The timing and magnitude of upper body muscular activity during a field hockey hit

The aim of this study was to investigate the contributions to stick motion in the field hockey hit by monitoring muscle activity in the arms and trunk and synchronising these with arm and stick kinematics. The hits of ten male, university-level field hockey players were analysed. Whilst their interpretation is complicated by the closed kinetic loop formed by the arms and stick, the data collected here represent a step forward in establishing the contributions from muscular activity and segmental interactions to the field hockey hit. This study has shown that EMG analysis alone is not sufficient to explain the nature of muscular activity patterns and that the temporal aspects of EMG need to be examined in combination with kinematic data to ascertain the role of muscular activity during movement

The timing and magnitude of muscular activity patterns during a field hockey hit

The field hockey hit is one of the most important skills used in the game. However, due to the paucity of empirical research, little is known about the biomechanics of this movement. Muscular activation patterns have been shown to be major contributing factors to performance variables in similar swinging motions in golf, tennis and baseball but debate remains about which muscles are contributing to and controlling such motions. Moreover, muscle studies have typically neglected the contribution to movement from segmental interactions and have not related muscle activity to the three-dimensional kinematics of the swing. The aim of this study was to investigate the contributions from muscular activity and from segmental interactions to the hits of ten male, university-level field hockey players. The activity of sixteen upper body and trunk muscles was monitored using surface electromyography alongside synchronized three-dimensional kinematics of the upper body and hockey stick motions. Surface electromyographic signals were recorded at 2000Hz bilaterally from the biceps brachii, triceps brachii, the anterior and posterior deltoids, the upper trapezius, the latissimus dorsi and the sternal and clavicular pectoralis major muscles. Three-dimensional kinematic data were collected at 240Hz and each hockey hit was broken down into four phases of the backswing, the early forward swing, acceleration and the early follow-through. These kinematic and electromyographic data were then synchronised and temporally normalised before the electromyographic data were normalised to relative maximal reference contractions. Right anterior deltoid, right pectoralis major and bilateral latissimus dorsi activity initiates the downswing of the hockey hit, causing the early acceleration of the arms. Segmental interactions, due to these accelerations, cause the hockey stick to lag and the wrists to ‘cock’. A combination of left anterior deltoid, left latissimus dorsi and bilateral pectoralis major activity continue to accelerate the shoulders during the downswing whilst elbow musculature appears to control the effects of segmental interactions. These segmental interactions then become involved in wrist ‘uncocking’ as the stick accelerates towards impact with the ball. The effects of muscular activity and segmental interactions cause the right elbow to flex then extend, whereas the left elbow demonstrates a more constant degree of extension throughout the hit. Both wrists display the same pattern of ‘cocking’ then ‘uncocking’. These combined patterns lead the left arm and stick system to function as a double pendulum whilst the right arm and stick more closely resemble a triple pendulum

Vibration analysis of a circular plate in interaction with an acoustic cavity leading to extraction of structural modal parameters

When carrying out vibration health monitoring (VHM) of a structure it is usually assumed that the structure is in the absence of fluid interaction and that any environmental effects which can cause changes in natural frequency either remain constant or are negligible. In certain cases, this condition cannot be assumed and therefore it is necessary to extract values of natural frequencies of the structure for the condition with no fluid interaction from those values measured. This paper considers the case of a thin circular plate in contact with a fluid cavity giving rise to strong structural/fluid vibration interaction. The paper details the free vibration analysis of the coupled system and through consideration of modal energy, illustrates how the affined modes of vibration of the plate and the fluid can be qualitatively described. The paper then introduces a method by which the natural frequencies of the plate in the absence of fluid interaction can be obtained from those of the plate in interaction with the fluid

