A shot taxonomy in the era of tracking data in professional tennis

Shots are an essential part of the language of tennis yet little is known about the distinct types of shots in the professional game. In this study, we build a taxonomy of shots for elite tennis players using tracking data from multiple years of men’s and women’s matches at the Australian Open. Our taxonomy is constructed using model-based multi-stage functional data clustering, an unsupervised machine learning approach. Among 270,023 men’s and 178,136 women’s shots, we found 13 distinct types of serves to both the Ad and Deuce court for male players and 17 and 15 types to the Ad and Deuce for female players. More variety was found among serve returns and rally shots compared to the serve; with less variety on the backhand than forehand. There was also more overlap in the physical characteristics of groundstroke shots between male and female players than on serve. Shot type was strongly associated with winning points and shots in the highest speed and lowest net clearance categories tended to be the most effective. This data-driven dictionary of shots provides a framework for analysis of elite player performance, characterizing playing style, and designing more representative practice.     

A Mathematical Model for Evaluating Scoring Systems with Specific Reference to Tennis

Abstract

The purpose of this investigation was twofold: (a) to examine the feasibility of using mathematical probability models to evaluate scoring systems; and (b) to actually examine, by use of the model, the relative merits of various tennis scoring systems. The hypothesized model was a Markov chain with stationary transition probabilities, the total chain being divided into an initial process and a random walk. By assessing a constant probability p that player A would win a point against his opponent B, and applying probability theory to the initial Markov process and the random walks, the probability that A would win the match was calculated. This was done for each of the various scoring systems. Under the assumption that the “best” player was the one with the highest probability of winning a point, the scoring method which would most frequently result in this best player being declared the winner was ascertained. Further analysis yielded the expected number of points that would be played in a match, thus giving an indication of the efficiency of the scoring system. Data from the 1967 professional tennis tour for 14 matches (350 games) between Rod Laver and Andres Gimeno were applied to the model and yielded results agreeing very closely with the hypothesized outcomes.     

Logic of Questionable Density

Abstract

The probability of winning a game of tennis from scratch in terms of the probability of winning an individual point has been well documented. However, once the game is underway this probability rapidly changes. This paper presents formulas for the conditional probabilities of a player winning a game from any scoreline. Each point is ranked in order of importance with regard to winning the game. A number of interesting and surprising features arise and an area of further research is suggested.     

A Tennis Forehand-Backhand Drive Skill Test Which Measures Ball Control and Stroke Firmness

Abstract

A tennis skill test for use in quantifying achievement in the forehand and backhand drive strokes was developed and then validated using 76 college women enrolled in beginning tennis classes. The test consisted of returning balls pitched by a pneumatic ball machine into target areas drawn in chalk on a regulation tennis court. Speed of the subjects' shots was assessed by measuring accumulated time in flight for rounds of 10 trials using a stopwatch. A time factor was then employed to correct the target value total for the trials to adjust for ball speed, thus rewarding the more skilled player who could stroke the ball more firmly while still retaining control. The test-retest reliability of the test was found to be .84, while the validity of the test, using judges' ratings as a criterion, was .83. It was concluded that the test was a valid and reliable test of skill which was closely related to the actual game situation. Percentile norms were developed on a limited number of subjects.     

中外优秀女子网球运动员竞技年龄特征比较分析

采用文献资料法、数理统计法、逻辑归纳法等研究方法对中外20名优秀女子网球运动员的竞技年龄特征进行比较分析,发现:中外优秀女子网球运动员在启蒙训练年龄上的差异并不显著;但是外国优秀女子网球运动员转为职业选手的年龄较早,所以其成为职业选手的年限也较长。中国优秀女子网球运动员之间的现役年龄的分布较为离散,中国十名优秀女子网球运动员的现役年龄差异大于国外十名优秀女子网球运动员的现役年龄差异;并且中国优秀女子网球运动员达到最高竞技水平的年龄比国外优秀女子网球运动员达到最高竞技水平的年龄晚。     

国内专业网球运动员体能瓶颈突破的研究及建议

体能瓶颈的出现是国内专业网球运动员向世界职业网坛迈进的一大门槛。本文采用录像统计法、数理统计法、文献资料,对因体能原因出现伤病的国内优秀网球运动员进行康复跟踪、设计训练、监督训练、定时测试,在进行康复的同时利用新的体能理念进行训练,完成体能突破瓶颈的任务。     

Scaling Constraints in Junior Tennis: The Influence of Net Height on Skilled Players’ Match-Play Performance

Purpose: The net height in tennis (0.91 m) is approximately 50% of a professional tennis player’s height. Children are also expected to play with this net height, even though it is approximately 70% of the average 10-year-old’s height. This study examined the immediate effect of lowering net height on the performance characteristics of skilled junior tennis players aged 10 years and younger. Method: Sixteen players were matched in 8 pairs of even tennis ability and same sex. Each pair played 25-min singles matches in 4 conditions that varied in net height (0.91 m, 0.78 m, 0.65 m, and 0.52 m). Match-play characteristics were analyzed via video replay. Results: Results showed that lowering the net height to 0.65 m and 0.52 m led to players adopting a more attacking style of play, as evidenced by a significant increase in the number of winners without a commensurate increase in errors and more shots struck inside the baseline. Lower nets also led to a greater percentage of successful first serves. The lowest net (0.52 m), however, reduced rally length significantly and therefore decreased hitting opportunities. Conclusion: These results offer support for equipment scaling to enhance match-play performance for skilled junior tennis players. We propose that current net height recommendations for junior tennis should be revised.     

