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International audience; Although pedaling is constrained by the circular trajectory of the pedals, it is not a simple movement. This review attempts to provide an overview of the pedaling technique using an electromyographic (EMG) approach. Literature concerning the electromyographic analysis of pedaling is reviewed in an effort to make a synthesis of the available information, and to point out its relevance for researchers, clinicians and/or cycling/triathlon trainers. The first part of the review depicts methodological aspects of the EMG signal recording and processing. We show how the pattern of muscle activation during pedaling can be analyzed in terms of muscle activity level and muscle activation timing. Muscle activity level is generally quantified with root mean square or integrated EMG values. Muscle activation timing is studied by defining EMG signal onset and offset times that identify the duration of EMG bursts and, more recently, by the determination of a lag time maximizing the cross-correlation coefficient. In the second part of the review, we describe whether the patterns of the lower limb muscles activity are influenced by numerous factors affecting pedaling such as power output, pedaling rate, body position, shoe–pedal interface, training status and fatigue. Some research perspectives linked to pedaling performance are discussed throughout the manuscript and in the conclusion.

L’objectif de cette etude etait d’analyser l’evolution des interactions tuteur-stagiaire en situation d’entretien post-lecon en plc2-EPS. Elle a ete conduite dans le cadre theorique et methodologique du « cours d’action » (Theureau, 2004). Deux dyades tuteur-stagiaire ont participe a cette etude et deux entretiens (un au debut, l’autre au milieu de l’annee scolaire) ont ete etudies pour chaque dyade. L’analyse de la dynamique des engagements des acteurs a montre que les interactions evoluaient au cours de l’entretien devenant plus cordiales et plus propices au partage et a la recherche d’autonomie. Les resultats sont discutes en relation avec la trajectoire d’apprentissage professionnel des stagiaires et une hypothese d’un isomorphisme entre l’evolution a l’echelle de l’entretien et celle qui se manifeste a l’echelle de l’annee scolaire est proposee.

International audience; Purpose: Alterations of the mechanical patterns during an exhaustive pedaling exercise have been previously shown. We designed the present study to test the hypothesis that these alterations in the biomechanics of pedaling, which occur during exhaustive exercise, are linked to changes in the activity patterns of lower limb muscles. Methods: Ten well-trained cyclists were tested during a limited time to exhaustion, performing 80% of maximal power tolerated. Pedal force components were measured continuously using instrumented pedals and were synchronized with surface EMG signals measured in 10 lower limb muscles. Results: The results confirmed most of the alterations of the mechanical patterns previously described in the literature. The magnitude of the root mean squared of the EMG during the complete cycle (RMS cycle) for tibialis anterior and gastrocnemius medialis decreased significantly (P G 0.05) from 85% and 75% of T lim , respectively. A higher RMS cycle was obtained for gluteus maximus (P G 0.01) and biceps femoris (P G 0.05) from 75% of T lim. The k values that resulted from the cross-correlation technique indicated that the activities of six muscles (gastrocnemius medialis, gastrocnemius lateralis, tibialis anterior, vastus lateralis, vastus medialis, and rectus femoris) were shifted forward in the cycle at the end of the exercise. Conclusions: The large increases in activity for gluteus maximus and biceps femoris, which are in accordance with the increase in force production during the propulsive phase, could be considered as instinctive coordination strategies that compensate for potential fatigue and loss of force of the knee extensors (i.e., vastus lateralis and vastus medialis) by a higher moment of the hip extensors.

International audience; The purpose of this study was to investigate the influence of upper-limb inertia on the force-velocity relationship and maximal power during concentric bench press exercise. Reference peak force values (Fpeakp) measured with a force plate positioned below the bench were compared to those measured simultaneously with a kinematic device fixed on the barbell by taking (Fpeakt) or not taking (Fpeakb) upper-limb inertia into account. Thirteen men (27.8 6 4.1 years, 184.6 6 5.5 cm, 99.5 6 18.6 kg) performed all-out concentric bench press exercise against 8 loads ranging between 7 and 74 kg. The results showed that for each load, Fpeakb was significantly less than Fpeakp (P , 0.0001), whereas no significant difference was found between Fpeakp and Fpeakt. The values of maximal force (F0), maximal velocity (V0), optimal velocity (Vopt), and maximal power (Pmax), extrapolated from the force-and power-velocity relationships determined with the kinematic device, were significantly underestimated when upper-limb inertia was ignored. The results underline the importance of taking account of the total inertia of the moving system to ensure precise evaluation of upper-limb muscular characteristics in all-out concentric bench press exercise with a kinematic device. A major application of this study would be to develop precise upper-limb muscular characteristic evaluation in laboratory and field conditions by using a simple and cheap kinematic device.

