KINETIC ANALYSIS OF DIFFERENT RUNNING STARTS: IMPACT ON FORWARD CENTER OF MASS ACCELERATION AND PERFORMANCE

In this study, three running starts allowing more or less large shifts of the centre of pressure (CoP) were compared in order to assess their impact on the forward acceleration of the centre of mass (CoM) and on the performance of a short distance run. Temporal and biomechanical parameters were calculated from CoP data in eighteen subjects. Our results suggested that an increase of the base of support by moving backward the CoP quickly after the start signal has a positive impact on the performance on short distance runs

Lower Limb Mechanical Properties: Significant References Omitted

International audienceWe read with attention the recent narrative literature review by Pearson and McMahon [1]. We were very surprised and quite disappointed by the amount of relevant literature omitted by the authors on lower limb mechanical properties and, specifically, how ‘limb stiffness’ could affect performance and risk of injury. Although this review focuses on muscle-tendon unit (MTU) stiffness, the more global vertical, leg and joint stiffness (i.e. referred to as limb stiffness, collectively) are also reviewed, as the authors assume that limb stiffness is primarily controlled by MTU stiffness

Syndioselective ring-opening polymerization and copolymerization of trans-1,4-cyclohexadiene carbonate mediated by achiral metal- and organo-catalysts

International audienceThe ring-opening polymerization (ROP) of trans-1,4-cyclohexadiene carbonate (CHDC) has been investigated computationally and experimentally. DFT computations indicate that ring-opening of CHDC is thermodynamically possible, yet to a lesser extent than that of trans-cyclohexene carbonate (CHC). Effective homopolymerizations of rac-CHDC and simultaneous or sequential copolymerizations of rac-CHDC with rac-CHC and L-LA were achieved with a diaminophenolate zinc-based complex ([(NNO)ZnEt]) or a guanidine (TBD) associated with an alcohol. These ROP reactions, which confirmed the lower reactivity of rac-CHDC vs. rac-CHC, especially in homopolymerization, proceeded without any decarboxylation. Quite uniquely, highly syndiotactic PCHDC was obtained from ROP of rac-CHDC with both the zinc- and TBD-based catalysts, as revealed by 13C{1H} NMR studies. The prepared homopolymers and block or random copolymers were characterized by 1H, 13C{1H} NMR, MALDI-ToF MS, SEC and DSC techniques

A simple method for measuring power, force, velocity properties, and mechanical effectiveness in sprint running

International audienceThis study aimed to validate a simple field method for determining force– and power–velocity relationships and mechanical effectiveness of force application during sprint running. The proposed method, based on an inverse dynamic approach applied to the body center of mass, estimates the step-averaged ground reaction forces in runner's sagittal plane of motion during overground sprint acceleration from only anthropometric and spatio-temporal data. Force– and power–velocity relationships, the associated variables, and mechanical effectiveness were determined (a) on nine sprinters using both the proposed method and force plate measurements and (b) on six other sprinters using the proposed method during several consecutive trials to assess the inter-trial reliability. The low bias (<5%) and narrow limits of agreement between both methods for maximal horizontal force (638 ± 84 N), velocity (10.5 ± 0.74 m/s), and power output (1680 ± 280 W); for the slope of the force–velocity relationships ; and for the mechanical effectiveness of force application showed high concurrent validity of the proposed method. The low standard errors of measurements between trials (<5%) highlighted the high reliability of the method. These findings support the validity of the proposed simple method, convenient for field use, to determine power, force, velocity properties, and mechanical effectiveness in sprint running

ETUDE PRELIMINAIRE DE LA PRECISION DE LA MESURE DE LA RECONSTRUCTION 3D DE LA PHASE D'IMPULSION EN DEPART DOS

National audienc

The development and validation of a scoring tool to predict the operative duration of elective laparoscopic cholecystectomy

Background: The ability to accurately predict operative duration has the potential to optimise theatre efficiency and utilisation, thus reducing costs and increasing staff and patient satisfaction. With laparoscopic cholecystectomy being one of the most commonly performed procedures worldwide, a tool to predict operative duration could be extremely beneficial to healthcare organisations. Methods: Data collected from the CholeS study on patients undergoing cholecystectomy in UK and Irish hospitals between 04/2014 and 05/2014 were used to study operative duration. A multivariable binary logistic regression model was produced in order to identify significant independent predictors of long (> 90 min) operations. The resulting model was converted to a risk score, which was subsequently validated on second cohort of patients using ROC curves. Results: After exclusions, data were available for 7227 patients in the derivation (CholeS) cohort. The median operative duration was 60 min (interquartile range 45–85), with 17.7% of operations lasting longer than 90 min. Ten factors were found to be significant independent predictors of operative durations > 90 min, including ASA, age, previous surgical admissions, BMI, gallbladder wall thickness and CBD diameter. A risk score was then produced from these factors, and applied to a cohort of 2405 patients from a tertiary centre for external validation. This returned an area under the ROC curve of 0.708 (SE = 0.013, p  90 min increasing more than eightfold from 5.1 to 41.8% in the extremes of the score. Conclusion: The scoring tool produced in this study was found to be significantly predictive of long operative durations on validation in an external cohort. As such, the tool may have the potential to enable organisations to better organise theatre lists and deliver greater efficiencies in care

A blood atlas of COVID-19 defines hallmarks of disease severity and specificity.

