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See detailValidated assessment of gait sub-phase durations in older adults using an accelerometer-based ambulatory system
Boutaayamou, Mohamed ULiege; GILLAIN, Sophie ULiege; Schwartz, Cédric ULiege et al

in Proceedings of the 11th International Joint Conference on Biomedical Engineering Systems and Technologies (BIOSTEC 2018) (in press)

Validated extraction of gait sub-phase durations using an ambulatory accelerometer-based system is a current unmet need to quantify subtle changes during the walking of older adults. In this paper, we ... [more ▼]

Validated extraction of gait sub-phase durations using an ambulatory accelerometer-based system is a current unmet need to quantify subtle changes during the walking of older adults. In this paper, we describe (1) a signal processing algorithm to automatically extract not only durations of stride, stance, swing, and double support phases, but also durations of sub-phases that refine the stance and swing phases from foot-worn accelerometer signals in comfortable walking of older adults, and (2) the validation of this extraction using reference data provided by a gold standard system. The results show that we achieve a high agreement between our method and the reference method in the extraction of (1) the temporal gait events involved in the estimation of the phase/sub-phase durations, namely heel strike (HS), toe strike (TS), toe-off (TO), maximum of heel clearance (MHC), and maximum of toe clearance (MTC), with an accuracy and precision that range from ‒3.6 ms to 4.0 ms, and 6.5 ms to 12.0 ms, respectively, and (2) the gait phase/sub-phase durations, namely stride, stance, swing, double support phases, and HS to TS, TO to MHC, MHC to MTC, and MTC to HS sub-phases, with an accuracy and precision that range from ‒4 ms to 5 ms, and 9 ms to 15 ms, respectively, in comfortable walking of a thirty-eight older adults ( (mean ± standard deviation) 71.0 ± 4.1 years old). This demonstrates that the developed accelerometer-based algorithm can extract validated temporal gait events and phase/sub-phase durations, in comfortable walking of older adults, with a promising degree of accuracy/precision compared to reference data, warranting further studies. [less ▲]

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See detailInfluence of a dynamic seating habit on lumbar control motor in schoolchildren
Fettweis, Tatiana ULiege; Onkelinx, Marie-Noëlle; Schwartz, Cédric ULiege et al

in Journal of Back and Musculoskeletal Rehabilitation (in press)

BACKGROUND: Adequate motor control is considered important for spinal stability and the prevention of low back pain in adulthood and in childhood. OBJECTIVE: Given that the sitting position can affect ... [more ▼]

BACKGROUND: Adequate motor control is considered important for spinal stability and the prevention of low back pain in adulthood and in childhood. OBJECTIVE: Given that the sitting position can affect proprioception, this study aimed to evaluate the influence of using at school a triangular and dynamic cushion on schoolchildren’s trunk motor control. METHODS: Thirty 8-year-old schoolchildren were randomized into a control group (n=15) and a “cushion group” (n=15), in which the children used the cushion for one year and a half. At the end of this period, a 3D-analysis was used to assess lumbar spine proprioception by means of a trunk repositioning task performed blindfolded in a seated position in two conditions (on a stable and on an unstable surface). RESULTS: The schoolchildren in the cushion group performed better at the trunk repositioning task (p=0.02) and hold their lumbar lordosis (p=0.03) better than the control children, in both conditions (stable and unstable). CONCLUSIONS: This preliminary study suggests that daily use of a triangular dynamic cushion has a beneficial impact on children’s lumbar proprioception. Further studies are needed to confirm these results and investigate the effectiveness of its use to prevent low back pain in adulthood. [less ▲]

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See detailWhich tool for a tennis serve evaluation? A review
Tubez, François ULiege; Schwartz, Cédric ULiege; Paulus, Julien ULiege et al

in International Journal of Performance Analysis in Sport (2018)

For coaches, the most common and easiest way to analyse the tennis serve is to refer to their own vision. However, human vision is insufficient to observe high-speed motion with great precision. With the ... [more ▼]

