INFLUENCE OF CYCLIST SADDLE SETBACK ON KNEE JOINT FORCES

Despite the rapid development of bike fitting services, there is still a lack of scientific evidence on the effects of specific bicycle’s parameters on overuse injuries. The aim of this study was to investigate the influence of saddle setback on knee joint forces. Eleven cyclists experimented three saddle setback conditions while pedaling at a steady power output of 200 W and a cadence of 90 rpm. Using a static optimization procedure based on a musculoskeletal model, we estimated knee joint forces. As a first verification step, our preliminary results showed great similarity between muscle activations estimated from the modeling and experimental data (EMG) especially for the knee extensor muscles. Secondly, tibiofemoral joint forces tend to show that a forward sitting position increases tibiofemoral joint shear forces

A MUSCULOSKELETAL MODELLING APPROACH OF ILIOTIBIAL BAND SYNDROME IN CYCLING. IMPLICATIONS FOR INJURY PREVENTION.

The aim was to investigate the potential risk of developing iliotibial band syndrome (ITBS) through the analysis of the theoretical interaction between joint degrees of freedom and individual pedalling techniques. Experimental lower limb kinematics recorded from ten well-trained healthy cyclists served as input data of a musculoskeletal modelling to calculate the compression force between ITB and the lateral femoral epicondyle (LFE). Cyclists pedalled in a standardized position at a steady state (90rpm and 200W). Results demonstrated that ITBS potential risk increases in individuals whose pedalling technique exacerbate hip extension-adduction and/or knee extension-internal rotation. Furthermore, hip joint kinematics had a greater influence than knee joint angles. This simulation approach could be advantageously implemented as an additional tool to help diagnose and correct potentially harmful sport techniques and optimise equipment setup or design

LOWER LIMB MUSCLE LENGTHS IN ROWING: A PRELIMINARY STUDY

This study aimed to characterise the lower limb muscular coordination in rowing. A musculoskeletal model was developed to be used for movements exhibiting large joints range of motion. Maximum static muscle lengths computed from five static stretching tests were compared with muscle lengths extracted while rowing. Muscle lengths were derived from lower limb kinematics collected using a motion analysis system. Our results showed that classical stretching tests were suitable for a muscle group but must be more specific to target isolated muscle. During rowing trials, bi-articular muscle patterns were subject-dependant with hamstring lengths close to their maximum lengths. Asymmetries were observed for few muscles. Further studies are necessary to confirm these promising findings that may maximise rowing performance and minimise rowing injuries

SLIDING ON HARDCOURT SURFACE WITH SPECIFIC SHOES, PRELIMINARY RESULTS

The purpose of this study was to investigate the sliding characteristics of a new shoe (NSh) concept. The NSh has been developed with the specific aim of facilitating sliding on hard surface such as tennis players can do on clay or synthetic turf. Five young tennis players performed several trials on a walkway instrumented with seven force platforms synchronized with a motion capture system. Results revealed that the coefficient of friction was still higher for the NSh-hard surface condition than for the regular shoesynthetic turf condition but the players were able to obtain the same sliding length provided that approach velocity was higher

Analyse de sensibilité à des changements morphologiques du complexe de l’épaule : application aux gestes de percussion au cours de débitage oldowayen

Si la fabrication et l’utilisation d’outils lithiques ont incontestablement joué un rôle déterminant dans l’évolution des hominines, l’impact de tels comportements sur leur morphologie semble moins faire consensus. Toutefois, il semble que l’architecture et les proportions du complexe de l’épaule chez les premiers représentants du genre Homo aient pu avoir été contraintes par ces comportements. Afin de discuter des potentiels avantages adaptatifs de ces traits morphologiques dans le cadre de ..

Biomechanical modelling of the hand to estimate musculoskeletal constraints during thumb-index finger pinch grip

