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See detailGender effect on the scapular 3D posture and kinematic in healthy subjects
Schwartz, Cédric ULg; Croisier, Jean-Louis ULg; Rigaux, Elise et al

in Clinical Physiology and Functional Imaging (in press)

Populations considered for shoulder analysis are often composed of various ratios of men and women. It is consequently hypothesized that gender has no significant effect on the joint kinematic. However ... [more ▼]

Populations considered for shoulder analysis are often composed of various ratios of men and women. It is consequently hypothesized that gender has no significant effect on the joint kinematic. However the literature reports, for the shoulder, differences in the range of motion between genders. The specific influence of gender on the scapula-thoracic kinematics has not been studied yet. The dominant shoulder of two populations of men and women composed of 11 subjects each were evaluated in three dimensions for three distinct motions: flexion in the sagittal plane, abduction in the frontal plane and gleno-humeral internal/external rotation with the arm abducted at 90°. Posture, kinematics and range of motion were studied separately. For flexion and abduction and with regard to the scapular kinematic, external rotation were significantly larger for women than men. The differences were of at least 5° at 120° of humeral elevation. Upward rotations were identical. Women also showed larger average active humero-thoracic range of motion. The mean differences were of 13°, 7°, 12° and 5° for abduction, flexion, internal rotation and external rotation, respectively. No difference was observed between the scapular resting positions of both populations. The observed differences concerning both the scapular and humeral patterns would indicate that the shoulder behavior of men and women should not be expected to be similar. [less ▲]

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See detailLaboratory of Human Motion Analysis - working with high level athletes
Schwartz, Cédric ULg

Conference given outside the academic context (2014)

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See detailInfluence of players' level on racket speed and ball accuracy in the tennis serve
Tubez, François ULg; Croisier, Jean-Louis ULg; Cordonnier, Caroline ULg et al

Conference (2014, July 06)

INTRODUCTION Serve in modern tennis game is an important offensive weapon for players (1-2). In kinematic analysis, serve is the most studied stroke of this game. The aim of our study was to compare the ... [more ▼]

INTRODUCTION Serve in modern tennis game is an important offensive weapon for players (1-2). In kinematic analysis, serve is the most studied stroke of this game. The aim of our study was to compare the performance of two specific populations: international players versus national players. In particular, racket speed at impact and accuracy of ball were assessed. METHODS A tennis court was reconstructed in a motion analysis laboratory. The position of the racket was evaluated in 3D at a frequency rate of 200 Hz. Tests were performed on 6 professional players (international level) and 9 non-professional players (national level). Each of them served 25 trials in direction of the “T” area of deuce diagonal. Two squares of 1m² and 2 m² respectively were delimited on the corner of the serve square. The instruction for both groups was to serve in the “T” area with the highest ball speed and minimal ball rotation (flat serve). RESULTS Although the forward speed of the racket at impact was identical between the two groups of players (International 36.35 ± 2.37 m/s and national 36.37 ± 2.90 m/s, p-value 0,991), the accuracy and consistency of serves on the target area is better for international players group (1m² area: International 33% ± 7% and national 14% ± 12%, p-value 0.0053; 2m² area (including 1m² area): International 71% ± 8% and national 54% ± 12%, p-value 0.0096; Out of zone: International 29% ± 8% and national 46% ± 12%, p-value 0.014). DISCUSSION High-velocity ball seems to be a key factor for serve performance (3). It is known that there is a relationship between racket speed and ball velocity (4). Both groups have high racket speed. However, international players serve with better accuracy and consistency than national players. We hypothesize that these differences are due to capacity of international players to adapt to a particular environment. Moreover, international players could give priority to consistency over velocity. We conclude that high-velocity serve is not a sufficient criterion to perform at international level; consistency and accuracy are two important factors to reach this level. [less ▲]

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See detailImportance of quantitative return-to-field criteria
Schwartz, Cédric ULg; Cordonnier, Caroline ULg; Lehance, Cédric ULg et al

Conference (2014, July 04)

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See detail3D analysis and determination of stride parameters for different type of foot strike in running
Deflandre, Dorian ULg; Bury, Thierry ULg; Schwartz, Cédric ULg et al

