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1

Computerized static posturography and laterality in children : Influence of age

Bourelle S., Dey N., Sifaki-Pistolla D., Berge B., Gautheron V., Cottalorda J., Taiar R.

Acta of Bioengineering and Biomechanics

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2017

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Vol. 19, no. 2

129--139

EN

The present study aims to explore relationships between footedness and posturographic assessment in children aged from 4 to 10. A real-time computerised device was used on a force plate for movement analysis. It requires a static posturography to assess postural control of children with the same handedness and footedness. Methods: Thirty eight right-handed and right-footed children organized in three age groups of 4 to 6 years old, 6 to 8 years old and 8 to 10 years old participated in the study. Two statical tests, the Unilateral Stance (US) and the Weight Bearing Squat (WBS) were performed, jointly with a dynamic balance examination (Limits of Stability (LOS)). All these tests were executed to explore the body capability of the right/left side. Results: The study demonstrated significant differences involving the right/left side among the three age groups. Better performance on the youngest children’s right part and on the oldest children’s left part was observed. Differences between the left and right sides of the body were noticeably revealed by posturographic assessments in right-handed and right-footed children. Conclusions: Age seemed to be a determinant for these outcomes. Maturation of the vestibular at the ages of 6 or 7 years might explain the observed differences between the youngest children and older-children.

2

Impact of multi-task on symptomatic patient affected by chronical vestibular disorders

Regrain E., Regnault P., Kirtley Ch., Shamshirband S., Chays A., Boyer F.-C., Taiar R.

Acta of Bioengineering and Biomechanics

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2016

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Vol. 18, no. 3

123--129

EN

Purpose: After a vestibular deficit some patients may be affected by chronical postural instability. The aim of this study was to identify the emotional and cognitive factors of these symptomatic patients. In particular, the double cognitive task and the anxiety disorder were identified by our patients. Through a retrospective study, 14 patients (65.4 ±18 years) participated in the experiment. Method: The experimentation consists in the study of the standing position of our patients through the aggregate of the trajectories of the center of pressure (COP) using a force plate device. With the aim of isolating the emotional and cognitive influence, this experimentation was defined in two conditions. In the first one, the patients were asked to maintain their balance without additional tasks. In the second one, the patients were submitted to an additional cognitive arithmetic task. The stabilogram surface, length (the forward and backward displacement distance during deviations in COP), lateral and the antero-posterior deviations were assessed. Results: Our results showed an increase of postural instability of patients affected by chronical vestibular disorders when submitted to the double task. The patients submitted to the cognitive task present a larger surface of activity in comparison with the free-task one (Wilcoxon test p-value equals p = 0.0453). In addition, their displacements inside this area are more important (p = 0.0338). The COP of all our patients deviated forward in the presence of the double task. Conclusion: The increase in instability during the double cognitive task could be explained by an additional stress caused by the desire to make a success of the cognitive task.

3

Finite element modelling of the articular disc behaviour of the temporo-mandibular joint under dynamic loads

Jaisson M., Lestriez P., Taiar R., Debray K.

Acta of Bioengineering and Biomechanics

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2011

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Vol. 13, no. 4

85-91

EN

The proposed biodynamic model of the articular disc joint has the ability to affect directly the complete chewing mechanism process and its related muscles defining its kinematics. When subjected to stresses from the mastication muscles, the disc absorbs one part and redistributes the other to become completely distorted. To develop a realistic model of this intricate joint a CT scan and MRI images from a patient were obtained to create sections (layers) and MRI images to create an anatomical joint CAD model, and its corresponding mesh element using a finite element method. The boundary conditions are described by the external forces applied to the joint model through a decomposition of the maximum muscular force developed by the same individual. In this study, the maximum force was operating at frequencies close to the actual chewing frequency measured through a cyclic loading condition. The reaction force at the glenoid fossa was found to be around 1035 N and is directly related to the frequency of indentation. It is also shown that over the years the areas of maximum stresses are located at the lateral portion of the disc and on its posterior rim. These forces can reach 13.2 MPa after a period of 32 seconds (s) at a frequency of 0.5 Hz. An important part of this study is to highlight resilience and the areas where stresses are at their maximum. This study provides a novel approach to improve the understanding of this complex joint, as well as to assess the different pathologies associated with the disc disease that would be difficult to study otherwise.

4

Analysis of wall shear stress around a competitive swimmer using 3D Navier-Stokes equations in CFD

Popa C.V., Zaidi H., Arfaoui A., Polidori G., Taiar R., Fohanno S.

Acta of Bioengineering and Biomechanics

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2011

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Vol. 13, no. 1

3-11

EN

This paper deals with the flow dynamics around a competitive swimmer during underwater glide phases occurring at the start and at every turn. The influence of the head position, namely lifted up, aligned and lowered, on the wall shear stress and the static pressure distributions is analyzed. The problem is considered as 3D and in steady hydrodynamic state. Three velocities (1.4 m/s, 2.2 m/s and 3.1 m/s) that correspond to inter-regional, national and international swimming levels are studied. The flow around the swimmer is assumed turbulent. The Reynolds-averaged Navier-Stokes (RANS) equations are solved with the standard k-u turbulent model by using the CFD (computational fluid dynamics) numerical method based on a volume control approach. Numerical simulations are carried out with the ANSYS FLUENTŽ CFD code. The results show that the wall shear stress increases with the velocity and consequently the drag force opposing the movement of the swimmer increases as well. Also, high wall shear stresses are observed in the areas where the body shape, globally rigid in form, presents complex surface geometries such as the head, shoulders, buttocks, heel and chest.

