Static and dynamic accuracy of a magnetic-inertial measurement unit used to provide racket swing kinematics     

Benjamin Kane Williams  Ross H. Sanders  Joong Hyun Ryu  Pitre C. Bourdon  Philip Graham-Smith  Peter J. Sinclair 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(2):202-214

Magnetic-inertial measurement units (MIMUs) are becoming more prevalent in sports biomechanics and may be a viable tool to evaluate kinematic parameters. This study examined the accuracy of a MIMU to estimate orientation angles under static conditions and dynamically from a squash racket during a forehand drive shot. A MIMU was mounted onto a goniometer and moved through 0–90°, with static data collected at 10° increments during 10 repetitions of all three axes. Typical error analyses showed the MIMU to be very reliable (TE ≤ 0.03°). MIMU accuracy was determined via intraclass correlation coefficients (ICC) (r > 0.999, p < 0.001). An ordinary least products regression showed no proportional bias and minimal fixed bias for all axes. Dynamic accuracy was assessed by comparing MIMU and optical motion capture data of squash racket swing kinematics. A MIMU was fixed onto a racket and 10 participants each hit 10 forehand shots. Mean orientation angle error at ball impact was <0.50° and ICC showed very high correlations (r ≥ 0.988, p < 0.001) for all orientations. Swing phase root mean squared errors were ≤2.20°. These results indicate that a MIMU could be used to accurately and reliably estimate selected racket swing kinematics.  相似文献   

The application of inertial measurement units and functional principal component analysis to evaluate movement in the forward 3½ pike somersault springboard dive     

Cherie Walker  John Warmenhoven  Peter J. Sinclair 《Sports biomechanics / International Society of Biomechanics in Sports》2019,18(2):146-162

Based on technological and analytical advances, the capability to more accurately and finitely examine biomechanical and skill characteristics of movement has improved. The purpose of this study was to use Inertial Measurement Units (IMUs) and Functional Principal Components Analysis (fPCA) to examine the role of movement variability (assessed via angular velocity), on 2 divers (1 international level; 1 national) performing the forward 3½ pike somersault dive. Analysis of angular velocity curves during ive-flight identified 5 fPCs, accounting for 96.5% of movement variability. The national diver’s scatter plots and standard deviation of fPC scores illustrated larger magnitudes of angular velocity variability across dive flight. For fPC1 and fPC3, magnitudes of SD variability were 282.6 and 201.5, respectively. The international diver illustrated more consistent angular velocity profiles, with clustering of fPCs scores (e.g., fPC1 & 3 = SD’s of 75.2 & 68.0). To account for lower variability in the international diver, the ability to better coordinate movement sequences and functionally utilise feedback in response to initiation of the somersault position is highlighted. Overall, findings highlight how both IMUs and fPCA can more holistically and finitely examine the biomechanical and skill characteristics of movement sequences with the capability to inform athlete development.  相似文献   

Understanding the track and field sprint start through a functional analysis of the external force features which contribute to higher levels of block phase performance     

Neil Edward Bezodis  Sean Peter Walton  Ryu Nagahara 《Journal of sports sciences》2019,37(5):560-567

This study aimed to identify the continuous ground reaction force (GRF) features which contribute to higher levels of block phase performance. Twenty-three sprint-trained athletes completed starts from their preferred settings during which GRFs were recorded separately under each block. Continuous features of the magnitude and direction of the resultant GRF signals which explained 90% of the variation between the sprinters were identified. Each sprinter’s coefficient score for these continuous features was then input to a linear regression model to predict block phase performance (normalised external power). Four significant (p < 0.05) predictor features associated with GRF magnitude were identified; there were none associated with GRF direction. A feature associated with greater rear block GRF magnitudes from the onset of the push was the most important predictor (β = 1.185), followed by greater front block GRF magnitudes for the final three-quarters of the push (β = 0.791). Features which included a later rear block exit (β = 0.254) and greater front leg GRF magnitudes during the mid-push phase (β = 0.224) were also significant predictors. Sprint practitioners are encouraged, where possible, to consider the continuous magnitude of the GRFs produced throughout the block phase in addition to selected discrete values.  相似文献   

The effect of beetroot juice supplementation on repeat-sprint performance in hypoxia     

Georgina L. Kent  Brian Dawson  Lars R. McNaughton  Gregory R. Cox  Louise M. Burke  Peter Peeling 《Journal of sports sciences》2019,37(3):339-346

This investigation assessed the effect of dietary nitrate (NO₃^?) supplementation, in the form of beetroot juice (BR), on repeat-sprint performance in normoxia and normobaric hypoxia. 12 male team-sport athletes (age 22.3 ± 2.6 y, VO_2peak 53.1 ± 8.7 mL.kg^?1.min^?1) completed three exercise trials involving a 10 min submaximal warm-up and 4 sets of cycling repeat-sprint efforts (RSE; 9 × 4 s) at sea level (CON), or at 3000 m simulated altitude following acute supplementation (140 mL) with BR (HYP_BR; 13 mmol NO₃^?) or NO₃^–depleted BR placebo (HYP_PLA). Peak (PPO) and mean (MPO) power output, plus work decrement were recorded during the RSE task, while oxygen consumption (VO₂) was measured during the warm-up. There were no significant differences observed between HYP_BR and HYP_PLA for PPO or MPO; however, work decrement was reduced in the first RSE set in HYP_BR compared with HYP_PLA. There was a moderate effect for VO₂ to be lower following BR at the end of the 10 min warm-up (ES = 0.50 ± 0.51). Dietary NO₃^? may not improve repeat-sprint performance in hypoxia but may reduce VO₂ during submaximal exercise. Therefore, BR supplementation may be more effective for performance improvement during predominantly aerobic exercise.  相似文献   