Poster (2014, July)

The purpose of the study was to compare methods for the determination of foot strike and toe off for runners with different foot strike patterns. A 3D optoelectronic system usually used in motion ... [more ▼]

The purpose of the study was to compare methods for the determination of foot strike and toe off for runners with different foot strike patterns. A 3D optoelectronic system usually used in motion laboratories was compared with tools commonly used on the field: an optical based detection system (OptoGait) and an accelerometer based system (Myotest). [less ▲]

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See detailExperimental Study of the Human Ability to Deliberately Excite a Flexible Floor
Schwartz, Cédric ULg; Berger, Alexis; Bruls, Olivier ULg et al

in Zingoni, Alphose (Ed.) Proceedings of the 5th International Conference on Structural Engineering, Mechanics and Computation (2014)

Human-structure interactions are not completely understood yet. This paper presents an experimental study focusing on the interaction between a human and a flexible support, with a major aim to better ... [more ▼]

Human-structure interactions are not completely understood yet. This paper presents an experimental study focusing on the interaction between a human and a flexible support, with a major aim to better understand how the behavior of a human subject, bouncing on a flexible structure, adapts to the support motion. Exploratory experiments are undertaken with a 7m-span timber footbridge tested in the Human Motion Analysis Laboratory of the University of Liege. The movements of the coupled system composed of the subject and the footbridge are recorded by Motion Capture technology; the subject\textquoteright{}s 3-D body motion is defined by three important angles: ankle, knee and hip. The interaction between the subject and the footbridge is also quantified by means of force platform measurements. The experiments indicate an influence of the support amplitude and natural frequency on the phase shift between the oscillatory floor motion and the three angles characterizing the motion. [less ▲]

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See detail3D analysis of gait using accelerometer measurements
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Stamatakis, Julien et al

Scientific conference (2013, November 07)

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See detailReference populations for shoulder studies should be selected carefully
Schwartz, Cédric ULg; Denoël, Vincent ULg; Bruls, Olivier ULg et al

Conference (2013, August 06)

To assess various shoulder pathologies / treatments, non pathological populations are often used as references. However, some factors may influence significantly the scapular kinematics within a healthy ... [more ▼]

To assess various shoulder pathologies / treatments, non pathological populations are often used as references. However, some factors may influence significantly the scapular kinematics within a healthy population and consequently alter the final kinematic evaluation. Results of 3D shoulder assessment found in this study show that small (≈5°) but significant differences exist between gender and between the dominant and non-dominant arms. Therefore the populations used for referential data should be selected carefully. [less ▲]

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See detailValidation of an accelerometer-based approach to quantify gait events
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Stamatakis, Julien et al

Poster (2013, June)

Researchers rarely provide solid performance and validation information about their acceleometer-based approaches to human gait analysis. We present here a novel signal processing and analysis algorithm ... [more ▼]

Researchers rarely provide solid performance and validation information about their acceleometer-based approaches to human gait analysis. We present here a novel signal processing and analysis algorithm that automatically extracts four consecutive fundamental events of walking: heel strike (HS), toe strike (TS), heel off (HO), and toe off (TO). In addition, we validate this accelerometer-based technique by comparing these extracted gait events with those obtained by a kinematic 3D analysis system and a force plate, used as gold standards. [less ▲]

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See detailL'apport de l'analyse biomécanique 3-D dans les stratégies préventives à partir de 2 exemples
Schwartz, Cédric ULg; Croisier, Jean-Louis ULg; Tubez, François ULg et al

in Julia, M; Croisier, Jean-Louis; Perrey, S (Eds.) et al Prévention des troubles musculo-squelettiques chez le sportif (2013)

De nouveaux outils de mesure permettent de quantifier la cinématique et la dynamique articulaire fonctionnelle des athlètes (systèmes optoélectroniques 3D, plateforme de forces, électromyographie, …). Ces ... [more ▼]

