Spatial characteristics of professional tennis serves with implications for serving aces: A machine learning approach

This study sought to determine the features of an ideal serve in men’s professional tennis. A total of 25,680 first serves executed by 151 male tennis players during Australian Open competition were classified as either aces or returned into play. Spatiotemporal (impact location, speed, projection angles, landing location and relative player locations) and contextual (score) features of each serve were extracted from Hawk-Eye data and used to construct a classification tree model (with decision rules) that predicted serve outcome. k-means clustering was applied to the landing locations to quantify optimal landing locations for aces. The classification tree revealed that (1) serve directionality, relative to the returner; (2) the ball’s landing proximity to the nearest service box line and (3) serve speed classified aces with an accuracy of 87.02%. Hitting aces appeared more contingent on accuracy than speed, with serves directed >5.88° from the returner and landing <15.27 cm from a service box line most indicative of an ace. k-means clustering revealed four distinct locations (≈0.73 m wide × 2.35 m deep) in the corners of the service box that corresponded to aces. These landing locations provide empirically derived target locations for players to adhere to during practice and competition.     

Comment on Hanasaki Kohei: decolonalization and the assumption of war responsibility

Abstract

The first Asian Lesbian Film and Video Festival, held in Taipei in August 2005, brought forth media art, social activism and cultural exchange on one occasion. It provided a rare opportunity to showcase the experience of Asian lesbians, which is vastly different from the experience of those in Western countries. While there were great similarities in their love experiences among the 36 Asian lesbian shorts selected, they also reflected the differences among the Asian countries in terms of local development of tongzhi culture and community as well as the visibility of tongzhis. Among the Chinese communities, Taiwan was seen to be at the forefront of the development of tongzhi culture, Mainland China was new to the movement, and Hong Kong was somewhere in‐between. Japanese and Korean videos took a critical and reflective attitude towards social regulations and mainstream thoughts, although witty and farcical at times. While the Filipinos show a more tolerant attitude to the Lesbian Gay Bisexual Transgender (LGBT) community, the major oppressive forces on lesbians were poverty, gender inequality and sexual violence. Only one Israeli documentary was shown at the film festival, which focused on lesbians living in the Jewish Orthodox traditions. The film won international acclaim and attracted much public attention to the issue. Films and videos were found to be an effective means to transcend language barriers and cultural differences for a true cross‐cultural exchange among Asian lesbians. During the few days of festival, a ‘queer nation’, not defined by nationalities or languages, but by the pursuit of love expressions, was constructed around The Taipei House.     

Community cartography in health communication: An asset-based mapping approach in four communities in rural Ecuador

Scholars and practitioners are increasingly turning to maps as tools for promoting health and development communication. These maps are often criticized for privileging the interests of the global North and for authorizing (neo)colonial approaches. The authors offer a case of community mapping incorporating asset-based community development that offers an alternative cartography. Drawing on the maps produced by members of four communities in rural Ecuador, the authors articulate how their maps productively use and challenge assumptions about maps. Following this analysis, the authors offer some implications that community-scale maps have for articulating rhetorical alternatives in health and development communication.     

Acute and chronic effect of sodium bicarbonate ingestion on Wingate test performance: a systematic review and meta-analysis

The aim of this study was to perform a systematic review and meta-analysis on the acute and chronic effects of sodium bicarbonate (NaHCO₃) ingestion on Wingate performance. Following a search through PubMed, Scopus and Web of Science, 9 studies were found meeting inclusion criteria (6 acute and 3 chronic). Random-effects meta-analysis of standardized mean difference (SMD) for peak and mean power was performed. Study quality was assessed using the QualSyst. Results of the meta-analysis showed that acute ingestion of NaHCO₃ did not improve Wingate test peak (weighted average effect size Hedges’s g = 0.02, 95%CI: – 0.19 to 0.23, P = 0.87) or mean power (weighted average effect size Hedges’s g = 0.15, 95%CI: ?0.06 to 0.36, P = 0.92). However, chronic ingestion of NaHCO₃ improved Wingate test peak (weighted average effect size Hedges’s g = 1.21, 95%CI: 0.83 to 1.42, P = 0.001) and mean power (weighted average effect size Hedges’s g = 1.26, 95%CI: 0.96 to 1.56, P = 0.001). Quality assessment of selected articles was classified as strong. This meta-analysis provides evidence that chronic, but not acute, ingestion of NaHCO₃ increases both Wingate test peak and mean power.     