For coaches, the most common and easiest way to analyse the tennis serve is to refer to their own vision. However, human vision is insufficient to observe high-speed motion with great precision. With the improvement of technology, it is now possible to study the gesture from a quantitative point of view. The quantitative evaluation of the tennis serve focuses on the kinematics and kinetics of the player but also on the stroke result, which includes the ball speed and the ball trajectory. This review aims to highlight the current tools available for players, coaches, medical staffs and biomechanical researchers, to evaluate the tennis serve. This overview will provide information to the player’s entourage in order to choose the right tools depending on their specific purposes. All of these tools can be applied in performance improvement and injury prevention. [less ▲]

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See detailEvaluation of ground reaction forces based on kinematic data
Van Hulle, Romain ULiege; Schwartz, Cédric ULiege; Bruls, Olivier ULiege

Poster (2017, December 01)

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See detailNormalizing shoulder EMG: an optimal set of maximum isometric voluntary contraction tests considering reproducibility
Schwartz, Cédric ULiege; Tubez, François ULiege; WANG, François-Charles ULiege et al

in Journal of Electromyography and Kinesiology (2017), 37

Normalization of the electromyography (EMG) signal is often performed relatively to maximal voluntary activations (MVA) obtained during maximum isometric voluntary contraction (MVIC). The first aim was to ... [more ▼]

Normalization of the electromyography (EMG) signal is often performed relatively to maximal voluntary activations (MVA) obtained during maximum isometric voluntary contraction (MVIC). The first aim was to provide an inter-session reproducible protocol to normalize the signal of eight shoulder muscles. The protocol should also lead to a level of activation >90% of MVA for >90% of the volunteers. The second aim was to evaluate the influence of the method used to extract the MVA from the EMG envelope on the normalized EMG signal. Thirteen volunteers performed 12 MVICs twice (one-week interval). Several time constants (100 ms to 2 s) were compared when extracting the MVA from the EMG envelope. The EMG activity was also acquired during an arm elevation. Our results show that a combination of nine MVIC tests was required to meet our requirements including reproducibility. Both the number of MVIC tests and the size of the time constant influence the normalized EMG signal during the dynamic activity (variations up to 15%). A time constant of 1 s was a good compromise to extract the MVA. These findings are valuable to improve the reproducibility of EMG signal normalization. [less ▲]

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See detailA gait cycle partitioning method using a foot-worn accelerometer system
Boutaayamou, Mohamed ULiege; Bruls, Olivier ULiege; Denoël, Vincent ULiege et al

Conference (2017, November 30)

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See detailA gait cycle partitioning method using a foot-worn accelerometer system
Boutaayamou, Mohamed ULiege; Bruls, Olivier ULiege; Denoël, Vincent ULiege et al

Conference (2017, November 30)

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See detailLa β-alanine dans des épreuves isocinétiques et de sauts répétés, (in)utile?
Paulus, Julien ULiege; Schwartz, Cédric ULiege; Paquot, Nicolas ULiege et al

Poster (2017, October 30)

Introduction La β-alanine (β-A), acide aminé précurseur de la carnosine, a fait l'objet d'un nombre important d'études sans néanmoins parvenir à un consensus quant à son influence sur la performance [1-6 ... [more ▼]

