26 resultados para head movement


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Introduction: Neck injuries are common in high performance combat pilots and have been attributed to high gravitational forces and the non-neutral head postures adopted during aerial combat maneuvers. There is still little known about the pathomechanics of these injuries.

Methods: Six Royal Australian Air Force Hawk pilots flew a sortie that included combinations of three +Gz levels (1, 3, and 5) and four head postures (Neutral, Turn, Extension, and Check-6). Surface electromyography from neck and shoulder muscles was recorded in flight. Three-dimensional measures of head postures adopted in flight were estimated postflight with respect to end-range of the cervical spine using an electromagnetic tracking device.

Results: Mean muscle activation increased significantly with both increasing +Gz and non-neutral head postures. Check-6 at +5 Gz (mean activation of all muscles = 51% MVIC) elicited significantly greater muscle activation in most muscles when compared with Neutral, Extension, and Turn head postures. High levels of muscle co-contraction were evident in high acceleration and non-neutral head postures. Head kinematics showed Check-6 was closest to end-range in any movement plane (86% ROM in rotation) and produced the greatest magnitude of rotation in other planes. Turn and Extension showed a large magnitude of rotation with reference to end-range in the primary plane of motion but displayed smaller rotations in other planes.

Discussion:
High levels of neck muscle activation and co-contraction due to high +Gz and head postures close to end range were evident in this study, suggesting the major influence of these factors on the pathomechanics of neck injuries in high performance combat pilots.

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This article is a study of the response of the Australian government under Robert Menzies to the emergence of the Afro-Asian movement in the mid-1950s, especially the element of the non-aligned nations, which culminated in the Bandung meeting of April 1955. Non-alignment and anti-colonialism posed direct threats to the Menzies government's plans for the defence of Southeast Asia and its foreign policy for the region. The study of the Australian response to the Bandung meeting reveals the different legacies which European imperialism left behind in Australia compared with its neighbours in south and east Asia.

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Recognizing a class of movements as belonging to a "nominal" action category, such as walking, running, or throwing, is a fundamental human ability. Three experiments were undertaken to test the hypothesis that common ("prototypical") features of moving displays could be learned by observation. Participants viewed moving stick-figure displays resembling forearm flexion movements in the saggital plane. Four displays (presentation displays) were first presented in which one or more movement dimensions were combined with 2 respective cues: direction (up, down), speed (fast, slow), and extent (long, short). Eight test displays were then shown, and the observer indicated whether each test display was like or unlike those previously seen. The results showed that without corrective feedback, a single cue (e.g., up or down) could be correctly recognized, on average, with the proportion correct between .66 and .87. When two cues were manipulated (e.g., up and slow), recognition accuracy remained high, ranging between .72 and .89. Three-cue displays were also easily identified. These results provide the first empirical demonstration of action-prototype learning for categories of human action and show how apparently complex kinematic patterns can be categorized in terms of common features or cues. It was also shown that probability of correct recognition of kinematic properties was reduced when the set of 4 presentation displays were more variable with respect to their shared kinematic property, such as speed or amplitude. Finally, while not conclusive, the results (from 2 of the 3 experiments) did suggest that similarity (or "likeness") with respect to a common kinematic property (or properties) is more easily recognized than dissimilarity.

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The article explores the ways knowledge and space are co-produced performatively through bodily movement in an examination of the Maltese megaliths the first complex stone structures in the world. It is argued that knowledge is best seen as spatialized narratives of human actions and objects as materialized forms of those spatial narratives. Rewriting our social and historical narratives so that the performativity of place, space and knowledge is restored opens new possibilities for rethinking the social and material order.

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Australian and English print media are actively engaged in producing reports that claim to find the 'best schools', the 'real state of education', and 'star head teachers'. This article considers the production of knights and dames, maverick heads and struggling schools. It argues that some of these stories are clearly the products of departmental press bureau activities and policy agendas. It shows, however, that even those stories intended to critique government policy support paradoxically a notion of the singular importance of the headship and the virtues of heroic leadership. It is suggested that the simulacrum of the heroic head works as a normative disciplinary device for performative and market practices and is singularly off-putting to both serving and aspirant school leaders.