Evening electronic device use and sleep patterns in athletes     

Maddison J. Jones  Brian Dawson  Daniel F. Gucciardi  Peter R. Eastwood  Joanna Miller  Shona L. Halson 《Journal of sports sciences》2019,37(8):864-870

The present study aimed to investigate pre-sleep behaviours (including evening electronic device use) and sleep quantity in well-trained athletes. Seventy well-trained athletes (44 females, 26 males) aged 21 ± 4 y from a range of team and individual sports were asked to complete an online sleep diary for 7 days. The sleep diary included questions about pre-sleep behaviours (e.g. napping, caffeine intake), electronic device use in the 2 h prior to bedtime (e.g. type of device and duration of use) and sleep (e.g. time in bed, sleep onset latency). On average, athletes spent 8:20 ± 1:21 h in bed each night. Associations between age, time in bed and sleepiness suggested that younger athletes spent more time in bed (B = -0.05, p = 0.001) but felt sleepier (r = -0.32, p < 0.01) than older athletes. On average, athletes mostly used electronic devices for 0–30 min prior to sleep. The use of multiple devices in the evening was associated with more perceived difficulty in falling asleep (B = 0.22, p = 0.03), but no associations existed with other sleep variables. In summary, younger athletes may require later start times or improved sleep quality to resolve excessive sleepiness.  相似文献   

Visualising the Interdisciplinary Research Field: The Life Cycle of Economic History in Australia     

Claire Wright  Simon Ville 《Minerva》2017,55(3):321-340

Interdisciplinary research is frequently viewed as an important component of the research landscape through its innovative ability to integrate knowledge from different areas. However, support for interdisciplinary research is often strategic rhetoric, with policy-makers and universities frequently adopting practices that favour disciplinary performance. We argue that disciplinary and interdisciplinary research are complementary, and we develop a simple framework that demonstrates this for a semi-permanent interdisciplinary research field. We argue that the presence of communicating infrastructures fosters communication and integration between disciplines and the interdisciplinary research field to generate innovative knowledge. We apply this to the experience of economic history in Australia in the second half of the twentieth century to demonstrate the life cycle of a semi-permanent interdisciplinary research field.  相似文献   

A novel sleep optimisation programme to improve athletes’ well-being and performance     

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   

Super Bowl Sunday: A National Holiday and a Global Curiosity     

Peter Hopsicker  Mark Dyreson 《国际体育史杂志》2017,34(1-2):1-6

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Football Club Formation and the Lancashire Leisure Class, 1857–1870     

Peter Swain 《国际体育史杂志》2017,34(7-8):498-516

This paper outlines the transition from football games played for occasional amusement to a system of organized football clubs playing regular matches in Lancashire in the mid-nineteenth century. This was led by young men of an emerging Lancashire leisured class being, in the main, the public school educated sons of the northern county’s commercial and industrial elite. These families had accumulated sufficient wealth, especially in the first half of the nineteenth century, to exempt a considerable part of their population from work both at weekends and during the normal working week with football becoming an act of conspicuous consumption. Three case studies of individual clubs and leading individuals within those clubs are presented with detailed archival research carefully avoiding the teleology implicit in much historical writing of the past. It also swells the paucity of good historical material about the organization of sport at levels below national bodies. In so doing, it aims to illuminate some of the shadows in the big picture of the evolution of sport and leisure in Lancashire and Britain itself while informing the ongoing orthodox/revisionist debate into the origins of football in the nineteenth century.  相似文献   

生活方式干预对心血管疾病危险因素的影响——美国HELPS项目成果     

Peter H. Brubaker  罗曦娟  Chelsea Boltj  Shuchang Du 《北京体育大学学报》2017,40(6):48-53

摘要：心血管疾病（CVD）一直是全世界最主要的死因。由于CVD等慢性疾病对健康的威胁越来越大,有必要开展生活方式干预项目以控制这些疾病的危险因素。本研究的目的是评估美国的重要慢病干预项目—HELPS治疗型生活方式改变（TLC）项目对减少CVD危险因素和其他慢性疾病的有效性。方法：140位大学教职工参加为期12周的HELPS TLC项目,干预前后用配对t检验对其体重、BMI、腰围（WC）、6分钟步行距离（6MWD）、空腹血脂和血糖进行测定和比较。结果：干预后6MWD显著增加,总胆固醇（TC）和WC显著下降。对“高危”参与者进一步分析显示：BMI（-1.5±0.5,-3.9%）、TC（- 22.8±4.0,-9.0%）、LDL（- 14.1±4.9,9.3%）和血糖（-6.9±2.2,-6.1%）均显著下降;男性腰围（-4.5±0.8,-10%）显著减小,女性未见显著改变（-1.5±0.5,-4.0%）。此外,体重的变化与TC（r=0.43）、LDL（r=0.35）和血糖（r=0.44）的变化均显著相关。结论：参加12周的生活方式干预项目可以使CVD危险因素减少,特别是在CVD“高危”个体中。HELPS TLC项目的远期效果还待进一步深入研究。  相似文献