The influence of shoe drop on the kinematics and kinetics of children tennis players     

Alexis Herbaut  Pascale Chavet  Maxime Roux  Nils Guéguen  Christophe Gillet  Franck Barbier 《European Journal of Sport Science》2016,16(8):1121-1129

This study investigated the immediate effects of reducing the shoe drop (i.e. the difference between the heel and the forefoot height) on the kinematics and kinetics of the lower extremities of children tennis players performing a tennis-specific movement. Thirteen children tennis players performed a series of simulated open stance forehands wearing 3 pairs of shoes differing only in the drop: 0 (D0), 6 (D6) and the control condition of 12?mm (D12). Two embedded forceplates and a motion capture system were used to analyse the ground reaction forces and ankle and knee joint angles and moments of the leading lower limb. In D6 compared with D12, the peak impact force was reduced by 24% (p?=?.004) and the ankle was less dorsiflexed at foot strike (p?=?.037). In D0 compared with D12, the peak impact force was reduced by 17% (p?=?.049), the ankle was less dorsiflexed at foot strike (p?=?.045) and the knee was more flexed at foot strike (p?=?.007). In addition, 4 out of 13 participants (31%) presented a forefoot strike pattern for some of the trials in D0. No difference was observed across shoe conditions for the peak knee extensor moment (p?=?.658) or the peak ankle plantarflexor moment (p?=?.071). The results provide preliminary data supporting the hypothesis that for children tennis players, using a 6-mm lower shoe drop might reduce heel impact forces and thus limit potentially impact-related injuries.  相似文献   

Beating the bounds: The Tour de France and national identity     

Christophe Campos 《国际体育史杂志》2013,30(2):149-174

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Augmenting performance feedback does not affect 4 km cycling time-trials in the heat     

Mark Waldron  Vincent Villerius  Aron Murphy 《Journal of sports sciences》2015,33(8):786-794

We compared the effects of (1) accurate and (2) surreptitiously augmented performance feedback on power output and physiological responses to a 4000 m time-trial in the heat. Nine cyclists completed a baseline (BaseL) 4000 m time-trial in ambient temperatures of 30°C, followed by two further 4000 m time-trials at the same temperature, randomly assigning the participants to an accurate (ACC; accurate feedback of baseline) or deceived (DEC; 2% increase above baseline) feedback group. The total power output (PO) and aerobic (P_aer) and anaerobic (P_an) contributions were determined at 0.4 km stages during the time-trials, alongside measurements of rectal (T_rec) and skin (T_skin) temperatures. There were no differences (P > 0.05) in any of the variables between BaseL, ACC and DEC, despite increases (P < 0.05) in T_rec and T_skin. Typical pacing profiles were demonstrated; however, there was no interaction (P > 0.05) between feedback condition and time-trial stage. Providing surreptitiously augmented performance feedback to well-trained cyclists did not alter their performance or physiological responses to a 4000 m time-trial in a hot environment. The assumed influence of augmented performance feedback was nullified in the heat, perhaps reflecting a central down-regulation of exercise intensity in response to an increased body temperature.  相似文献   

Bridge over troubled water: using implementation science to facilitate effective services in child welfare     

Mildon R  Shlonsky A 《Child abuse & neglect》2011,35(9):753-756

To maximize benefits to children and their families, effective practices need to be used competently in child welfare settings. Since the 1990s, researchers and policy makers have focused attention on empirically supported interventions (ESIs). Much less attention has been paid to what is needed to implement these in a range of real-world settings. Without proper implementation, which includes an evaluation strategy from feasibility to fidelity to on-going work on moderators and mediators of program effects, established effective programs can be rendered ineffective in practical application. The paper will touch on progress, to date, of implementation science, its application to child welfare programs and practices, and will highlight a set of practical strategies for implementing empirically supported interventions in child welfare.  相似文献   

Students and Europe     

Christophe Campos 《Higher Education Quarterly》1972,26(3):280-309

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Mobility of university staff in Europe     

Christophe Campos 《Higher Education Quarterly》1970,25(1):28-48

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General Growth Mixture Analysis of Adolescents' Developmental Trajectories of Anxiety: The Impact of Untested Invariance Assumptions on Substantive Interpretations     

Alexandre J. S. Morin  Christophe Maïano  Benjamin Nagengast  Herbert W. Marsh  Julien Morizot  Michel Janosz 《Structural equation modeling》2013,20(4):613-648

