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61.
The highly unsteady flow around a rowing blade in motion is examined using a three-dimensional computational fluid dynamics
(CFD) model which accounts for the interaction of the blade with the free surface of the water. The model is validated using
previous experimental results for quarter-scale blades held stationary near the surface in a water flume. Steady-state drag
and lift coefficients from the quarter-scale blade flume simulation are compared to those from a simulation of the more realistic
case of a full-scale blade in open water. The model is then modified to accommodate blade motion by simulating the unsteady
motion of the rowing shell moving through the water, and the sweep of the oar blade with respect to the shell. Qualitatively,
the motion of the free surface around the blade during a stroke shows a realistic agreement with the actual deformation encountered
during rowing. Drag and lift coefficients calculated for the blade during a stroke show that the transient hydrodynamic behaviour
of the blade in motion differs substantially from the stationary case. 相似文献
62.
63.
Joshua H. Guy Andrew M. Edwards Catherine M. Miller Glen B. Deakin David B. Pyne 《Journal of sports sciences》2017,35(16):1622-1628
Prospective application of serum cytokines, lipopolysaccharide (LPS), and heat shock proteins (eHSPs) requires reliable measurement of these biomarkers that can signify exercise-induced heat stress in hot conditions. To accomplish this, both short-term (7 day) reliability (at rest, n = 12) and the acute responsiveness of each biomarker to exercise in the heat (pre and post 60-min cycling, 34.5°C and 70% RH, n = 20) were evaluated. Serum was analysed for the concentration of C-reactive protein (CRP), interleukin-6 (IL-6), heat shock protein 72 (eHSP72), immunoglobulin M (IgM) and LPS. Test–retest reliability was determined as the coefficient of variation (CV). Biomarkers with the least short-term within-participant variation were IL-6 (19%, ±20%; CV, ±95% confidence limits (CL)) and LPS (23%, ±13%). Greater variability was observed for IgM, eHSP72 and CRP (CV range 28–38%). IL-6 exhibited the largest increase in response to acute exercise (95%, ±11%, P = < 0.001) and although CRP had a modest CV (12%, ±7%), it increased substantially post-exercise (P = 0.02, ES; 0.78). In contrast, eHSP72 and LPS exhibited trivial changes post-exercise. It appears variation of common inflammatory markers after exercise in the heat is not always discernible from short-term (weekly) variation. 相似文献
64.
The 100 ms ruling for false start disqualification at athletic competitions governed by the International Association of Athletics Federations has been in force since the early 1990s. Throughout this period, there have been marked changes to the rules that govern the disqualification of athletes from sprint events incorporating starts from blocks. This study analysed all available World and European Championship response-time (RT) data from 1999 to 2014 to examine effects of rule changes on competition RT at major championships. The exponentially modified Gaussian distribution was used to model RT and make comparisons relative to athletes’ sex, ruling periods and competition rounds. Revised RT thresholds of 115 ms and 119 ms were identified for men and women, respectively, indicating that the current 100 ms rule could result in some false starts not being detected in competitive athletics. The study proposes that when using existing International Association of Athletics Federations approved systems, the false start detection threshold should be increased and that men and women athletes should have different thresholds because of substantial evidence of a sex-based difference in RT in elite-standard athletes. 相似文献
65.
The purpose of this study was to investigate the temporal phases of the archery shot cycle that distinguish the arrows distance from centre, in an attempt to understand critical factors that affect performance. Fifteen archers of varying ability each performed 30 shots at 18 m. Fourteen potential predictor variables were measured for statistical modelling by stepwise multiple linear regression. The results show that pre-shot time (pre-performance routine), follow-through time (post-performance routine), aiming time, speed of the arrow and the %variation in clicker-release time, account for 7.7% of the variation in predicting shot performance. The results have implications for practice demonstrating factors that coaches should focus on to develop their athletes. Further work on pre-, but more importantly, post-performance routines are needed generally within sport research as they are lacking and have been shown to be important contributing factors in a number of sports. 相似文献
66.
Andrew Miller Stephen Harvey David Morley Roland Nemes Maggie Janes Narelle Eather 《Journal of sports sciences》2017,35(18):1846-1857
This study evaluated whether exposing junior netball players to greater amounts of competition relevant activity (playing form activity) had an effect on game play outcomes and session involvement. A group-randomised controlled trial in one junior netball club in the Hunter Region, NSW, Australia. Ninety female athletes (mean age = 9.04 years, SD 1.53) were randomised by team (n = 11) into the intervention (n = 41) or 9-week wait-list control (n = 49) condition. The Professional Learning for Understanding Games Education into Sport (PLUNGE into Sport) programme was undertaken in the first half of nine training sessions (9 × 30 min). The intervention exposed athletes to playing form activity through a coach development programme within training sessions. Athletes’ decision-making, support and skill outcomes during a small-sided invasion game, and session involvement (pedometer step/min), were measured at baseline and 9-week follow-up. Linear mixed models revealed significant group-by-time intervention effects (P < 0.05) for decision-making (d = 0.4) and support (d = 0.5) during game play, and in-session activity (d = 1.2). An intervention exposing athletes to greater levels of playing form activity, delivered via a coach education programme, was efficacious in improving athlete decision-making and support skills in game play and increasing athlete involvement during sessions. 相似文献
67.
