influencing the growth of metallic foams made by plasmaelectrolysis deposition : application in laser targets fabrication.

Pour le besoin des expériences laser menées par le CEA, une nouvelle méthode dedépôt par plasma électrolytique a été conçue et brevetée afin de fabriquer des mousses métalliques ultra légères et nanostructurées. Ce procédé innovant et unique au monde consiste à créer et maintenir un plasma à la surface d’une électrode plongée dans un électrolyte aqueux. Dans le but de pouvoir maîtriser la synthèse des mousses métalliques, il est nécessaire d’identifier et de comprendre les multiples processus impliqués dans la formation des mousses (création d’une poche de gaz, génération du plasma, propagation des décharges électriques, interaction plasma-liquide, cristallisation des brins métalliques…).Sur les bases d’un modèle phénoménologique issu de précédents travaux, cette thèse se concentre sur l’étude de la croissance des mousses métalliques de l’échelle macroscopique à l’échelle microscopique. Les observations réalisées permettent de mettre en évidence que la structure des mousses et la morphologie des brins résultent de la propagation de “streamers” au sein de l’électrolyte. Puis en déterminant les conditions de réduction des ions métalliques lors de la synthèse de mousses d’alliage, ces travaux semblent montrer que la formation des brins de mousse ne résulte pas d’un mécanisme d’électrocristallisation en milieu liquide mais plutôt en milieu plasma. En conséquence, un nouveau modèle de croissance des mousses métalliques cohérent avec les nouvelles observations est proposé.For the CEA laser experimentations, a new plasma electrolysis deposition process tomanufacture nanostructured and low density metallic foams has been patented. This unique and innovative method consists in producing and stabilizing a plasma at the surface of an electrode immerged in an aqueous electrolyte. In order to control the metallic foam synthesis, it is important to identify and understand the multiples phenomena involved in the foams formation (gas sheath creation, plasmageneration, electrical discharges propagation, plasma-liquid interaction, metallic strands crystallization...).On the basis of a phenomenological model from a previous work, this PhD thesis focuses on the study of the metallic foams’ growth from the macroscopic to the microscopic scale. The observations reveal that the foams structure as well as the morphology of the strands result from the propagation of “streamers” inside the electrolyte. By determining the conditions for the reduction of metallic ions within the synthesis of alloys foams, this work seems to show that the strands formation does not results from an electrocristallisation mechanism inside the liquid but more probably inside the plasma. A new coherent model for the foam growth is then proposed

Validity, Sensitivity, Reproducibility and Robustness of the Powertap, Stages and Garmin Vector Power Meters in Comparison With the SRM Device

International audienceA large number of power meters were produced on the market for nearly 20 years and according to user requirements. Purpose: This study aimed to determine the validity, sensitivity, reproducibility and robustness of the Powertap (PWT), Stages (STG) and Garmin Vector (VCT) power meters in comparison with the SRM device. Methods: A national-level male competitive cyclist was required to complete three laboratory cycling tests that included a sub-maximal incremental test, a sub-maximal 30-min continuous test and a sprint test. Two additional tests were performed: the first on vibration exposures in the laboratory and the second in the field. Results: The VCT provided a significantly lower 5 s power output (PO) during the sprint test with a low gear ratio compared with the POSRM (-36.9%). The POSTG was significantly lower than the POSRM within the heavy exercise intensity zone (zone 2, -5.1%) and the low part of the severe intensity zone (zone 3, -4.9%). The POVCT was significantly lower than the POSRM only within zone 2 (-4.5%). The POSTG was significantly lower in standing position than in the seated position (-4.4%). The reproducibility of the PWT, STG and VCT was similar to that of the SRM system. The POSTG and POVCT were significantly decreased from a vibration frequency of 48 Hz and 52 Hz, respectively. Conclusions: The PWT, STG and the VCT systems appear to be reproducible, but the validity, sensitivity and robustness of the STG and VCT systems should be treated with some caution according to the conditions of measurement

Morphology of metallic foams synthetized by plasma electrolysis deposition

International audienceThe aim of our work is to understand the mechanism governing the growth of metallic foams synthetized by plasma electrolysis deposition. This paper reports the influence of the applied voltage on the morphology and microstructure of copper and gold foams. The evolution of strands morphology and size is investigated by field emission scanning electronic microscopy (FE-SEM). The role of the voltage in the growth of metallic foams is then discussed. Finally, the crystalline structure of the strands is determined by transmission electronic microscopy (TEM) and selected area electron diffraction