De nouveaux outils de mesure permettent de quantifier la cinématique et la dynamique articulaire fonctionnelle des athlètes (systèmes optoélectroniques 3D, plateforme de forces, électromyographie, …). Ces données sont importantes dans le sens où elles donnent à l’équipe médicale et sportive des informations objectives sur le geste du sportif dans sa pratique réelle. Elles favorisent la compréhension et l’amélioration de la performance ainsi que la prévention lésionnelle et la détection de situations à risque. Dans le cadre d’un suivi longitudinal des sportifs, ces mesures sont intéressantes pour mettre en place des critères objectifs et spécifiques à l’athlète de retour sur le terrain après une blessure. Ce document a pour objectif de présenter les principaux outils disponibles dans les laboratoires de biomécanique et d’illustrer leurs utilisations à travers 2 exemples : l’influence de la raideur de l’épaule sur la mobilité de l’épaule et l’analyse cinématique du service au tennis. [less ▲]

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See detailMerging multi-camera data to reduce motion analysis instrumental errors using Kalman filters
Schwartz, Cédric ULg; Denoël, Vincent ULg; Forthomme, Bénédicte ULg et al

in Computer Methods in Biomechanics and Biomedical Engineering (2013)

In motion capture systems, markers are often seen by multiple cameras. All cameras do not measure the position of the markers with the same reliability because of environmental factors such as the ... [more ▼]

In motion capture systems, markers are often seen by multiple cameras. All cameras do not measure the position of the markers with the same reliability because of environmental factors such as the position of the marker in the field of view or the light intensity received by the cameras. Kalman filters offer a general framework to take the reliability of the various cameras into account and consequently improve the estimation of the marker position. The proposed process can be applied to both passive and active systems. Several reliability models of the cameras are compared for the Codamotion active system, which is considered as a specific illustration. The proposed method significantly reduces the noise in the signal, especially at long range distances. Therefore, it improves the confidence of the positions at the limits of the field of view. [less ▲]

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See detailDominance effect on scapula 3-dimensional posture and kinematics in healthy male and female populations
Schwartz, Cédric ULg; Croisier, Jean-Louis ULg; Rigaux, Elise et al

in Journal of Shoulder and Elbow Surgery (2013), (0), -

Background: The contralateral shoulder is often used as a reference when evaluating a pathological shoulder. However literature provides contradictory results regarding the symmetry of the scapular ... [more ▼]

Background: The contralateral shoulder is often used as a reference when evaluating a pathological shoulder. However literature provides contradictory results regarding the symmetry of the scapular pattern in a healthy population. We assume that several factors including the gender and the type of motion may influence the scapula bilateral symmetry. Method: The dominant and non dominant shoulders of two populations of men and women composed of 11 subjects each were evaluated for three distinct motions: flexion in the sagittal plane, abduction in the frontal plane and gleno-humeral internal/external rotation with the arm abducted at 90°. Posture, kinematic and range of motion were studied separately. Results: Asymmetries are observed for motions performed in the frontal and sagittal plane but not for the internal/external rotation with the arm abducted at 90°. Multiplane asymmetries are observed for the male population, whereas asymmetries for the female one are mainly uniplanar. For both men and women, the scapula has a larger upward rotation on the dominant side. For men, a larger posterior tilt is also observed. The asymmetries mainly originate in the scapula kinematic and not in its original posture. Discussion: Even if the asymmetries are not large in terms of amplitude (inferior to 5°), one should be aware of their existence and the influence of the composition of the studied population when using the contralateral shoulder as a reference. [less ▲]

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See detailUsing merged kinematic and anatomical data to evaluate humeral motion estimation: a pilot study
Schwartz, Cédric ULg; Leboeuf, Fabien; Rémy-Néris, Olivier et al

in Computer Methods in Biomechanics and Biomedical Engineering. Imaging & Visualization (2013)

Optoelectronic systems are widely used in 3D motion capture. However, the reliability of the motion estimation depends on soft tissue artifacts and should therefore be validated. Two different sets of ... [more ▼]

Optoelectronic systems are widely used in 3D motion capture. However, the reliability of the motion estimation depends on soft tissue artifacts and should therefore be validated. Two different sets of humeral markers were studied on four subjects. Anatomical and kinematic measurements were combined and the plausibility of the relative position of the bones in the glenohumeral joint during motion was evaluated using a new coherence index. Our findings show that an identical protocol leads to a large variability of the articular coherence for the subjects. However the use of an extra marker on the distal part of the humerus improves the humeral kinematics for three of the four subjects. Scientists and clinicians using 3D systems should remain aware of the influence of subject-specific morphology on the accuracy of the measure. Differences with a reference group may come from clinical reasons but also from measurement errors due to the inter-individual morphological differences. [less ▲]