Background . No study has reported the possibility of establishing torque–velocity and power–velocity relationships for both flexor and extensor trunk muscles. The present study therefore sought to assess these relationships during isokinetic exercise. Methods . Nine healthy male subjects performed series of isokinetic trunk flexions and extensions at six different velocities ranging from 45° s −1 to 120° s −1 . Trunk flexor and extensor muscles were, respectively, assessed on two separate days. All experiments used a Biodex dynamometer. Findings . Torque–velocity relationships were significantly well described by a linear relationship for both trunk flexor ( P r = 0.92–0.99) and extensor muscles ( P r = 0.82–0.97) in all subjects. Power–velocity relationships exhibited a parabolic shape for all subjects ( P r = 0.96–0.99) for both muscle groups. Interpretation . Results showed that trunk muscle torque– and power–velocity relationships can be assessed during isokinetic exercise. The findings were in agreement with previous studies of lower and upper limbs. This kind of measurement can therefore be applied in assessing low-back pain patients during rehabilitation.

Cette étude visait à analyser les processus d'ajustements mutuels et de co-construction de connaissances entre les élèves dans des tâches collectives d'apprentissage en EPS, au cours d'un cycle de volley-ball. Elle a été conduite dans le cadre théorique du " cours d'action ", en référence à l'objet théorique de l'articulation collective des cours d'expérience. Les comportements de trois collégiens ont été enregistrés lors de séances de volley-ball, suivies d'entretiens d'autoconfrontation avec chacun des élèves. L'analyse de l'articulation des cours d'expérience a permis de décrire différentes formes d'ajustement des activités des élèves, et de construction et partage (ou non) de connaissances au sein du groupe. Trois formes typiques d'activité collective ont été caractérisées et qualifiées : (a) évolution d'un non-partage à un partage partiel de connaissances entre les élèves, (b) de tutelle spontanée entre élèves, et (c) de construction de connaissances " conflictuelles ". Ces résultats questionnent les notions de " communauté de pratique " et de " trajectoire de participation " dans les apprentissages en EPS. De plus, ils montrent comment les élèves s'adaptent collectivement aux tâches scolaires sans nécessairement partager les connaissances a priori requises dans la réalisation de ces tâches. Enfin, ils révèlent des formes singulières de " compagnonnage cognitif " entre les élèves

International audience; Assessment of intra-session repeatability of muscle activation pattern is of considerable relevance for research settings, especially when used to determine changes over time. However, the repeatability of lower limb muscles activation pattern during pedaling is not fully established. Thus, we tested the intra-session repeatability of the activation pattern of 10 lower limb muscles during a sub-maximal cycling exercise. Eleven triathletes participated to this study. The experimental session consisted in a reference sub-maximal cycling exercise (i.e. 150 W) performed before and after a 53-min simulated training session (mean power output = 200 ± 12 W). Repeatability of EMG patterns was assessed in terms of muscle activity level (i.e. RMS of the mean pedaling cycle and burst) and muscle activation timing (i.e. onset and offset of the EMG burst) for the 10 following lower limb muscles: gluteus maximus (GMax), semimembranosus (SM), Biceps femoris (BF), vastus medialis (VM), rectus femoris (RF), vastus lateralis (VL), gastrocnemius medianus (GM) and lateralis (GL), soleus (SOL) and tibialis anterior (TA). No significant differences concerning the muscle activation level were found between test and retest for all the muscles investigated. Only VM, SOL and TA showed significant differences in muscle activation timing parameters. Whereas ICC and SEM values confirmed this weak repeatability, cross-correlation coefficients suggest a good repeatability of the activation timing parameters for all the studied muscles. Overall, the main finding of this work is the good repeatability of the EMG pattern during pedaling both in term of muscle activity level and muscle activation timing.