Influence of standing position on mechanical and energy costs in uphill cycling

International audienceThis study was designed to examine the influence of standing position (vs. seated) during uphill cycling on both mechanical cost (MC) and energy cost (EC) in elite cyclists. For the study, thirteen elite cyclists (VO2max: 71.4 ± 8.0 ml·min−1·kg−1) performed, in a randomised order, three sets of exercises. Each set comprised 2 min of exercise, alternating every 30 s between seated and standing postures, using different slopes and intensity levels on a motorised treadmill. MC was calculated from the measurement of power output and speed, whereas EC was calculated from the measurement of oxygen consumption and speed. MC was significantly higher (+4.3%, p < 0.001) in standing position compared to seated position when all slopes and intensities were considered. However, EC was not significantly affected by the change in position. The standing position also induced a significant increase in rolling resistance power (p < 0.001), rolling resistance coefficient (p < 0.001) and lateral sways (p < 0.001). The significant increase in MC observed in standing position was due to a higher rolling resistance induced by bicycle sways and a shift forward of the centre of mass compared to seated position. This result should lead bicycle tire manufacturers to reduce the increase in rolling resistance between the two positions. Considering the relationship observed between the MC and bicycle sways, cyclists would be well advised to decrease the bicycle sways in order to reduce the MC of locomotion

Effects of recovery using contrast water therapy or compression stockings on subsequent 5-min cycling performance

International audienceMany researchers have investigated the effectiveness of contrast water therapy (CWT) or compression stockings (CS) during recovery, using subsequent performance as the principal outcome measure. However, data in the literature are contradictory, mainly because of the methodology used. Purpose: Based on well-controlled performance measures, this study aimed to compare the effects of CWT, CS or passive recovery (PR) on subsequent performance. Methods: After inclusion based on reproducibility criteria (intra-participant variability in performance test lower than the expected differences between the recovery interventions, i.e. 1.5%), 12 competitive male cyclists (peak power output: 5.0 ± 0.2 W/kg; cycling practice: 4.9 ± 0.4 times/week; intra-participant variability: 1.2 ± 0.2%) came to the laboratory three times in a random crossover design. Each time visit, they performed a tiring exercise on a cycle ergometer, followed by a 5-min performance test during which the mean power output was recorded, separated by a 15-min recovery period during which a 12-min PR, CWT (1:2 (cold: 10-12°C to warm: 36-38°C) min ratio) or CS (~20 mmHg) was implemented. Results: Compared with PR (353.8 ± 13.1 W), performance was significantly higher after CWT (368.1 ± 12.3 W) and CS (360.5 ± 14.8 W). Moreover, performance was significantly higher after CWT than after CS. Conclusion: Athletes can use this information as a way of improving their performance in competition format using repeated high-intensity exercises in a short period of time, such as in mountain bike, track or BMX races. Moreover, these data reinforce interest for researchers to consider performance tests with high test-retest reproducibility, especially when small but real benefits are expected

Wearable multi-sensor system for embedded body position and motion analysis during cycling View publication stats View publication stats

International audiencePurpose: The purpose of this study was to validate the AREM system in laboratory conditions. AREM is an embedded electronic system for motion tracking and movement analysis, based on Micro Electro Mechanical Systems (MEMS) sensors and a reconfigurable hardware/software electronic architecture including FPGA + PSoC embedded boards for real time acquisition and signal processing. Methods: AREM sensors were installed on cyclist before performing on a test in which other measurements were made to analyse efficiency of standing position. The position of cyclists during whole test was measured by both AREM and a Kinematic Arm and verified by video systems. The protocol included 13 elite participants on a motorised treadmill with their own bike during which they rode in a randomized order seated vs. standing positions with several slopes (5, 7.5 and 10%) and intensities (3.8, 4.2 and 4.6 W.kg-1). GE was calculated for each condition using the ratio of power output (PO) measured with a Powertap G3 hub (CycleOps, Madison, USA) and the oxygen uptake (VO2) measured with a portable gas analyzer (Metamax 3B, Cortex, Leipzig, Germany). Results & Discussion: The synchronised data of 8 inertial sensors was retrieved and combined to obtain joint positions of shoulders (2), waist (3), middle and lower trunk (2) on cyclist. 1 sensor was installed under the saddle of the bike. The position data was compared between the two systems, and result on validation of AREM for 3-axis displacements (up to 40cm on X axis). We also compared the accelerations (+/-2 m.s-2 seated to +/-6 m.s-2 in standing position, errors up to 10% between both systems), power and energies for each cyclist during test steps (kinetic energies variation from 1.1 J/Kg to 3 J/Kg in a pedal stroke). Moreover, the acceleration and orientation data on cyclist and bike revealed different approaches on effort management during the test, and were compared to videos to obtain sensors data according to different "standing position" techniques. This data is an interesting indicator of the cyclist fatigue during a test, and is being crossed with PO and VO2 data. Conclusion: The validation of AREM system offers the possibility to extend our measures on real cycling locomotion in outdoor conditions, replacing the kinematic arm with AREM. Despite the 3D movement analysis of the cyclist on a standard protocol, first results suggest a position adjustment according to the technique of each cyclist, but also an impact of the mechanical response of the system tires-bike frame. The main perspective of these works is to include the Structure Health Monitoring analysis (SHM) on bike and to synchronise it with the cyclist activity and motion analysis during outdoor training. With both data, we expect to develop a reliable monitoring and optimisation system of the bike-cyclist couple in different course conditions