Why Olympia matters for modern sport

From the modern scientific perspective, Olympia is a ruin at the far end of a fading sense of history that represents little more than the origins from which sport has continuously evolved. Quantitative measurements show continued increases in human performance, equipment efficiency and funding. But some question this athletic evolution. We worry about qualitative issues, such as virtue, meaning and beauty. The source of this contrast is a difference in values: Olympic vs. Efficiency values. Such values establish an ethos in sporting communities that influences how we behave, explain and even conceptualize our activities. I argue from the perspectives of metaphysics, epistemology, aesthetics, ethics and politics, that Olympic Ethos is needed to balance out the modern Efficiency Ethos, which threatens to dehumanize sport.     

Individualised dietary strategies for Olympic combat sports: Acute weight loss,recovery and competition nutrition

Olympic combat sports separate athletes into weight divisions, in an attempt to reduce size, strength, range and/or leverage disparities between competitors. Official weigh-ins are conducted anywhere from 3 and up to 24?h prior to competition ensuring athletes meet weight requirements (i.e. have ‘made weight’). Fighters commonly aim to compete in weight divisions lower than their day-to-day weight, achieved via chronic and acute manipulations of body mass (BM). Although these manipulations may impair health and absolute performance, their strategic use can improve competitive success. Key considerations are the acute manipulations around weigh-in, which differ in importance, magnitude and methods depending on the requirements of the individual combat sport and the weigh-in regulations. In particular, the time available for recovery following weigh-in/before competition will determine what degree of acute BM loss can be implemented and reversed. Increased exercise and restricted food and fluid intake are undertaken to decrease body water and gut contents reducing BM. When taken to the extreme, severe weight-making practices can be hazardous, and efforts have been made to reduce their prevalence. Indeed some have called for the abolition of these practices altogether. In lieu of adequate strategies to achieve this, and the pragmatic recognition of the likely continuation of these practices as long as regulations allow, this review summarises guidelines for athletes and coaches for manipulating BM and optimising post weigh-in recovery, to achieve better health and performance outcomes across the different Olympic combat sports.     

Now you see,now you don’t … the influence of visual occlusion on racket and ball kinematics in the tennis serve

The serve is considered amongst the most important strokes in tennis. Not surprisingly, the development of a mechanically consistent and proficient serve is paramount. Correspondingly, drills that involve players serving with their eyes closed are thought to promote mechanical consistency. The purpose of this study was therefore to contrast the effect of the removal of visual feedback on ball and racket kinematics in the serve. A 10-camera 500-Hz VICON MX motion analysis system recorded the service actions of eight elite young players as they performed three serves with eyes open and three serves with eyes closed. Removal of vision resulted in considerable differences in both racket and ball kinematics, with players failing to make contact on 16 of 24 serves. Temporally, the preparation phase was significantly shorter with eyes closed. Spatially, the ball was located 6.5 cm further to the right at zenith, and 13 cm higher at impact with eyes closed. These results highlight that the serve is not entirely pre-programmable, and that visual feedback is critical to the spatiotemporal regulation of the serve. In turn, coaches need to be aware of the implications of modifying visual feedback in serve, and ensure that the consequence is congruent with their intent.     

Art and Science in Challenging Needs Assessments: A Case Study

This paper describes a needs assessment project that implemented two distinctive features to address challenges often faced in the needs assessment process. First, a pre‐assessment planning process was developed that successfully educated clients about the analysis process, generated management commitment, identified and prioritized key performance issues, and established an outcomes‐oriented strategic focus for the assessment. Second, to analyze team performance issues, a theory‐to‐practice process was developed that involved the use of discovery‐oriented inquiry within the project context (an inductive approach) with a deductive approach grounded in existing academic research and theory. The complementary and integrated use of these approaches yielded a more comprehensive understanding of the team performance problems, thorough analysis of those problems, and more focused and refined performance improvement recommendations.