References of "Schwartz, Cédric"
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See detailReliability of unipodal and bipodal counter movement jump landings in a recreational male population
Schwartz, Cédric ULg; Forthomme, Bénédicte ULg; Paulus, Julien ULg et al

in European Journal of Sport Science (in press)

Movement patterns during landing have been suggested to be related to injury risk. The purpose of this study was to determine the inter-session reliability of kinematic variables and ground reaction ... [more ▼]

Movement patterns during landing have been suggested to be related to injury risk. The purpose of this study was to determine the inter-session reliability of kinematic variables and ground reaction forces during landing in a population of male recreational athletes after a counter movement jump. Both unipodal and bipodal landings were evaluated. Furthermore, the possibility to improve landing reliability with a verbal instruction was also studied. Twenty- four male volunteers with no history of lower-extremity trauma were randomly assigned to two groups (with and without verbal landing instruction). An optoelectronic 3D system and force plates were used to measure the lower-limb joint angles and the ground reaction forces during landing. Intraclass correlation values show moderate to excellent inter-session reliability for the bipodal task (ICC average: 0.80, range: 0.46 to 0.97) and poor to excellent reliability for the unipodal task (ICC average: >0.75, range: 0.20 to 0.95). However, large standard errors of measurement values at the ankle joint at impact (27.6 ± 11.5°) and for the vertical ground reaction forces (394 ± 1091 N) show that some variables may not be usable in practice. The verbal instruction had a negative effect on the reliability of unipodal landing but improved the reliability of bipodal landing. These findings show that the reliability of a landing task is influenced by its motor complexity as well as the instruction given to the subject. [less ▲]

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See detailA Novel Accelerometer-Based Method for Stride Length Estimation
Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg; Denoël, Vincent ULg et al

Poster (2017, July 14)

We demonstrate the feasibility of accurately and precisely estimating the left/right average stride length from measured heel/toe accelerations in the gait of healthy, old adults. Our approach relies on ... [more ▼]

We demonstrate the feasibility of accurately and precisely estimating the left/right average stride length from measured heel/toe accelerations in the gait of healthy, old adults. Our approach relies on (1) a novel method that uses only accelerometer data without the need of additional data from, e.g., gyroscopes and/or magnetometers, and on (2) the validation of the results using reference 3D optoelectronic system data. [less ▲]

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See detailHow much should you jump? Reproducibility evaluation of a 3-dimensional fatigability countermovement jump test
Paulus, Julien ULg; Schwartz, Cédric ULg; Tubez, François ULg et al

Conference (2017, July 02)

Introduction With the stop jump, the counter movement jump (CMJ) is probably the most used jump in sport. In the literature, a number of studies use the counter movement jump to explore (neuro-)muscular ... [more ▼]