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See detailShoulder injury prevention in sports using 3D motion capture
Schwartz, Cédric ULg; HAZEE, Amandine ULg; Denoël, Vincent ULg et al

Poster (2012, December 07)

In sports, where regular and intensive training could progressively lead to traumatic situations, accurate measurement of kinematic parameters can help to predict and anticipate injuries. Overhead ... [more ▼]

In sports, where regular and intensive training could progressively lead to traumatic situations, accurate measurement of kinematic parameters can help to predict and anticipate injuries. Overhead throwing athletes may develop an increased stiffness of the shoulder capsule. The resulting diminution of the gleno-humeral range of motion is usually associated with decreased performance and injury risks. This study illustrates the detection of these situations that put the athlete at risk. [less ▲]

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See detailValidated Extraction of Gait Events from 3D Accelerometer Recordings
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Stamatakis, Julien et al

in IEEE International Conference on 3D Imaging (IC3D) (2012, December)

This work is part of a project that deals with the three-dimensional (3D) analysis of normal and pathological gaits based on a newly developed system for clinical applications, using low-cost wireless ... [more ▼]

This work is part of a project that deals with the three-dimensional (3D) analysis of normal and pathological gaits based on a newly developed system for clinical applications, using low-cost wireless accelerometers and a signal processing algorithm. This system automatically extracts relevant gait events such as the heel strikes (HS) and the toe-offs (TO), which characterize the stance and the swing phases of walking. The performances of the low-cost accelerometer hardware and related algorithm have been compared to those obtained by a kinematic 3D analysis system and a force plate, used as gold standard methods. The HS and TO times obtained from the gait data of 7 healthy volunteers (147 trials) have been found to be (mean ± standard deviation) 0.42±7.92 ms and 3.11±10.08 ms later than those determined by the force plate, respectively. The experimental results demonstrate that the new hardware and associated algorithm constitute an effective low-cost gait analysis system, which could thus be used for the assessment of mobility in routine clinical practice. [less ▲]

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See detailAnalyse de la position en 3 dimensions : intérêts pour la posturologie
Schwartz, Cédric ULg

Conference (2012, January 29)

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See detail3D Analysis of Normal and Pathological Gait Based on Low-Cost Wireless Accelerometers
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Bruls, Olivier ULg et al

in URSI Benelux Forum 2012 “Antennas: multiple designs, multiple applications” (2012)

We describe the principle and use of a new low-cost, wireless, 3-axis accelerometer-based device that records acceleration signals and automatically analyses them to characterize normal and pathological ... [more ▼]

We describe the principle and use of a new low-cost, wireless, 3-axis accelerometer-based device that records acceleration signals and automatically analyses them to characterize normal and pathological gait. [less ▲]

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See detailDetection of incoherent joint state due to inaccurate bone motion estimation
Schwartz, Cédric ULg; Leboeuf, Fabien; Rémy-Néris, Olivier et al

in Computer Methods in Biomechanics & Biomedical Engineering (2011)

In biomechanical modeling and motion analysis, the use of personalized data such as bone geometry would provide more accurate and reliable results. However, there is still a limited number of tools used ... [more ▼]

In biomechanical modeling and motion analysis, the use of personalized data such as bone geometry would provide more accurate and reliable results. However, there is still a limited number of tools used to measure the evolution of articular interactions. This paper proposes a coherence index to describe the articular status of contact surfaces during motion. The index relies on a robust estimation of the evolution of surfacic interactions between the joint surfaces. The index is first compared to distance maps on simulated motions. It is then used to compare two motion capture protocols (two different localizations of the markers for scapula tracking). The results show that the index detects progressive modifications in the joint and allows to distinguish the two protocols, in accordance with the literature. In the future, the index could, among other things, be used to compare / improve biomechanical models and motion analysis protocols. [less ▲]

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