Passive muscle stretching can be used in vivo to assess the viscoelastic properties of the entire musculo-articular complex, but does not allow the specific determination of the muscle or tendon viscoelasticity. In this respect, the local muscle hardness (LMH) of the gastrocnemius medialis (GM) belly was measured during a passive ankle stretching of 10 subjects using transient elastography. A Biodex isokinetic dynamometer was used to stretch ankle plantar flexors, to measure ankle angle, and the passive torque developed by the ankle joint in resistance to the stretch. Results show that the LMH increased during the stretching protocol, with an averaged ratio between maximal LMH and minimal LMH of 2.6270.46. Furthermore, LMH–passive torque relationships were nicely fitted using a linear model with mean correlation coefficients (R 2 ) of 0.82870.099. A good reproducibility was found for the maximal passive torque (ICC ¼ 0.976, SEM ¼ 2.9 N m, CV ¼ 5.5%) and the y-intercept of the LMH–passive torque relationship (ICC ¼ 0.893, SEM ¼ 105 Pa, CV ¼ 7.8%). However, the reproducibility was low for the slope of this relationship (ICC ¼ 0.631, SEM ¼ 10.35 m � 2 ,C V¼ 60.4%). The y-intercept of the LMH–passive torque relationship was not significantly changed after 10 min of static stretching. This result confirms the finding of a previous study indicating that changes in passive torque following static stretching could be explained by an acute increase in muscle length without any changes in musculo-articular intrinsic mechanical properties. r 2008 Elsevier Ltd. All rights reserved.

International audience; The aim of this study was to implement a rheological model of the mechanical behaviour of the passive musculo-articular complex (MAC). Nine healthy subjects performed five passive stretching cycles and five passive cycles preset at different velocities (0.035, 0.52, 1.05, 1.57 et 2.09 rad/s). All the protocol was realized using an isokinetic dynamometer, which enabled to measure the articular angle and the torque produced by the MAC in resistance to the stretch. The model was composed of non linear elasticity, linear viscoelasticity and friction. It was implemented using Simulink software, and the nine parameters were determined, for each subject, by minimizing the difference between the model and the experience using the non linear least square method. Results show a good agreement between the model and experimental data, which validate the choice of our model.; L'objectif de cette étude est de mettre en place un modèle rhéologique du comportement mécanique du complexe musculo-articulaire (CMA) placé en conditions passives. Après cinq cycles de pré conditionnement, neuf sujets asymptomatiques ont réalisé 5 étirements passifs à 5 vitesses différentes (0.035, 0.52, 1.05, 1.57 et 2.09 rad/s) sur un dynamomètre permettant de mesurer l'angle et le couple développés par le CMA en résistance à l'étirement. Un modèle associant élasticités non linéaires, viscoélasticité linéaire et frottement a été mis en place sous Simulink, et les neuf paramètres constitutifs de ce modèle ont été déterminés, pour chaque sujet, en minimisant l'erreur par rapport aux données expérimentales par la méthode des moindres carrés non linéaire. Les résultats mettent en évidence un bon accord modèle/expérience, ce qui valide le choix du modèle utilisé.

The aim of this study was to examine the myoelectric manifestations of neuromuscular fatigue induced by a sustained bout of hiking with regard to training status, laterality and muscle. Nineteen subjects, separated into three different groups according to their training status in hiking, volunteered to take part in this study. Subjects performed a sustained hiking test until exhaustion at 50 % of the maximal hiking torque on a specially developed hiking ergometer. The electrical activity of two bilateral (left and right sides) muscular chains involved in hiking including the rectus abdominis (RA), rectus femoris (RF), vastus lateralis (VL), and tibialis anterior (TA) muscles was explored using surface electromyography. Results indicated a higher endurance time (Tlim) for the highly trained group in hiking (45 %, p < 0.05). The mean electrical activity of the muscles studied reached a medium level at the end of the sustained hiking period (51 % of maximal values, p < 0.001), regardless of the training status. However, the increase in activation level was delayed in hikers (50 % Tlim) compared to non-hikers (25 % Tlim), especially for rectus abdominis and rectus femoris muscles. Furthermore, activation patterns of synergistic muscles differed among the groups so that electrical activity of knee extensors was higher than that of trunk flexors of hikers at the end of hiking task (e.g., left RA: 32 % vs. left VL: 54 % of maximal values, p < 0.001). Shifts in mean power frequency were more pronounced in rectus abdominis muscles (- 24 %, p < 0.001) than in rectus femoris (- 7 %, p < 0.001) and vastus lateralis (unchanged), regardless of the group. Hikers exhibited a lower and more delayed spectral compression (left side: - 1.3 %, right side: - 9.8 %) compared to non-hikers (left and right sides: - 15.1 %). These findings suggest that hikers prolonged endurance time by adjusting neural distribution of activity among synergists, thereby minimizing the contribution of the most fatigable muscles, such as the trunk flexors.