Andrew Post J. Michio Clark D. G. E. Robertson T. Blaine Hoshizaki Michael D. Gilchrist 《Sports Engineering》2017,20(2):111-119
Brain injury research in sport employs a variety of physical models equipped with accelerometers. These acceleration signals are commonly processed using filters. The purpose of this research was to determine the effect of applying filters with different cutoff frequencies to the acceleration signals used as input for finite element modeling of the brain. Signals were generated from reconstructions of concussion events from American football and ice hockey in the laboratory using a Hybrid III headform. The resulting acceleration signals were used as input for the University College Dublin Brain Trauma Model after being processed with filters. The results indicated that using a filter with a cutoff of 300 Hz or higher had little effect on the resulting strain measures. In some cases there was some effect of the filters on the peak linear (8–30g) and rotational measures (1000–4000 rad/s2), but little effect on the finite element strain result (approximately 2–6 %). The short duration and high magnitude accelerations, such as the puck impact, were most affected by the cutoff frequency of different filters. 相似文献
68.
Alis Bonsignore Shannon S. D. Bredin Holly Wollmann Barb Morrison Andrew Jeklin Lauren Buschmann 《European Journal of Sport Science》2017,17(4):441-446
There is inconclusive evidence concerning the effects of routine participation in ultra-endurance events on cardiovascular disease (CVD) risk. Arterial compliance is a reliable, non-invasive, and effective tool for evaluating CVD risk. The purpose of this research was to examine if race length influences acute changes in arterial compliance following an ultra-marathon event. A total of 46 ultra-marathon runners were recruited including 21 participants (39.8?±?8.3?years, 6 females) in the 80-km event and 25 participants (43.7?±?9.8?years, 3 female) in the 195-km event. Arterial compliance was measured via radial applanation tonometry (CR-2000, HDI) for diastolic pulse contour analysis before and following the race. Significant between-group differences were found for changes in large arterial compliance with a decrease (increase in stiffness) following the 195-km event and an increase following the 80-kilometre event (p?<?.05). Longer race lengths are associated with greater reductions in large arterial compliance following recreational ultra-marathon running. Assessment of arterial compliance might be a useful prognostic tool to assess the long-term risk of CVD among ultra-marathon runners. 相似文献
69.
Justin X. Nicoll Andrew J. Galpin Donald B. Thomason Christopher A. Moore 《European Journal of Sport Science》2017,17(9):1194-1202
Purpose: There is a paucity of research investigating the expression of mitogen-activated protein kinases (MAPK) in chronically trained (CT) athletes. Thus, it is unclear how MAPK may contribute to performance and muscle adaptation in CT subjects. The purpose of this study was to determine MAPK total protein, and phosphorylated expression of extracellular signal-regulated kinases 1 and 2 (ERK1/2), c-Jun N-terminal kinase (JNK), and p38-MAPK (p38) between untrained, and chronically trained runners. Methods: Tissue samples were analysed from sedentary (SED; n?=?5) controls and chronically trained runners (CT; n?=?5). Resting muscle biopsy samples were analysed for total-MAPK – and ratio of phosphorylated/total (p-MAPK) – ERK1/2, JNK, and p38-MAPK via western blotting. Mann–Whitney U tests and effect sizes were utilized to determine differences in total MAPK protein content and phosphorylation status between SED and CT subjects. Results: There was no difference in total-MAPK expression between SED and CT (p?>?.05). p-p38-MAPK tended to be greater for CT compared to SED (p?=?.07). There were moderate effect sizes of decreased pERK/total-ERK (d?=??0.69) and increased pJNK/total-JNK (d?=?0.54) in CT compared to SED. There was a positive correlation between p-p38-MAPK/total-MAPK and the percentage of type I fibres (r?=?0.73, p?=?.016). Conclusion: Contrary to previous studies, chronic endurance training does not greatly influence total MAPK protein expression in chronically trained runners. However, resting phosphorylation of p38-MAPK may contribute to enhanced oxidative metabolism at chronically trained levels. These alterations are likely involved in the different physiological adaptations that occur following long-term training or at highly competitive levels. 相似文献
70.
Emer Van Ryswyk Richard Weeks Laura Bandick Michaela O’Keefe Andrew Vakulin Peter Catcheside 《European Journal of Sport Science》2017,17(2):144-151
Objectives: To improve well-being and performance indicators in a group of Australian Football League (AFL) players via a six-week sleep optimisation programme. Design: Prospective intervention study following observations suggestive of reduced sleep and excessive daytime sleepiness in an AFL group. Methods: Athletes from the Adelaide Football Club were invited to participate if they had played AFL senior-level football for 1–5 years, or if they had excessive daytime sleepiness (Epworth Sleepiness Scale [ESS] >10), measured via ESS. An initial education session explained normal sleep needs, and how to achieve increased sleep duration and quality. Participants (n?=?25) received ongoing feedback on their sleep, and a mid-programme education and feedback session. Sleep duration, quality and related outcomes were measured during week one and at the conclusion of the six-week intervention period using sleep diaries, actigraphy, ESS, Pittsburgh Sleep Quality Index, Profile of Mood States, Training Distress Scale, Perceived Stress Scale and the Psychomotor Vigilance Task. Results: Sleep diaries demonstrated an increase in total sleep time of approximately 20?min (498.8?±?53.8 to 518.7?±?34.3; p?<?.05) and a 2% increase in sleep efficiency (p?<?0.05). There was a corresponding increase in vigour (p?<?0.001) and decrease in fatigue (p?<?0.05). Conclusions: Improvements in measures of sleep efficiency, fatigue and vigour indicate that a sleep optimisation programme may improve athletes’ well-being. More research is required into the effects of sleep optimisation on athletic performance. 相似文献