La préhension manuelle est une des habilités de l’homme la plus développée et la plus utilisée dans la vie de tous les jours. Cette capacité nous permet de saisir et de manipuler des objets dans des configurations aussi nombreuses que complexes. Malheureusement, la main est aussi le siège de nombreuses blessures qui, de par l’importance de la préhension, sont fortement handicapantes. Face à ce constat, comprendre les contraintes mécaniques qui sont exercées dans les muscles, les tendons, les articulations et les ligaments lors de gestes de la vie quotidienne apparaît comme un enjeu majeur pour la prévention, la réhabilitation et l’ergonomie. L’objectif de ce travail doctoral était de développer un modèle biomécanique de la préhension permettant une estimation de ces variables non mesurables. A titre d’exemple,le paradigme de la pince pouce-index a été utilisé. Dans une première étude, les modèles biomécaniques de la pince disponibles dans la littérature ont été développés et comparés.Suite à cette évaluation, il a été constaté que ces modèles, en particulier le pouce,nécessitaient des améliorations pour permettre une évaluation physiologiquement réaliste lors de la préhension. Dès lors, plusieurs améliorations ont été proposées. Premièrement, une procédure expérimentale a été développée afin d’évaluer et d’inclure les participations mécaniques passives (ligaments, tissus mous, butées osseuses) de l'articulation trapèzométacarpienne. Deuxièmement, des mesures effectuées par IRM ont été utilisées afin d’intégrer l’action mécanique du muscle First Dorsale Interosseous dans l’équilibre du pouce,ce muscle étant alors négligé malgré son importance dans les tâches de préhension.Troisièmement, une méthode expérimentale permettant d’évaluer plus facilement et plus précisément, in situ, les axes de flexion/extension et d’adduction/abduction de l’articulation trapèzométacarpienne a été proposée et évaluée. Enfin, le modèle biomécanique incluant ces améliorations a été mis en œuvre dans une dernière étude ergonomique visant à étudier l’effet de la taille de l’objet manipulé sur les forces musculaires et articulaires.Manual precision grip is one of man's most developed and most used ability in everyday lifeactivities. The negative outcome is the high exposure of the hand to repetitive stress injurieswhich are often very disabling. Thus, the understanding of the mechanical stress exerted inmuscles, tendons, joints and ligaments during gripping tasks appears as a major issue forinjury prevention, rehabilitation and ergonomic considerations. This doctoral work aimed atdeveloping a biomechanical model of the grip to estimate the unmeasurable internal loads. Asan example, the classical paradigm of the thumb - index finger grip was used. In a first study,the biomechanical models of the thumb available in the literature were compared and severalimprovements proposed in order to obtain more physiologically realistic predictions. First, anexperimental method was developed to evaluate and include passive structures moment intothe equilibrium of the trapeziometacarpal joint (TMC). Secondly, MRI was used to integratethe mechanical action of the First Dorsal Interosseous muscle at the TMC, since this musclehas commonly been neglected in thumb models but seems essential during pinch grip.Thirdly, the kinematic model which has to be used with the anthropometric data of tendonmoment arms was evaluated and compared to our proposition of a functional method toassess, in situ, the axes of rotation of the TMC. Finally, the biomechanical model includingthese improvements was implemented in an ergonomic study. We investigated the effect ofobject width on grip forces and muscles/joints loads. This doctoral work finds its consistencyin its desire to develop and apply the biomechanical modelling of the hand in the fields ofclinical and ergonomics

Iliotibial Band Syndrome in Cycling : A Combined Experimental-Simulation Approach for Assessing the Effect of Saddle Setback

International audienceBackground: Despite abundant literature, the treatment of iliotibial band syndrome (ITBS) in cyclists remains complicated as it lacks evidence-based recommendations. Purpose: The aim of this study was to develop a musculoskeletal modelling approach that investigates three potential biomechanical determinants of ITBS (strain, strain rate and compression force) and to use this approach to investigate the effect of saddle setback. Design: Cross-sectional Methods: An existing 3D lower-body musculoskeletal model was adapted to cycling and to the computation of three putative pathomechanisms responsible for ITBS: ITB strain, ITB strain rate, and compression force between ITB and the lateral femoral epicondyle (LFE). Lower limb kinematics recorded from ten welltrained healthy cyclists served as input data of the model. Cyclists pedalled at a steady state (90rpm and 200W) on an ergometer, and three different saddle setback conditions were tested. The theoretical combined influence of hip and knee joint angles on ITBS was investigated and analysed through the lens of individual pedalling technique. Results: ITB-LFE compression force was the only parameter significantly affected by saddle setback and supports the hypothesis that compression force is likely to be a determinant factor in ITBS etiology. Furthermore, results showed that ITB-LFE compression force increases in individuals whose pedalling technique exacerbates hip extension-adduction and/or knee extension-internal rotation. Conclusion: This approach has the potential to be advantageously implemented as an additional tool to help diagnose/correct potentially harmful sport techniques and optimize equipment setup/design

Influence of saddle setback on knee joint forces in cycling

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Effect of Object Width on Muscle and Joint Forces During Thumb-Index Finger Grasping

International audienceThe objective of this study was to identify the impact of modifying the object width on muscle and joint forces while gripping objects. The experimental protocol consisted to maintain horizontally five objects of different widths (3.5, 4.5, 5.5, 6.5, and 7.5 cm) with a thumb-index finger grip. Subjects were required to grasp spontaneously the object without any instruction regarding the grip force (GF) to apply. A biomechanical model of thumb-index finger pinch was developed to estimate muscle and joint forces. This model included electromyography, fingertip force, and kinematics data as inputs. The finger joint postures and the GF varied across the object widths. The estimated muscle forces also varied significantly according to the object width. Interestingly, we observed that the muscle force/GF ratios of major flexor muscles remain particularly stable with respect to the width whereas other muscle ratios differed largely. This may argue for a control strategy in which the actions of flexors were preserved in spite of change in joint postures. The estimated joint forces tended to increase with object width and increased in the distal-proximal sense. Overall, these results are of importance for the ergonomic design of handheld objects and for clinical applications

Kinematics of the lumbar muscles in rowing: a preliminary study

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