The aim of this study was to compare the power provided by a recent ergometer with the power developed by the rower determined using mechanical sensors set on the same apparatus. Six rowers and six non-rowers performed a power graded test and an all-out start on an instrumented ergometer (Concept2 system, model D, Morrisville, VT, USA). Power values displayed by the ergometer were recorded with a specific software. A strain gauge placed near the handle and a position sensor installed on the chain allowed the calculation of the power developed by the rower. Power values provided by the ergometer were strongly correlated to those determined with a direct measurement and calculation of power. However, power values given by the Concept2 system were lower (- 17.4 to - 72.4 W) than those calculated using mechanical sensors. This difference in power measurements was lower at a steady pace and for rowers. The Concept2 system underestimates the power produced by the rower by approximately 25 W. This difference in power seems to be independent of the level of power developed but increases with variations in intensity and pace. The deletion of the first strokes following changes in power production allows to limit this phenomenon. According to the use of the power parameter in the experimental design, it could be appropriate to correct values provided by the Concept2 ergometer.

Previous research has not addressed gender differences in coping strategies among patients with mild to moderate chronic obstructive pulmonary disease (COPD) who are enrolled in inpatient and multidisciplinary rehabilitation programs.The coping strategies of 182 consecutive patients (61 women aged 61.1 years; 121 men aged 62.7 years) with mild to moderate COPD were assessed on admission and then at discharge after 29 days of pulmonary rehabilitation, using the Coping Inventory for Stressful Situations. A one-way analysis of variance for repeated measures was used to test the differences in coping scores.During the rehabilitation program, problem-focused strategies increased (+2.54 [95% confidence interval: 1.41-3.67] with F=23.77, P.0001), emotion-focused strategies decreased (-2.75 [95% confidence interval: -4.06, -1.45], F=15.37, P.001), and avoidance strategies were differently (t=2.97, P.05) influenced in women (+2.43 [95% confidence interval: .66-4.19]) compared with men (-1.30 [95% confidence interval: -2.82-.22]). The prevalence of COPD in women is increasing, and rehabilitation professionals need a greater awareness of how women cope differently than men with this disease.

A research program combining the analysis of situated activity and the development of training tools: an example from elite sport This article presents an original program that combines research and This article presents an original program that combines research and training development. Between 1997 and 2002, several studies of the activity of expert table tennis players during matches were carried out within the framework of course-of-action theory (Theureau, 1992, 2004). These studies had been formally agreed on by coaches, athletes and researchers and responded to both sports needs and scientific interests. Matches were videotaped during international meetings and followed by self-confrontation interviews during which the players described and commented on their activity as they viewed the tapes. A grounded theory of players' activity resulted from the data collected and the ensuing theoretical issues that were raised. This theory focuses on the three modes of players' involvement identified in the studies: exploration, execution and deception. The findings on table tennis players' activity led to questions about some of the usual practices of coaches and pointed to a new direction for training proposals., Cet article présente un programme original articulant une composante de recherche et une composante de conception de l'entraînement. Au cours de la période 1997-2002, plusieurs études visant à analyser l'activité des pongistes experts en match ont été conduites en référence à la théorie du cours d'action (Theureau, 1992, 2004). Ces études ont été menées dans un cadre contractuel entre les chercheurs, entraîneurs et athlètes. Des données d'enregistrement audio-visuel ont été recueillies au cours de matchs et complétées par des verbalisations provoquées. Les résultats ont donné lieu à la construction d'un modèle de l'activité des pongistes experts en match, élaboré à partir d'allers et retours entre des questionnements théoriques et les résultats des différentes études. Ce modèle s'articule autour de trois modes d'engagement caractéristiques des pongistes au cours des matchs identifiés au cours des études : l'exploration, l'exécution et la dissimulation. Il a questionné certaines pratiques usuelles des entraîneurs, et a donné lieu à la conception de nouvelles propositions d'entraînement.

