A retrospective investigation on age and gender differences of injuries in DanceSport

In spite of the extensive research on incidence site and type of injury in ballet and modern dancers, limited studies on injury in DanceSport have been reported. Therefore, this study determined retrospectively (within last 12 months) incidence, severity, site and type of injury, between gender and age-class in DanceSport. Participants were 97 international sport-dancers (female, 41; male, 56). Sixty-six (69%) dancers reported 96 injuries (1.00 (range = 4)) injuries per dancer) and an injury incidence of 1.7 (range = 14) per 1000 h. Females revealed significantly higher median injury incidence (females, 2.6 (range = 14); males, 1.9 (range = 9), p 0.05) than males. A total of 61.5% of all injuries recorded were traumatic with a significant gender difference (Wald chi-square = 11.616, df = 1, p 0.01). Injury severity was 3 (range 240) days with an interaction effect between gender and age-class (Wald chi-square = 251.374, df = 3, p 0.001). Meanwhile, 72.3% of the dancers reported not including sport specific exercises besides dancing. These findings show gender and age-class differences in injury incidence, type and severity. Therefore, to reduce the likelihood of injuries, the implementation of supplemental DanceSport specific exercises that also considers the gender and age-class anatomical, functional, and choreographic demand differences in the training program should be recognized

Photo-oxidative tuning of individual and coupled GaAs photonic crystal cavities

We demonstrate a new photo-induced oxidation technique for tuning GaAs photonic crystal cavities using a $390~\mathrm{nm}$ pulsed laser with an average power of $10~\mathrm{\mu W}$. The laser oxidizes a small $\left(\sim 500~\mathrm{nm}\right)$ diameter spot, reducing the local index of refraction and blueshifting the cavity. The tuning progress can be actively monitored in real time. We also demonstrate tuning an individual cavity within a pair of proximity-coupled cavities, showing that this method can be used to correct undesired frequency shifts caused by fabrication imperfections in cavity arrays.Comment: 4 pages, 3 figure

Inverse design and implementation of a wavelength demultiplexing grating coupler

Nanophotonics has emerged as a powerful tool for manipulating light on chips. Almost all of today's devices, however, have been designed using slow and ineffective brute-force search methods, leading in many cases to limited device performance. In this article, we provide a complete demonstration of our recently proposed inverse design technique, wherein the user specifies design constraints in the form of target fields rather than a dielectric constant profile, and in particular we use this method to demonstrate a new demultiplexing grating. The novel grating, which has not been developed using conventional techniques, accepts a vertical-incident Gaussian beam from a free-space and separates O-band $(1300\mathrm{nm})$ and C-band $(1550\mathrm{nm})$ light into separate waveguides. This inverse design concept is simple and extendable to a broad class of highly compact devices including frequency splitters, mode converters, and spatial mode multiplexers.Comment: 17 pages, 4 figures, 1 table. A supplementary section describing the inverse-design algorithm in detail has been added, in addition to minor corrections and updated reference

Using a situation awareness approach to determine decision-making behaviour in squash

Situation awareness (SA) refers to the awareness of all relevant sources of information, an ability to synthesise this information using domain knowledge gained from past experiences and the ability to physically respond to a situation. Expert-novice differences have been widely reported in decision-making in complex situations although determining the small differences in expert behaviour are more elusive. This study considered how expert squash players use SA to decide on what shot to play. Matches at the 2010 (n = 14) and 2011 (n = 27) Rowe British Grand Prix were recorded and processed using Tracker software. Shot type, ball location, players' positions on court and movement parameters between the time an opponent played a shot prior to the player's shot to the time of the opponent's following shot were captured 25 times per second. Six SA clusters were named to relate to the outcome of a shot ranging from a defensive shot played under pressure to create time to an attempted winner played under no pressure with the opponent out of position. This new methodology found fine-grained SA differences in expert behaviour, even for the same shot type played from the same court area, beyond the usual expert-novice differences

Determining unstable game states to aid the identification of perturbations in football

Alternative approaches to the reductionist method for analysing football are needed to better understand factors typically not considered, for example off the ball runs by teammates. The dynamical systems approach, where the complex relationships between players is emphasised, predicts that goal scoring opportunities are preceded by instability in the balance between the two teams’ behaviours. The aim was to create operational definitions for determining unstable game states to facilitate the identification of perturbations, that is the causes of instability. Validity tests involving four English Premier League (EPL) football coaches and two performance analysts and subsequent reliability tests established five unstable game states; penalty box possession, counter attack, ratio of attacking to defending players, successful cross and successful shot. Eighteen EPL matches were analysed to present exemplar statistics for three teams of different standard (based on final league position) suggesting that teams create unstable situations differently, likely due to individual player characteristics, with home advantage and opposition strength effects, suggesting this may be a component of what constitutes a performance indicator for a team. Future studies need to consider individual player actions that create instability as well as provide objective measures that substantiate findings