Introduction With the stop jump, the counter movement jump (CMJ) is probably the most used jump in sport. In the literature, a number of studies use the counter movement jump to explore (neuro-)muscular fatigability [1-4]. However, due to the continuous [1-3] (or semi-continuous [4]) character of the test, the CMJ become drop jumps from the second one. Nevertheless, the drop jump isn't the most frequent jump type in sport. These evaluations, with (semi-)continuous jumps, don't reflect the sport reality and therefore a more effective (neuro-)muscular jumping fatigability evaluation must be validated. Methods Nineteen volleyball players (23,5 ± 3,3 years, 187,6 ± 6,6 cm, 77,5 ± 8,5 kg), with no history of (major) lower limb injury, submitted to two jumping fatigability tests, with seven days between each session, under the direction of a single researcher. The jumping fatigability tests consists of the repetition of 50 maximal CMJ at the rate of 33bpm. Between each CMJ, the subject were asked to make a full triple-extension and to wait the next auditory and visual signal of the metronome to start the hip-knee-ankle flexion. With these instructions, each jump remains a CMJ. Subjects were asked to leap as high as possible from the first to the last CMJ. The jumping height was recorder for each jump with three dimensional camera. The reproducibility was assessed by Standard Error of Measurement (SEM), Minimal Difference needed to be considered real (MD), Coefficient of Variation (CV), Pearson Correlation Coefficient (PCC) with 95% confidence interval, Effect Size Cohen (ES Cohen) with 90% confidence interval, paired Student's t-test, Intraclass Correlation Coefficient (ICC 2,1) with 95% confidence interval and Magnitude-Based Inferences (MBI). Results The results summary is available in the Table 1. In this table, only few parameters are presented and only for the partial sums of the first 10, 20, 25, 30, 40 and 50 jumps. Our analyses were based on the partial sums per interval of one jump and all statistical tests listed in "Methods" section have been considered. The partial sum with twenty-five CMJ have an excellent reproducibility (MBI with 0/99/1; ICC with 0.961 [0.902/0.985]; ES Cohen with -0.03 [-0.17/0.10]; PCC with 0.966 [0.911/0,987] and p-value < 0.0001). Moreover, it induce a great height decrease (-23%) and its duration (45.5 s) is similar to the recommendation for the knee fatigability isokinetic protocol [5]. MBI (+/trivial/-) Height decrease ICC (2,1) Test duration 10 0/100/0 -12,7% 0.967 18 s 20 0/99/1 -19,0% 0.964 36 s 25 0/99/1 -23,0% 0.961 46 s 30 0/98/1 -25,6% 0.955 55 s 40 0/98/1 -32,1% 0.950 73 s 50 0/98/2 -38,4% 0.943 91 s Table 1: reproducibility statistics results depending on the number of jumps considered (magnitude-based inferences (MBI) with percentage chances of better/trivial/worst retest vs test results; height jump decrease (last jump / better jump); ICC (2,1); test duration). Discussion Because of the (semi-)continuous character of a majority of fatigability jumping test [1-4], our test is the first, at our knowledge, to explore the reproducibility of a strict CMJ jumping fatigability task. Considering the statistical (relative and absolute) reproducibility results, twenty-five maximal CMJ seems to be the best compromise between reliability of the data and physiological interpretability of test's results. Indeed, its (relative and absolute) reproducibility is excellent and it induces a greater height decrease than shorter test while remaining similar in total duration than other fatigability tests which explore the anaerobic lactic system. References 1. Bosco et al, Eur J Appl Physiol Occup Physiol, 51(3):357-364, 1983. 2. Cormack et al., Int J Sports Physiol Perform, 3(2):131-44, 2008. 3. Dal Pupo et al., J Sci Med Sport, 17(6):650-5, 2014. 4. Meckel et al., J Strength Cond Res, 29(8):2122-7, 2015. 5. Bosquet et al., Int J Sports Med, 31(2):82-8, 2010. [less ▲]

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See detailExperimental characterisation of tape spring nonlinear compliant mechanisms
Dewalque, Florence ULg; Schwartz, Cédric ULg; Denoël, Vincent ULg et al

Conference (2017, June 29)

Tape springs are compliant mechanisms used as alternative to kinematic joints, for example, in deployable space structures. To reach a detailed understanding of their highly nonlinear behaviour, involving ... [more ▼]

Tape springs are compliant mechanisms used as alternative to kinematic joints, for example, in deployable space structures. To reach a detailed understanding of their highly nonlinear behaviour, involving buckling, the formation of folds, nonlinear vibrations and hysteresis, an experimental set-up is designed. Dynamic and quasi-static tests are performed, as well as small amplitude vibration tests and large amplitude deployments in order to collect data in a broad variety of cases. The acquisition equipment consists of a 3D motion analysis system which triangulates the position of active markers and a force plate. The reproducibility of the acquisitions is assessed and the parameters affecting the measurements are identified. In the end, a finite element model is developed and correlated with the experimental results. [less ▲]

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See detailRelevance of early stretching in overhead athletes
Schwartz, Cédric ULg; Tubez, François ULg; Croisier, Jean-Louis ULg et al

Conference (2017, June 16)

Overhead athletes often develop, over time, a tightness of the posterior structures of the shoulder, which may be associated with injuries. Ten symptomatic (with pain) and ten asymptomatic players with a ... [more ▼]