This work aims at reassessing classical conceptions of personality traits and states as well as variability related to global self-esteem and physical self, from an idiographic and dynamic approach. This research emphasizes the iterative functioning for adults which corresponds to a simple exponential smoothing model thought as a dynamical adjustment. Moreover, time series are characterized by a fractal process (pink noise) which suggests that the self can be conceived as a complex dynamical system. These conclusions led us reinvestigating the hierarchical structure of global self-esteem and physical self, as well as its functioning using time series analysis. Surpassing recurrent limitations of classical approaches, the application of Dynamical Systems Theory allows providing new insights concerning the mechanisms by which dimensions are interconnected and especially the direction of the causal flow in the model. In conclusion, we provide a heuristic for theory construction, methodology perspectives and clinical applications.; A partir d'une approche idiographique et dynamique, nous avons revisité les conceptions classiques de trait, d'état de personnalité et de variabilité de l'estime globale de soi et du soi physique. Ce travail met en exergue, chez l'adulte, un fonctionnement itératif de moyenne mobile avec différenciation, conçu comme un ajustement dynamique. La mise en évidence de la nature fractale des séries temporelles suggère que le soi puisse être considéré comme un système dynamique complexe. Ces premières conclusions nous ont amené à réévaluer la structure hiérarchique de l'estime globale de soi et du soi physique, non plus dans une perspective nomothétique, mais à partir de séries temporelles individuelles. Dépassant certaines limites des approches classiques, l'utilisation de la théorie des systèmes dynamiques permet d'apporter des réponses quant aux processus d'influence qui gouvernent le fonctionnement de ce système : l'effet réciproque. Ce travail offre de nouvelles perspectives théoriques, méthodologiques et cliniques dans le champ de la psychologie sociale.

International audience; This paper both presents a framework for analyzing situated emotions and describes the evolution of two teachers' emotions during their first classroom experiences. Based on Peirce's three categories of experience (1931-1935), we categorized teachers' emotions into affective states, sentiments and emotions-types. The principal results show (a) the emotional flow during ordinary teaching situations, (b) the emergence of contradictory emotions related to phenomena of emotional hysteresis between the affective states and sentiments, (c) the typical character of their emotions related to dependence on the lesson plan and the need to maintain student activity, and (d) the importance of typicalization of emotions in learning to teach.

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The purpose of this study was to determine the importance of leg strength and stiffness relative to i) 100 m sprint performance, ii) mean speed on the three phases of the 100 m race (30-60-100 m) and iii) the speed differences between these phases.Nineteen regional to national level male sprinters competed in a 100 m race. Video analysis was used to determine mean velocity parameters. Two subgroups were created since some of the runners decreased their velocity during the third phase (G1), whereas others maintained or accelerated it (G2). Leg strength (concentric half-squats - counter movement jump) and stiffness (hopping) were determined. Simple (r) and multiple regressions (R) were used.The mean performance over 100 m was 11.43 sec (10.72-12.87 sec). The concentric half-squats were related to 100 m (r=0.74, p0.001) and to the mean speed of each phase (R=0.75, p0.01). The counter movement jump was related to 100 m (r=0.57, p0.05) and was the predictor of the first phase (r=0.66, p0.01). The hopping test was the predictor of the two last phases (R=0.66, p0.05). Athletes who had the greatest leg stiffness (G1) produced the highest acceleration between the first and the second phases, and presented a deceleration between the second and the third ones.The concentric half-squats test was the best predictor in the 100 m sprint. Leg stiffness plays a major role in the second phase.

