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The aims of this study were to investigate the energy build-up and dissipation mechanisms associated with using an arm swing in submaximal and maximal vertical jumping and to establish the energy benefit of this arm swing. Twenty adult males were asked to perform a series of submaximal and maximal vertical jumps while using an arm swing. Force, motion and electromyographic data were recorded during each performance and used to compute a range of kinematic and kinetic variables, including ankle, knee, hip, shoulder and elbow joint powers and work done. It was found that the energy benefit of using an arm swing appears to be closely related to the maximum kinetic energy of the arms during their downswing, and increases as jump height increases. As jump height increases, energy in the arms is built up by a greater range of motion at the shoulder and greater effort of the shoulder and elbow muscles but, as jump height approaches maximum, these sources are supplemented by energy supplied by the trunk due to its earlier extension in the movement. The kinetic energy developed by the arms is used to increase their potential energy at take-off but also to store and return energy from the lower limbs and to "pull" on the rest of the body. These latter two mechanisms become more important as jump height increases with the pull being the more important of the two. We conclude that an arm swing contributes to jump performance in submaximal as well as maximal jumping but the energy generation and dissipation sources change as performance approaches maximum.  相似文献   
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In studying the historical development of early years provision, a clear factor in raising its profile was the growth in scientific study of children, especially the reception and interpretation of Piaget's research. For an understanding of how the mediation of new thinking and new discoveries influenced students and teachers, textbooks provide an important documentary source, but evidence is also available through oral history in the living memories of practitioners themselves. This paper draws on the testimony of early years teachers who began their careers between 1927 and 1955 and continued teaching into the 1960s and 1970s. The account below begins with reflections on psychology and education in the early decades of the twentieth century drawn from a 1936 conference organised by the Nursery School Association of Great Britain, and from a widely used textbook that represents the gradual trend towards ‘fragmentation’ of educational theory into a multiplicity of disciplines. Reference is then made to two popular textbooks by prominent Froebelians, Brearley and Hitchfield, and by Ruth Beard illustrating the growing influence of Piaget as a post facto rationale for a pedagogy that was proceeding by instinct. Walkerdine, Lister and Hall are researchers who have investigated from various angles the impact of Piagetian psychology on primary practice, but the process whereby this translation from the laboratory to the classroom takes place is one that demands further investigation. Vital evidence lies in the living memories of early years teachers whose careers spanned the 1930s to the 1970s and a rich quality and personal texture of the data is apparent as retired early years teachers recounted their professional careers. It offers a more complex account than the grand narratives that historians have traditionally compiled from purely documentary evidence centring on great thinkers, key texts and policy initiatives. The role of in‐service education was clearly important in the experiences recalled in this paper. Above all we find evidence of a distinctive shift in teacher–child relationships over that historical period and of the contribution made to this by psychological theory, epitomised in the figure of Piaget and in his focus on the individual learner.  相似文献   
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The cadence that maximises power output developed at the crank by an individual cyclist is conventionally determined using a laboratory test. The purpose of this study was two-fold: (i) to show that such a cadence, which we call the optimal cadence, can be determined using power output, heart-rate, and cadence measured in the field and (ii) to describe methodology to do so. For an individual cyclist's sessions, power output is related to cadence and the elicited heart-rate using a non-linear regression model. Optimal cadences are found for two riders (83 and 70 revolutions per minute, respectively); these cadences are similar to the riders’ preferred cadences (82–92?rpm and 65–75?rpm). Power output reduces by approximately 6% for cadences 20?rpm above or below optimum. Our methodology can be used by a rider to determine an optimal cadence without laboratory testing intervention: the rider will need to collect power output, heart-rate, and cadence measurements from training and racing sessions over an extended period (>6 months); ride at a range of cadences within those sessions; and calculate his/her optimal cadence using the methodology described or a software tool that implements it.  相似文献   
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