The Chemistry of some Di- and Tri-Phenylmethane dyes

Two series of dyes have been prepared: a comprehensive series of novel, unsymmetrical Malachite Green type dyes containing different amino substituents in the 4-positions of the phenyl rings and a series of symmetrical Michier's Hydrol Blue type dyes. Both series of dyes have been synthesised from the relevant carbinols or hydrols. The amino substituents used were dimethylamino, diethylamino, pyrrolidino, piperidino, morpholino, thiomorpholino and N-methylpiperazino. The rates of ailcalirie hydrolysis of the dyes at various hydroxide ion concentrations and temperatures have been investigated with a view to elucidating the reaction mechanism and the nature of substituent effects. The rate data obtained for each dye studied have been used to obtain thermodynamic activation parameters and to test the applicability of an isokinetic relationship in the dye systems. The various methods of computation and their results have been compared and discussed in relation to literature data for similar dyes. A stopped-flow technique was used for the kinetic investigation of the fast reactions associated with the unstable dyes studied. The analysis of kinetic data using single substituent parameter regression techniques has enabled substituent constants for piperidine, thiomorpholine and N-methylpiperazine to be interpolated. The steric and electronic effects of the terminal amino substituents on the visible absorption spectra of the dyes have been examined in solvents of varying acidity. The steric and electronic symmetry of the Malachite Green type dyes has been investigated and is discussed. The results from the spectral investigation and the kinetic study indicate that diphenylmethane dyes are considerably less stable than the corresponding triphenylmethane dyes and the reasons for this behaviour are discussed. In addition, piperidino, morpholino, thiomorpholino and N-methylpiperazino are less able to stabilise a dye by electron donation than dimethylamino, diethylamino and pyrrolidino and the reasons for this behaviour are also discussed. The 'H and 13C nmr spectra of the dyes and carbinols have been recorded. Certain chemical shifts have been used to determine the relative electron donor ability of the terminal amino groups. The results from the 'H and 13C nmr spectra are discussed in relation to the steric and electronic effects of the heterocycic moieties

Good infinity : Hegel, Levinas and the accomplishment of ethical life

This study presents a critique of the social and political thought of Emmanuel Levinas. We aim to demonstrate that Levinas' hostile characterisation of Hegel's System serves to disguise a latent 'Hegelian' dimension in his own thought. Levinas' covert Hegelianism has essentially three aspects: first, Levinas, like Hegel, advances a post-critical concept of the infinite; second, his philosophical discourse bears a strong family resemblance to Hegel's speculative logic: and, third, notwithstanding his protests to the contrary, his philosophy exhibits a systematic structure (in the speculative sense of the term). By identifying these speculative motifs in Levinas' work we show, first, that it is possible to subject Levinas to an immanent Hegelian critique and we then proceed to execute it. The dominant trend in Levinasian interpretation, follows Derrida, and tends to overlook the significance of Levinas' concept of society. We aim to show, however, that the notion of a visible ethical community is at the centre of Levinas' philosophy. Moreover, we attempt to demonstrate that Levinas’ concept of an ethical community is ultimately incompatible with the subjective principle underlying modem social and political life. This in turn leads Levinas to violate his own emphasis on respecting the absolute alterity of the Other. Finally, we attempt to show that Hegel's System provides a way of redeeming the ambition of Levinas' philosophy, while avoiding its negative implications

The effects of augmented biofeedback on novel motor-task learning

Biofeedback has been shown to be an influential part of skill acquisition and performance, however, the use of biofeedback for novice, sports specific skill learning has not been assessed. Non-rowers (n=3) performed a 10-minute, novel-rowing task, where joint and rowing ergometer kinematics recorded. Following six non-instructed, subjective reinforcement sessions, participants completed a further six sessions whilst receiving real-time biofeedback. The results show that all subjects changed their rowing technique, moving towards the pattern prescribed by the biofeedback intervention. The elbow remained in greater extension until later in the pull, which induced changes in the temporal aspects of both knee and lumbar spine kinematics

Key issues in rural health: perspectives of health service providers in Queensland

The Centre for Rural and Remote Area Health (CRRAH) held interactive research workshops in eight towns in Southern Queensland. The purpose of the workshops was to determine what health providers considered were major issues affecting their service and for these results to inform future research strategy of CRRAH. Over 150 organisations identified as either providing health services or having a significant interest in health provision in one or more of the targeted towns were invited to attend. The workshops used the nominal group technique to identify what the participants considered were key health issues in the geographical area in which they worked. These issues were then prioritised by the participants. Thematic analysis of the issues generated a ranking of themes by importance. Results were compared with a similar exercise undertaken in 2003. Participants from organisation directly involved with health care were complemented at the workshops by representatives from local government, the police service and church groups. A total of 85 participants representing 47 services and 41 different organisations attended the eight workshops. Issues generated by the participants were pooled into seventeen themes. Workforce issues were by far the major concern of health providers. Recruitment and retention of health workers were a major concern. The other four highest ranked themes across all workshops were mental health, access to health services, perceptions and expectations of consumers of health services and interagency cooperation. Aged care was an additional theme that generated a lot of concern at several of the workshops. The workshops provided important information to CRRAH for developing research strategy. Additionally, several new alliances among health providers were developed which will support sharing of information and resources. The workshops enabled rural and remote organisations to meet and identify the key health issues and supported research planning. Much need alliances among health providers were forged and collaborative research avenues are being explored. The workshop forum is an excellent means of information exchange