Treatment of severe COVID-19 is currently limited by clinical heterogeneity and incomplete description of specific immune biomarkers. We present here a comprehensive multi-omic blood atlas for patients with varying COVID-19 severity in an integrated comparison with influenza and sepsis patients versus healthy volunteers. We identify immune signatures and correlates of host response. Hallmarks of disease severity involved cells, their inflammatory mediators and networks, including progenitor cells and specific myeloid and lymphocyte subsets, features of the immune repertoire, acute phase response, metabolism, and coagulation. Persisting immune activation involving AP-1/p38MAPK was a specific feature of COVID-19. The plasma proteome enabled sub-phenotyping into patient clusters, predictive of severity and outcome. Systems-based integrative analyses including tensor and matrix decomposition of all modalities revealed feature groupings linked with severity and specificity compared to influenza and sepsis. Our approach and blood atlas will support future drug development, clinical trial design, and personalized medicine approaches for COVID-19

Effets de la fatigue et du niveau d'entraînement : étude des relations entre les coûts énerfétique et mécanique en course à pied

La performance en course d'endurance dépend à la fois des qualité énergétiques et mécaniques du coureur. En effet, le temps mis pour parcourir une distance donnée est fonction du travail mécanique réalisé par les muscles et de l'énergie consommée pour produire ce travail. Au cours du XXème siècle, de nombreux travaux ont mesuré la relation entre le coût mécanique et le coût énergétique de la locomotion. L'étude de cette relation pose de nombreux problèmes d'ordre méthodologique car la mesure du coût mécanique résulte d'une évaluation globale des changements dans les niveaux d'énergie mécanique. L'énergie réellement développée par chaque muscle reste inconnue. Pour contourner ces difficultés méthodologiques, notre approche consiste à mesurer les effets de la modification du coût énergétique sur le coût mécanique, ou inversement. Ce travail a permis de mesurer les effets de la fatigue et du niveau d'entraînement sur les différents composants du coût mécanique (les coûts mécaniques potentiel, cinétique et de gesticulation : Cpot, Ccin, et Cgest) et sur le coût énergétique (C). L'analyse des principaux résultats montre d'une part, que la modification du C induite par la fatigue n'est pas liée à une modification du coût mécanique et d'autre part, que la modification des différentes composantes du coût mécanique suivant le niveau d'entraînement n'est pas en relation avec une amélioration du C. Les modifications des paramètres mécaniques avec la fatigue ou le niveau d'entraînement ne sont donc pas associées à des modification du C. La performance en endureance paraît donc dépendres à la fois de paramères énergétiques et de paramètres mécaniques tels que la variabilités de la fréquence de pas, le déplacement vertical du centre de masse, ou le coût mécanique de gesticulation. Néanmoins, les résultats obtenus dans ce travail ne permettant pas de préciser avec certitude les mécanismes responsables des modifications du coût mécanique, deux hypothèses peuvent être formulées. Les modifications biomécaniques observées pourraient être associées à des modifications des propriétés élastiques des muscles et des tendons, ou à un mécanisme visant à diminuer le choc induit par la pose du pied au sol.EVRY-BU (912282101) / SudocSudocFranceF

Changes in internal mechanical cost during over-ground running to exhaustion

International audiencePurpose: The purpose of this study was to determine, during an overground supra-threshold run, whether a change in the internal mechanical cost could occur during an exhaustive run and whether this change was related to the increase in the energy cost of running (Cr).Methods: The Cr of 14 endurance runners was measured from pulmonary gas exchange using a breath-by-breath portable gas analyzer (Cosmed K4b2, Rome, Italy), at the third and the last minute of an exhaustive exercise performed at their velocity corresponding to 95% of the maximal oxygen uptake (4.88 ± 0.38 m·s−1). At the same time, potential, kinetic, and internal mechanical costs (Cpe, Cke, and Cint) were measured with a 3D motion analysis system (ANIMAN3D).Results: Cint and Cr increased significantly within the third minute and the end of the supra-threshold exercise (respectively, 0.55 ± 0.07 vs 0.60 ± 0.07 J·kg−1·m−1 and 4.10 ± 0.39 vs 4.32 ± 0.42 J·kg−1·m−1; P ≤ 0.03). However, the percentage of variation of Cint and Cr were not correlated (r = 0.06; P = 0.84). Contrary to Cint, Cke and Cpe remained constant during the exercise (respectively, 1.33 ± 0.33 vs 1.38 ± 0.29 J·kg−1·m−1 P = 0.79 and 0.47 ± 0.11 vs 0.48 ± 0.10 J·kg−1·m−1; P = 0.67), but both parameters were significantly correlated with Cr (r = 0.43; P = 0.03 and r = 0.40; P = 0.03).Conclusion: During overground running to exhaustion, a significant increase in Cint occurred, but this did not account for the increase in Cr. Moreover, the increase in Cint has yet to be explained