Overhead athletes often develop, over time, a tightness of the posterior structures of the shoulder, which may be associated with injuries. Ten symptomatic (with pain) and ten asymptomatic players with a tight shoulder were compared and the effect of a self-applied stretching program was evaluated. Before and after the stretching program, pain and stiffness of the shoulder were evaluated. Our results demonstrate that risk factors for shoulder pain such as glenohumeral internal rotation deficit and total range of motion deficit may only be limited in symptomatic athletes. The mobility of the shoulder was significantly improved after the stretching program for both groups. Pain was reduced when present. Because of the limited differences between the symptomatic and asymptomatic athletes, clinicians may find it advantageous to initiate early prevention or rehabilitation programs. [less ▲]

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See detailInfluence of the laboratory context and the size of the markers set on the tennis serve evaluation
Tubez, François ULg; Forthomme, Bénédicte ULg; Croisier, Jean-Louis ULg et al

Conference (2017, June 15)

The purpose of this study was to identify the influence on the tennis serve evaluation of 1/ the test environment and 2/ the number of the markers placed of the player. Two different studies were ... [more ▼]

The purpose of this study was to identify the influence on the tennis serve evaluation of 1/ the test environment and 2/ the number of the markers placed of the player. Two different studies were performed. The first compared a 4 vs. 28 marker set in a laboratory the same day. The second compared a 4 markers test in a laboratory with a 4 markers test on an official tennis court one week apart. We observed similar results between the different tests of both studies. [less ▲]

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See detailAmbulatory System for Gait Analysis
Boutaayamou, Mohamed ULg; Bruls, Olivier ULg; Croisier, Jean-Louis ULg et al

Conference (2017, April 29)

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

We describe the principle and use of a wireless, 3-axis accelerometer-based ambulatory system that records acceleration signals and automatically analyses them to characterize normal and pathological gait. The associated algorithm is versatile enough to detect, on a stride-by-stride basis, refined gait parameters that quantify subtle gait disturbances in, e.g., in Parkinson’s disease in a rater-independent way. The experimental results show the potential of the developed accelerometer-based technique to be used in neurology (e.g., characterization of Parkinsonian gait: slowness, shuffling, short steps, freezing of gait, asymmetries in gait), rehabilitation, geriatrics (ex. monitoring activity parameters in the elderly), orthopedics and sport. [less ▲]

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See detailMotion analysis: a prevention tool
Schwartz, Cédric ULg; CROISIER, Jean-Louis ULg; Forthomme, Bénédicte ULg et al

Conference (2017, April 28)

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See detailFactors to be considered to perform a kinematic evaluation of the tennis serve
Tubez, François ULg; Forthomme, Bénédicte ULg; Croisier, Jean-Louis ULg et al

in Journal of Medecine and Science in Tennis (2017), 22

With the 2D video cameras and later the appearance of 3D measurement methods, the tennis serve has been increasingly studied. In order to improve the biomechanical evaluation of the tennis serve. Our goal ... [more ▼]

With the 2D video cameras and later the appearance of 3D measurement methods, the tennis serve has been increasingly studied. In order to improve the biomechanical evaluation of the tennis serve. Our goal is to provide a comprehensive view of the major factors of an evaluation protocol. [less ▲]

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See detailAlgorithm for Temporal Gait Analysis Using Wireless Foot-Mounted Accelerometers
Boutaayamou, Mohamed ULg; Denoël, Vincent ULg; Bruls, Olivier ULg et al

Book published by Springer (2017)

We present a new signal processing algorithm that extracts five gait events: heel strike, toe strike, heel-off, toe-off, and heel clearance from only two accelerometers attached on the heels of the ... [more ▼]

We present a new signal processing algorithm that extracts five gait events: heel strike, toe strike, heel-off, toe-off, and heel clearance from only two accelerometers attached on the heels of the subjects usual shoes. This algorithm first uses a continuous wavelet-based segmentation that parses the signal of consecutive strides into motionless periods defining relevant local acceleration signals. Then, the algorithm uses versatile techniques to accurately extract the five gait events from these local acceleration signals. We validated, on a stride-by-stride basis, the extraction of these gait events by comparing the results with reference data provided by a kinematic 3D analysis system and a video camera. The accuracy and precision achieved by the extraction algorithm for healthy subjects, the reduced number of accelerometer units required, and the validation results obtained, encourage us to further study this system in pathological conditions. [less ▲]