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The velocity at which a golf club impacts with a golf ball is known as club head speed. Although club head speed has been used to measure performance changes in a number of golf studies, it has not been validated as a golf performance measure. As handicap is the usual measure of performance, the purpose of this study was to investigate the relationship between club head speed and handicap, and to determine whether club head speed at impact is a valid measure of golfing performance. Forty-five male golfers aged 18–80 years, all with registered golfing handicaps (2–27), participated in this study. Each golfer performed 10 golf swings captured by a high-speed camera. Golfers' club head speeds were determined using Video Expert 2, a biomechanical computer program. Golfers with a lower handicap (ie, a better skill level) had faster club head speeds than higher handicap golfers. Linear regression analysis found club head speed to be highly correlated with handicap (r= 0.950). This relationship was described by the equation: In (club head speed)= 4.065 − 0.0214 x handicap. In conclusion, this study has shown that club head speed is a valid indicator of performance in golfers and may therefore be a useful performance measure in future laboratory-based studies.

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Consumer and patient advocacy groups (PAGs) are important participants in the politics of pharmaceuticals. Yet very little is known about the precise nature and extent of their influence. It is argued in this article that PAGs fulfil a mixed role within the health system at national and transnational levels, and that they are at times fully incorporated into economic and political power structures. Their frequent dependence on pharma industry funding is of particular concern. PAGs provide a means of direct industry interaction with the final customer, thereby partially bypassing and putting additional pressure on doctors and regulators. The article presents the case for research to establish a better empirical base for discussions about the role of PAGs within contemporary neo-liberal governance structures.

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John Gough explains how to turn an ordinary set of dominoes into games of mystery, movement and strategy.

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Many union leaders and observers of unionism in industrially advanced countries have recently argued for stronger links between unions and social movements but their arguments leave the nature of social movements underspecified. This article reviews the literature on social movements and argues in favour of a minimalist theory of the social actor rather than choose between American and European approaches to studying social movements. Both Melucci's European approach and McAdam, Tarrow, and Tilly's American approach to integrating the European and American schools of thought on social movements are inadequate to the task of specifying social-movement unionism. Hindess's minimalist theory of the social actor and articulated arenas of conflict offers a stronger approach to understanding social-movement unionism and appreciating its strategic pertinence in particular times and places. Two episodes of contention in Sweden illustrate the advantages of a minimalist theory of articulated social-movement unionism.

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From a European perspective, the wide-ranging social, economic, and political effects of networked computers have generated tensions between 'new' social movements and the 'old' labour movement. From an American perspective on social movements, there is no such tension between old and new social movements. A study of social-movement unionism in Sweden offers a interesting means of testing this emerging American perspective against the European perspective because the labour movement has long been particularly effective and networked technology has been embraced whole-heartedly throughout all aspects of the society, the economy, and the polity. The paper introduces the contrasting European and American perspectives on social movements and presents examples of the practice of social-movement unionism among Swedish social democrats, unionists, and diverse local activists. These examples support conclusions that eschew utopian theories of 'cyberunionism' in favour of developing a theory of articulated unionism in which local unions branches articulate vertically with national and global union bodies, and articulate horizontally with social movements in other arenas of conflict.

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Survey-based research explored the moderating effects of "exposure" to the Australian free-to-air telecast of Athens 2004 and "interest" in Olympic Games in developing behavioral intentions to visit Greece in the future. Differences were found between groups with low and high levels of exposure to the telecast, and also between groups with high levels of interest in the Olympic Games, but these were only marginal. When the combinatorial influences of these two variables were considered simultaneously, their effects were generally synergistic. The article calls for further research on this area of mega-events, as the results, while of significance, provide food to continue the broader debate on the role of mega-events in developing tourism to their host destinations after their staging.