5

The influence of swimming type on the skin-temperature maps of a competitive swimmer from infrared thermography

Zaidi H., Taiar R., Fohanno S., Polidori G.

Acta of Bioengineering and Biomechanics

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2007

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Vol. 9, nr 1

47-51

EN

This work aims to study the usability of infrared thermography in swimming for the purpose of quantifying the influence of the swimming style on the cartographies of cutaneous temperatures of a swimmer. Only one subject took part in the experimental protocol, who was to accomplish a 4 × 100 m 4 medley. Thermal acquisitions followed by one period of recovery with return to thermal balance were carried out between particular strokes. IR thermography made it possible to discuss the influence of the swimming style on the distributions of cutaneous temperatures in various body zones. This process seems to be completely adaptable to the development of future statistical studies.

6

Experimental assessment of the drag coefficient during butterfly swimming in hydraulic flume

Taiar R., Bertucci W., Letellier Th., Benkemis I., Toshev Y.

Acta of Bioengineering and Biomechanics

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2005

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Vol. 7, nr 2

98-108

EN

A body when moving in a fluid is to withstand drag that is proportional to the drag coefficient, the frontal surface area, and the square of the body velocity relative to the fluid velocity (VOGEL [14]). The aim of our study was to determine the relationships between the drag coefficient (CD) and the Reynolds number (Re) for a high-level swimmer. In TAIAR et al. [12], three most propulsive butterfly positions have been defined: the end of the external sweep (beginning of the cycle), the end of the internal sweep (middle of the cycle), and the end of the thrust (end of the cycle). These three positions were reproduced using real-size mannequins articulated ui real-velocity conditions. Experiments have been done ui the large-scale hydraulic flume of the University' of Nantes. Two types of the curves CD (Re) were obtained: for the "best swimmer" and for ''other swimmers". Following the swimming of the ex-word champion Pankratov during the World Championship m Rome (1994) the mannequin representing the "best swimmer" has been positioned similarly to the ex-world champion at the beginning, in the middle and at the end of cycle. The body positions of Pankratov have been obtained using the image analysis software Schleihaui 4.0. In order to obtain the curves CD (Re) representing "other swimmers", the body positions of lower-level swimmers have been used at the beginning, in the middle and at the end of swimming cycle. The two types of curves show well the gap between the techniques of the "best swimmer" and "other swimmers". Our study shows the importance of the body position dining the swimming cycle to minimizing the drug and to assuring better propulsion, i.e. better performance. The results show that the most effective swimmers optimise the body positions in order to reduce the frontal surface and therefore to minimize the drag.

7

Estimation of smimmers anthropometric parameters and surface areas in real swimming conditions

Taiar R., Lodini A., Rouard A., Toshev Y.

Acta of Bioengineering and Biomechanics

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2005

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Vol. 7, nr 1

85-95

EN

The main aim of this study was to propose and to test a reliable method allowing us to obtain data both from static numeric images and numeric video images taken in real swimming conditions and using appropriate computer procedure. Based on these images it is possible to estimate the swimmer's anthropometric parameters and the projected frontal surface (PFS) during swimming. Measurements of sportsmen anthropometric parameters, including swimmers, are usually carried out in a static anatomic position using standard anthropometric method. In the present study, this common method is compared with a new approach which enables us to carry out the anthropometric measurements using numeric images collected both in static and in real swimming conditions. This method offers two advantages: the results are obtained in real dynamic conditions and the measurements are characterized by a high precision and repeatability. The proposed measurement approach is suitable also for other applications in the field of biomechanics.

8

Performance modelling of butterfly swimmers: links between morphometric, kinematic and hydrodynamic variables

Taiar R., Toshev Y., Lodini A., Rouard A., Toshev Y.

Acta of Bioengineering and Biomechanics

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2004

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Vol. 6, nr 2

77-88

EN

The aim of the study is to explain the performance of butterfly swimmers over 100 m butterfly using a set of selected morphometric, kinematic and hydrodynamic parameters. Parametric modelling and mul-tivariate analysis are used in order to define synthetic variables (indices) describing kinematic and morphometric parameters. The possibility of predicting the performance V]00 (mean velocity over 100 m butterfly) using morphology variables is tested. The results showed that the parametric model proposed describes well the performance. The selected kinematic parameter X|lip (instantaneous hip displacement) varies little among the swimmers, whereas for the parameter k (describing the variation of the displacement patterns) highly different values have been obtained. Hip displacements vary essentially according to their shapes - high k values corresponding to swimmers acceleration at the end of the cycle, and low k values corresponding to swimmers with more regular displacements. Thus, k was selected as the only parameter to describe the hip displacement patterns. A negative relation between the performance and the hydrodynamic variables has been obtained confirming that every increase of flow resistance get worse performance. A positive relation between the performance and the individual morphological data has been found, i.e. light and sharp swimmers have in general higher performance. No relation between k and the morphology has been observed. On the contrary, a negative relation between the hydrodynamic variables and the morphology has been obtained.