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See detailCaractéristiques et évolution de la force après rééducation de la rupture de coiffe des rotateurs
Forthomme, Bénédicte ULg; Schwartz, Cédric ULg; MAHIEU, Xavier ULg et al

in Abstract Book des XVIIIèmes RENCONTRES ISOCINETIQUES MEDIMEX / ROTSCHILD (2016, November)

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See detailGait pattern of healthy old people for fast walking condition
GILLAIN, Sophie ULg; Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg et al

in Gerontechnology (2016, September)

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See detailGait pattern of healthy old people for dual task walking condition
GILLAIN, Sophie ULg; Boutaayamou, Mohamed ULg; Schwartz, Cédric ULg et al

in Gerontechnology (2016, September)

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See detailReproducibility of a tennis serve protocol
Tubez, François ULg; FORTHOMME, Bénédicte ULg; Croisier, Jean-Louis ULg et al

Conference (2016, July 08)

INTRODUCTION Serve in modern tennis game is a real offensive weapon for players. In kinematic analysis, it is the most studied stroke of this game because it is the only stroke played in a closed skill ... [more ▼]

INTRODUCTION Serve in modern tennis game is a real offensive weapon for players. In kinematic analysis, it is the most studied stroke of this game because it is the only stroke played in a closed skill. Players have a maximum of control on this stroke. It is unclear whether 3D kinematic tests are reproducible for the same player under identical conditions and if a familiarization session is necessary. In practice, with professional players, who have little time available to perform tests, familiarization sessions are difficult. The aim of our study is to measure the reproducibility of a 3D serve protocol test. METHODS Nine tennis players (righties, regional level, 20 ± 2 years) were asked to hit first flat serves in a 1 m² area placed on the "T" zone of deuce diagonal of the tennis court. Two identical tests are performed one week apart. For each test, we selected the three best serves of the 25 trials (with the highest speed and the highest accuracy). Kinetics measurements were performed using a 3D analysis system (Codamotion), a force platform (Kistler) and a radar gun. 28 markers were placed on the players’ bodies to measure kinematics of the movements: ankles, knees, hips, trunk, shoulder, elbow and wrist dominant side. We measured ball speed, leg drive, linear velocity of the racket and joints, joints range of motion and maximum angular velocities at different positions (armed, maximum external rotation and impact) (1). RESULTS All analyzed parameters (linear speeds of racket and joints, leg drive force, joint angles and angular velocities) are reproducible with exception of a small part of them. Our study shows that 5,7% (7 of 122 measurements) joint position parameters and 8,3% (4 of 48 measures) angular velocity parameters are not reproducible from a session to another. DISCUSSION Various errors sources encountered in 3D analysis can justify the presence of non-reproducible parameters (2-3). However, after this work, we can state that the established protocol provides reproducible results when analyzing the tennis serve. [less ▲]

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See detailA Comparison of 3D Methods for Identifying the Stance Phase in Treadmill Running for Both Rearfoot and Forefoot Runners
Deflandre, Dorian ULg; Schwartz, Cédric ULg; Weertz et al

in Journal of sports Science (2016), 4

We compared six 3D methods, OptoGait, and Myotest Run for the determination of contact time for runners with different foot strike patterns. Twenty male participants were divided into two groups: the heel ... [more ▼]

We compared six 3D methods, OptoGait, and Myotest Run for the determination of contact time for runners with different foot strike patterns. Twenty male participants were divided into two groups: the heel group, who attack the ground with the heel (n = 12), and the toe group, who attack the ground with the middle/front of the foot (n = 8). They performed trials at speeds of 8 km/h then 16 km/h. To detect foot strike, the use of peak velocity of 3D markers located on the heel, the fifth metatarsal, and the great toe provided the best results for both groups. To detect the toe off, the minimum vertical position of a 3D marker placed in line with the great toe gave the most satisfactory results for both groups. In this way, the values of contact time measured with the 3D methods are consistent. Values measured with OptoGait appear consistent too, while those of the Myotest Run underestimate the contact time for both speeds. 3D analysis provides interesting opportunities for calculation of contact time for both rearfoot and forefoot runners, using specific peak velocities to determine foot strike and marker displacement to determine toe off. [less ▲]

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