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Max C. Stuelcken Daniel B. Mellifont Adam D. Gorman Mark G.L. Sayers 《Journal of sports sciences》2016,34(16):1516-1522
This study involved a systematic video analysis of 16 anterior cruciate ligament (ACL) injuries sustained by elite-level netball players during televised games in order to describe the game situation, the movement patterns involved, the player’s behaviour, and a potential injury mechanism. Eight of the ACL injuries were classified as “indirect contact” and eight as “non-contact”. Two common scenarios were identified. In Scenario A the player was jumping to receive or intercept a pass and whilst competing for the ball experienced a perturbation in the air. As a result the player’s landing was unbalanced with loading occurring predominantly on the knee of the injured side. In Scenario B the player was generally in a good position at ground contact, but then noticeably altered the alignment of the trunk before the landing was completed. This involved rotating and laterally flexing the trunk without altering the alignment of the feet. Apparent knee valgus collapse on the knee of the injured side was observed in 3/6 Scenario A cases and 5/6 Scenario B cases. Players may benefit from landing training programmes that incorporate tasks that use a ball and include decision-making components or require players to learn to cope with being unbalanced. 相似文献
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AbstractStroke-coordination and symmetry influence the force fluctuations within any net drag force profile. The aim of this study was to analyse elite (FINA points 938) backstroke swimmers stroke-coordination using an instantaneous net drag force and timing protocols using a symmetry index tool. Ten male and nine female elite backstroke swimmers completed three maximum speed trials and five maximum speed net drag force swimming trials. Net drag force was measured using an assisted motorised dynamometer device. Each trial was filmed using three genlocked 50 Hz cameras, synchronised to the net drag force output from the force-platform. This methodology enabled the comparison of stroke-coordination timing symmetry index to net drag force symmetry index. The timing symmetry index and net drag force symmetry index yielded different results, the timing reflects the stroke-coordination, whilst the force index identified the effectiveness of the stroke. The only variable that was significantly different when comparing left and right stroke patterns was the location of minimum net drag forces. Conversely, gender influenced the location of maximum net drag force. Relationship analysis identified that location of maximum net drag force production was the only variable to correlate with speed within this cohort. Backstroke arm coordination was minimally influenced by gender. 相似文献
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Mark G. L. Sayers Caroline Bachem Pascal Schütz William R. Taylor Renate List Silvio Lorenzetti 《Journal of sports sciences》2020,38(9):1000-1008
ABSTRACTThis research assessed the influence of various heel elevation conditions on spinal kinematic and kinetic data during loaded (25% and 50% of body weight) high-bar back squats. Ten novice (mass 67.6 ± 12.4 kg, height 1.73 ± 0.10 m) and ten regular weight trainers (mass 66.0 ± 10.7 kg, height 1.71 ± 0.09 m) completed eight repetitions at each load wearing conventional training shoes standing on the flat level floor (LF) and on an inclined board (EH). The regular weight training group performed an additional eight repetitions wearing weightlifting shoes (WS). Statistical parametric mapping (SPM1D) and repeated measures analysis of variance were used to assess differences in spinal curvature and kinetics across the shoe/floor conditions and loads. SPM1D analyses indicated that during the LF condition the novice weight trainers had greater moments around L4/L5 than the regular weight trainers during the last 20% of the lift (P < 0.05), with this difference becoming non-significant during the EH condition. This study indicates that from a perspective of spinal safety, it appears advantageous for novice weight trainers to perform back squats with their heels slightly elevated, while regular weight trainers appear to realize only limited benefits performing back squats with either EH or WS. 相似文献
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R.R. Sayers 《Journal of The Franklin Institute》1925,199(2):269-270
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New cricket bats need to be ‘knocked in’ prior to use, but just what this process does to the surface fibres of the bat is
unknown and unquantified. One quantitative measurement of knock-in is the resultant surface hardness of the bat, and this
paper describes knock-in tests to determine the surface hardness following differing durations of knock-in. The design of
a cricket bat knock-in machine is first described. This takes the form of a cradle in which a cricket bat can be secured horizontally
and then traversed at constant speeds in two mutually perpendicular directions while at the same time being struck with constant
force by a cricket ball. The traverses are driven by lead screws, the motors of which can be independently switched on or
off. The traverse distance can be varied with adjustable limit switches and relays that reverse the direction of rotation
of the lead screws when activated. The cricket ball is attached to a rod that is lifted cyclically by a cam against a coil
spring extension, and then allowed to fall under that force to impact on the bat surface. The impact (knocking-in) force was
measured by a previously calibrated strain gauge attached to the rod holding the cricket ball. By judicious setting of the
limit switches, selected areas of the bat surface were continuously knocked in for periods varying from 1 to 4 hours. After
knocking in, the surface hardness was measured in accordance with British Standard 373 using a penetrator designed in accordance
with the same standard. Analysis of the load/penetration curves shows an increase in surface hardness with knock duration.
Photographs of the cell structure of the surface wood, obtained using a scanning electron microscope, show that under knock-in
conditions, the wood cells collapse to form a mesh-like hardened layer which increases in hardness with increase in knock-in
duration. 相似文献
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ABSTRACTWe theorise an interdisciplinary arts practice university course and consider the forms of educational imaginary challenged by our curriculum. We argue for the disruptive and generative potential of what we call diffractive pedagogy as an example of the type of learning that can take place when materiality and entanglement are considered as vital constituents. Through self-expression and interweaving across disciplinary boundaries, the potential to produce, embody and theorise simultaneously can be realised. Student bodies do not exist in isolation from one another, or from the environment. It is indeed impossible to separate the dancer from the dance, the teacher from the student, and the bodies from the environments and objects to which they relate. This being true, our student body reproduced our teaching bodies as abject, as messy and peripheral to their imaginings of university education. Materially, student bodies remade the limits to which their consciousness was imaginatively drawn. Through our embodied work, unconscious change began the processes of affecting students’ imaginaries of university education. 相似文献
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