Introduction La β-alanine (β-A), acide aminé précurseur de la carnosine, a fait l'objet d'un nombre important d'études sans néanmoins parvenir à un consensus quant à son influence sur la performance [1-6] et/ou son mécanisme d'action [7]. Notre étude a pour but d'affiner la connaissance de son impact sur des performances maximales lors d'épreuves isocinétiques et de sauts prolongées: les personnes ayant une faible résistance à la fatigue neuromusculaire bénéficieraient-elles davantage des effets de la β-A? Méthodes Neuf hommes (24,5 ± 1,2 ans, 182,1 ± 6,6 cm, 80,2 ± 9,9 kg), ont réalisé deux épreuves d'exploration de la fatigue neuromusculaire avec 48h à 72h de repos entre chaque: un test analytique mono-articulaire, gold standard de l'évaluation musculaire, et une épreuve poly-articulaire dite "fonctionnelle". Ces deux épreuves, complémentaires de par les informations qu'elles permettent d'obtenir, sont respectivement un test isocinétique de résistance à la fatigue (30 extensions/flexions maximales de genou en concentrique à 180°.s-1 sur une amplitude de 100° sur Cybex Humac CSMI) [8] et un test de countermovement jump répétés (35 sauts maximaux enclenchés toutes les 1,82 secondes). Chaque sujet a réalisé quatre fois chaque testing: avant/après 14 jours de supplémentation en β-A (5g/j.) et avant/après 14 jours de prise d'un placebo (lactose) sous forme d'un crossover randomisé en double aveugle avec un wash-out de 14 jours. Résultats Aucun effet global de la supplémentation en β-A n'a été observé, que ce soit pour l'épreuve isocinétique (entre autres, somme du travail total des extenseurs: ES Cohen = 0,06 [CI95%: -0,57/0,68]; Magnitude-Based Inference (MBI) Hopkins: P (positif) 31% / T (trivial) 51% / N (négatif) 18%) ou de sauts répétés (entre autres, somme des hauteurs des 35 sauts: ES Cohen = -0,09 [CI95%: -0,47/0,28]; MBI: P 5% / T 68% / N 26%). Une corrélation négative (inversement proportionnelle), forte et statistiquement significative a néanmoins été observée entre l'impact de la β-A sur la performance et la capacité de résistance à la fatigue neuromusculaire pour l'épreuve isocinétique (entre autres, pente de la régression linéaire du travail total & différence entre somme du travail total des extenseurs avec β-A et placebo: rPearson = - 0,85 [CI95%: -0,97/-0,44] avec une p-value de 0,002). Pour l'épreuve de sauts répétés, les résultats ne sont pas significatifs (rPearson = - 0,31 [CI95%: -0,81/0,44] avec une p-value de 0,409). [less ▲]

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

in European Journal of Sport Science (2017), 17(9), 1143-1152

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 detailExperimental and numerical investigation of the nonlinear dynamics of compliant mechanisms for deployable structures
Dewalque, Florence ULiege; Schwartz, Cédric ULiege; Denoël, Vincent ULiege et al

in Mechanical Systems & Signal Processing (2017), 101

This paper studies the dynamics of tape springs which are characterised by a highly geometrical nonlinear behaviour including buckling, the formation of folds and hysteresis. An experimental set-up is ... [more ▼]

This paper studies the dynamics of tape springs which are characterised by a highly geometrical nonlinear behaviour including buckling, the formation of folds and hysteresis. An experimental set-up is designed to capture these complex nonlinear phenomena. The experimental data are acquired by the means of a 3D motion analysis system combined with a synchronised force plate. Deployment tests show that the motion can be divided into three phases characterised by different types of folds, frequencies of oscillation and damping behaviours. Furthermore, the reproducibility quality of the dynamic and quasi-static results is validated by performing a large number of tests. In parallel, a nonlinear finite element model is developed. The required model parameters are identified based on simple experimental tests such as static deformed configurations and small amplitude vibration tests. In the end, the model proves to be well correlated with the experimental results in opposite sense bending, while in equal sense, both the experimental set-up and the numerical model are particularly sensitive to the initial conditions. [less ▲]

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See detailA Novel Accelerometer-Based Method for Stride Length Estimation
Boutaayamou, Mohamed ULiege; Schwartz, Cédric ULiege; Denoël, Vincent ULiege 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 detailMaximal voluntary isometric contraction tests for normalizing surface EMG of scapular stabilizers muscles
Schwartz, Cédric ULiege; Tubez, François ULiege; Soulier, Maxime et al

Conference (2017, July 04)

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See detailHow much should you jump? Reproducibility evaluation of a 3-dimensional fatigability countermovement jump test
Paulus, Julien ULiege; Schwartz, Cédric ULiege; Tubez, François ULiege 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 ULiege; Schwartz, Cédric ULiege; Denoël, Vincent ULiege 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 ULiege; Tubez, François ULiege; Croisier, Jean-Louis ULiege 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 ULiege; Forthomme, Bénédicte ULiege; Croisier, Jean-Louis ULiege 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 ULiege; Bruls, Olivier ULiege; Croisier, Jean-Louis ULiege 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 ULiege; CROISIER, Jean-Louis ULiege; Forthomme, Bénédicte ULiege 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 ULiege; Forthomme, Bénédicte ULiege; Croisier, Jean-Louis ULiege 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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