International audience; Après la présentation d'une démarche originale de description de l'expérience humaine, la recherche analyse les dilemmes vécus par deux enseignants débutants et la manière dont ils les résolvent. Elle discute ensuite de l'intérêt d'une telle étude de cas dans les plans de formation initiale. Cette étude montre que les débutants vivent plus fréquemment des dilemmes que les professeurs plus expérimentés. Ces dilemmes spécifiques aux débutants opposent différentes orientations possibles de l'action liées à plusieurs préoccupations émergeant simultanément : les unes et les autres peuvent se concrétiser séparément mais se révèlent incompatibles - pour les débutants - mutuellement dans la même action. Le dilemme (selon cette définition extensive) est vécu comme la construction d'une "réalité impossible" alors même qu'une position d'extériorité (en formation) permettrait de mettre en cause ce qui a été estimé impossible.

Objectives This review aims to define the concept of neuromuscular fatigue and to present the current knowledge of the central and peripheral factors at the origin of this phenomenon. This review also addresses the literature that focuses on the mechanisms responsible for the adaption to neuromuscular fatigue. Method One hundred and eighty-two articles indexed in PubMed (1954–2010) have been considered. Results Neuromuscular fatigue has central and peripheral origins. Central fatigue, preponderant during long-duration, low-intensity exercises, may involve a drop in the central command (motor, cortex, motoneurons) elicited by the activity of cerebral neurotransmitters and muscular afferent fibers. Peripheral fatigue, associated with an impairment of the mechanisms from excitation to muscle contraction, may be induced by a perturbation of the calcium ion movements, an accumulation of phosphate, and/or a decrease of the adenosine triphosphate stores. To compensate for the consequent drop in force production, the organism develops several adaptation mechanisms notably implicating motor units. Conclusion Fatigue onset is associated with an alteration of the mechanisms involved in force production. Then, the interaction between central and peripheral mechanisms leads to a series of events that ultimately contribute to the observed decrease in force production.

Characterization of interpersonal coordination modes within a basket-ball team. The aim of our study was to analyze the construction of a collective activity. We focused on interpersonal coordination process within a basket-ball team during a match. We characterized the way how basketball players took mutually into account their respective activities. In order to consider in the same time both units of analysis, the individual one and the collective one, this study referred to the framework of the course of action theory (Theureau, 2006). Results allowed us to specify the relational network between players, the various coordination modes between two players and the different forms of team coordination. These results are discussed with regard to the nature of interactions within the team, and with regard to the notion of a collective action plan : they highlighted that some collective activity construction modalities are based on local overlapping coordination. These results thus question the status of a collective plan (as a scheme shared by all the players)., Caractérisation de modes de coordination interpersonnels dans une équipe de basket-ball. Le but de notre étude était d'analyser la construction d'une activité collective. Nous nous sommes concentrés sur le processus de coordination interpersonnel dans une équipe de basket-ball pendant un match(une allumette). Nous avons caractérisé la voie comment les basketteurs ont pris mutuellement en considération leurs activités respectives. Pour considérer dans le même temps les deux unités d'analyse, le individuel et le collectif, cette étude a mentionné la structure du cours de théorie d'action (Theureau, 2006). Les résultats nous ont permis de spécifier le réseau relationnel entre des acteurs(joueurs), les modes de coordination divers entre deux acteurs(joueurs) et les formes(formulaires) différentes de coordination d'équipe. Ces résultats sont discutés en ce qui concerne la nature d'interactions dans l'équipe et en ce qui concerne la notion d'un plan d'action collectif : ils ont mis en évidence(ont surligné) ces quelques modalités de construction d'activité collectives sont basé sur la coordination de chevauchement locale. Ces résultats mettent ainsi en doute le statut d'un plan collectif (comme un plan(arrangement) partagé par tous les acteurs(joueurs)).

Cette étude porte sur un " format pédagogique " ancien et très répandu : le cours dialogué. À partir d'une étude en géographie, à l'école primaire, l'activité en classe a été analysée à deux niveaux, individuel et collectif. Les préoccupations et émotions qui orientent l'activité individuelle de l'enseignante et des élèves ont été décrites. Puis, à partir de l'enchaînement des questions, réponses et évaluations, des structures d'articulation des activités individuelles ont été identifiées. Elles ont permis de modéliser le cours dialogué et de mettre en évidence sa stabilité et sa viabilité. Nous considérons que ces caractéristiques contribuent à expliquer sa pérennité et sa vitalité.