Using a situation awareness approach to identify differences in the performance profiles of the world’s top two squash players and their opponents

Purpose The pressure exerted on a squash player is a consequence of the quality of a shot coupled with the ability of the player to return the ball, namely, the coupling of the two players’ situation awareness (SA) abilities. SA refers to an awareness of all relevant sources of information, the ability to synthesize this information using domain knowledge and the ability to physically respond to a situation. Methods Matches involving the two best players in the world (n = 9) at the 2011 Rowe British Grand Prix, held in Manchester, United Kingdom were recorded and processed using Tracker software. Shot type, ball location, players’ positions on court and movement parameters between the time an opponent played a shot prior to the player’s shot to the time of the opponent’s following shot were captured 25 times per second. All shots (excluding serves and rally ending shots) produced five main SA clusters, similar to those presented by Murray et al. (2018), except a greater proportion of shots were categorized in the greater pressure clusters and less in the lower pressure ones. Results Individual matches were presented using cluster performance profile infographics which demonstrated how individual player’s performance profiles differed between matches. Conclusion It is suggested that it is the coupling, of the two player’s behaviors, that makes the examination of tactics so challenging. This inherently means that performance profiles vary in subtle ways, making consistent profiles that are independent of the opponent very unlikely for elite players. This approach should be further modified to determine within match changes in performance

Does SAQ training improve the speed and flexibility of young soccer players? A randomized controlled trial

The aim of this study was to determine the effects of a 12-week speed, agility and quickness (SAQ) training program on speed and flexibility in young soccer players. One hundred and thirty-two soccer players were randomly assigned to experimental (EG; n = 66, Mean±SD: age: 18.5 ± 0.4 years (range 17-19 years); body mass: 71.30 ± 5.93 kg; stature: 177.2 ± 6.5 cm) and control groups (CG; n = 66, Mean±SD: age: 18.6 ± 0.6 years (range 17-19 years); body mass: 70.63 ± 4.87 kg; stature: 175.9 ± 5.7 cm). The experimental group performed SAQ training whilst the control group undertook straight-line sprint training matched for volume and duration. Sprint performance was assessed using 5 m and 10 m sprints and a further test including maximal speed, a 20 m sprint. Flexibility was assessed using sit and reach, V-sit and reach, leg lift from supine position and lateral leg lift while lying on the side tests. Sprints over 5, 10 and 20 m did not differ between groups at baseline, but by week 12, the 5 m sprint had significantly improved (P 0.05) for all flexibility tests were found between experimental and control group at baseline and after the training programmes. Consequently SAQ training was found to be an effective way of improving sprint time for short distances over 5 and 10 m but not over 20 m (where maximum speed was achieved) or flexibility. These results indicate that SAQ training may be more effective for improving sprint performance for some soccer players but more research is required to determine ideal training methods for improving acceleration and flexibility in young soccer players

The attacking process in football: a taxonomy for classifying how teams create goal scoring opportunities using a case study of Crystal Palace FC

Purpose: Whilst some studies have comprehensively described the different features associated with the attacking process in football they have not produced a methodology of practical use for performance enhancement. This study presents a framework of comprehensive and meaningful metrics to objectively describe the attacking process so that useful performance profiles can be produced. Methods: The attacking process was categorized into three independent situations, no advantage (stable), advantage, and unstable (potential goal scoring opportunity) situations. Operational definitions for each situation enhanced their reliability and validity. English Premier League football matches (n = 38) played by Crystal Palace Football Club in the 2017/2018 season were analyzed as an exemplar. Results: Crystal Palace FC created a median of 53.5 advantage situations (IQR = 16.8) and 23 unstable situations (IQR = 8.8) per match. They frequently utilized wide areas (Median = 21.5, IQR = 9.8) to progress, but only 26.6% resulted in unstable situations (Median = 6.0, IQR = 3.8), the lowest rate compared to the other advantage situations. Conclusion: This classification framework, when used with contextual factors in a multi-factorial manner, including individual player contributions, will provide practically useful information for applied practice. This approach will help close the so called theory-practice gap and enable academic rigor to inform practical problems