Substantively, this study investigates potential heterogeneity in the developmental trajectories of anxiety in adolescence. Methodologically, this study demonstrates the usefulness of general growth mixture analysis (GGMA) in addressing these issues and illustrates the impact of untested invariance assumptions on substantive interpretations. This study relied on data from the Montreal Adolescent Depression Development Project (MADDP), a 4-year follow-up of more than 1,000 adolescents who completed the Beck Anxiety Inventory each year. GGMA models relying on different invariance assumptions were empirically compared. Each of these models converged on a 5-class solution, but yielded different substantive results. The model with class-varying variance–covariance matrices was retained as providing a better fit to the data. These results showed that although elevated levels of anxiety might fluctuate over time, they clearly do not represent a transient phenomenon. This model was then validated in relation to multiple predictors (mostly related to school violence) and outcomes (grade-point average, school dropout, depression, loneliness, and drug-related problems).  相似文献   

Study of Post-World War II French Aeronautical Aluminium Alloy and Coatings: Historical and Materials Science Approach     

Magali Brunet  Audrey Cochard  Christophe Deshayes  Chantal Brouca-Cabarrecq  Luc Robbiola  Jean-Marc Olivier 《文物保护研究》2020,65(2):103-117

ABSTRACT

In many countries, collections of historic aircraft, conserved in Air and Space museums or local associations, reflect the importance of a national or local history. Mostly parked outdoors, aircraft suffer from significant corrosion requiring conservation operations. During renovation, metallic parts are often replaced by association members. This can lead to a major loss of information since industrial archives dealing with materials and processes do not always survive. However, if these elements can be considered, they could be a fundamental source of information on the materials originally used and of the technical history of aeronautics. This work reports a thorough study of aluminium-based alloy parts collected on a Breguet aeroplane dating from the 1950s, during its recent renovation. Thanks to an approach coupling multi-scale material characterisation and research in archives, information on the industrial knowledge is revealed. Several historic grades of aluminium-based alloys were found, namely A-U4G, A-U4G1, and A-U3G, depending on the role of the part. Similarly, different protective coatings were identified (anodic oxidation, primers, and paintings), depending on the role of the metallic part and its location in the plane. Knowledge of the materials from bulk metal to the coated surface is necessary for good conservation practices regarding aeronautical heritage artefacts. Related documents and archives also fundamentally help in understanding such complex artefacts.  相似文献   

Complementing subjective with objective data in analysing expertise: A machine-learning approach applied to badminton     

Olivier Dieu  Christophe Schnitzler  Clément Llena  François Potdevin 《Journal of sports sciences》2020,38(17):1943-1952

ABSTRACT

This study aimed to assess which combination of subjective and empirical data might help to identify the expertise level. A group of 10 expert coaches classified 40 participants in 5 different expertise groups based on the video footage of the rallies. The expertise levels were determined using a typology based on a continuum of 5 conative stages: (1) structural, (2) functional, (3) technical, (4) contextual, and (5) expertise. The video allowed empirical measurement of the duration of the rallies, and tri-axial accelerometers measured the intensity of the player’s involvement. A principal component analysis showed that two dimensions explained 54.9% of the total variance in the data and that conative stage and empirical parameters during rallies (duration, intensity of the game) were correlated with axis 1, whereas duration and acceleration data between rallies were correlated with axis 2. A random forest algorithm showed that among the parameters considered, acceleration, duration of the rallies, and time between rallies could predict conative stages with a prediction accuracy above possibility.

This study suggests that performance analysis benefits from the confrontation of subjective and objective data in order to design training plans according to the expertise level of the participants.  相似文献   

How do parenting concepts vary within and between the families?     

Isabelle Roskam  Jean Christophe Meunier 《European Journal of Psychology of Education - EJPE》2009,24(1):33-47

How do parenting concepts vary within and between the families? The present study regards parenting as a complex family process by considering three concepts of parenting: styles, differential treatment and coparenting consistency. A main question was addressed: whether and how these parenting concepts vary within the families towards siblings or between the two parents, and between the families according to the child's, the parent's and the family's characteristics? The parenting concepts were computed from the EPEP questionnaire (Meunier &; Roskam, 2007) in a sample of 101 non-divorced families: 101 mothers and 101 fathers of two siblings from 6- to 12-years-old. The parenting concepts were found to vary within the families towards two siblings and between the mother and the father. They were also found to vary between the families according to the child's age and personality traits as well as a function of the parent's educational level and the number of siblings.  相似文献