Expectancy effects in tennis: The impact of opponents' pre-match non-verbal behaviour on male tennis players

Abstract

In this study, we examined the impact of a male opponent's pre-match body language and clothing (general vs. sports-specific) on how his performances were judged by an observer. Forty male tennis players viewed videos of a male target tennis player warming up and then observed playing footage of the target. Each participant viewed the target player warming up displaying one of four combinations of body language and clothing (positive body language/tennis-specific clothing; positive body language/general sportswear; negative body language/tennis-specific clothing; negative body language/general sportswear). Participants rated the performance of the tennis player and gave their perceptions of the likely outcome of a tennis match with the target player. Analyses of variance indicated that clothing and body language had an interactive effect on both outcome expectations and ratings of performance. The findings support the contention that the initial impressions athletes form of their opponents can influence the way in which they judge the performances of opponents and their perceived likelihood of success against the same opponents.     

Dynamics of players’ relative positioning during baseline rallies in tennis

Abstract

This study analysed how the relative positioning of players on court influenced patterns of interpersonal coordination in baseline rallies in tennis. We developed a model (PA index) that assigns a weight to the position of each player on court and determines a positional advantage, based on the relative proportionality between the lateral and longitudinal displacement values during rallies. To test the model, data from 27 randomly-selected baseline rallies from three ATP World Tour matches (professional tennis players' tournaments organized by Association of Tennis Professionals) on clay were analysed. Results revealed that the PA index of players on court described their interpersonal coordination dynamics during baseline rallies. It also identified the emergence of rally breaks in the interpersonal coordination patterns of competing dyads that led to a point being scored. Data suggest that positional advantage data may assist coaches in the design of training tasks to enhance players' court coverage and performance during competitive interactions, acting as a valuable tool for performance analysis in tennis.     

乒乓球运动节奏之功效

节奏是技术动作在时间、空间、力量等方面相互配合的一种综合表现,并存在于一切运动之中。运动节奏的合理与否、精确与否对掌握运动技术和提高运动技术水平以及实战效果均起着非常重要的作用。乒乓球每项技术本身以及与其他技术之间均包含着节奏和节奏变化。因此,正确的节奏对提高乒乓球技术、战术、比赛水平具有非常重要的意义。乒乓球比赛不仅仅需要运动员综合实力强,更要求教练员能够根据实战情况,指导运动员正确而巧妙运用节奏谋略,充分利用节奏变化,这样才能最终赢得比赛。     

Expert-level classification of ventilatory thresholds from cardiopulmonary exercising test data with recurrent neural networks

Abstract

First and second ventilatory thresholds (VT₁ and VT₂) represent the boundaries of the moderate-heavy and heavy-severe exercise intensity. Currently, VTs are primarily detected visually from cardiopulmonary exercise test (CPET) data, beginning with an initial data screening followed by data processing and statistical analysis. Automated VT detection is a challenging task owing to the high signal to noise ratio typical of CPET data. Recurrent neural networks describe a machine learning form of Artificial Intelligence that can be used to uncover complex non-linear relationships between input and output variables. Here we proposed detection of VTs using a single neural network classifier, trained with a database of 228 laboratory CPET data. We tested the neural network performance against the judgement of 7 couples of board-certified exercise-physiologists on 25 CPET tests. The neural network achieved expert-level performances across the tasks (mean absolute error was 9.5% (r?=?0.79) and 4.2% (r?=?0.94) for VT₁ and VT₂, respectively). Estimation errors are compatible with the typical error of the current gold standard visual methodology. The neural network demonstrated VT detecting and exercise intensity level classifying at a high competence level. Neural networks could potentially be embedded in CPET hardware/software to extend the reach of exercise physiologists beyond their laboratories.     

Alterations in Body Size and Composition Consequent to Astro-Trimmer and Slim-Skins Training Programs

Tennis is an activity requiring both endurance and anaerobic components, which could have immunosuppressive effects postexercise.

Purpose

The purpose of this investigation was to determine the effect of a simulated tennis match on apoptotic and migratory markers on lymphocyte subsets.

Method

Male high school (n = 5) and college (n = 3) tennis players (M _age = 18.9 ± 3.3 years) completed 10 sets of a tennis protocol including serves, forehand strokes, and backhand groundstrokes with 1-min rest periods between sets. Apoptosis antigen 1 receptor (CD95) and chemokine receptor fractalkine (CX₃CR1) expression was analyzed on helper T lymphocytes (CD4+), cytotoxic T lymphocytes (CD8+), and B lymphocytes (CD19+) twice, at resting baseline and immediately after all 10 sets of the tennis protocol.

Results

An increase was observed in each lymphocyte subtype (p < .02, effect size = .41), and comparison of absolute changes revealed increases in CD4+/CD95+, CD8+/CD95+, and CD8+/CX₃CR1 lymphocytes following the tennis protocol (p < .01, effect size = .43), but not in CD19+ cells.

Conclusions

A simulated tennis match has adequate intensity to induce immune modulations in terms of increased cell death and cellular migration in T lymphocyte subsets. Lymphocytopenia following tennis play is influenced by both apoptotic and migratory mechanisms.     

‘Doing it for Dot’: exploring active ageing sport tourism experiences through the medium of creative analytical practice

ABSTRACT

This is a true story about the active sport tourists encountered at the 17th World Veterans Championships (WVC 2014), with a particular focus on the movements and memories of the world's oldest international table tennis player. Through the employment of creative analytical practice and, more specifically, creative non-fiction, I offer an (auto)ethnographical narrative designed to target your sociological imagination, engendering a deeper, personally applicable, appreciation towards the consumption and production of active sport tourism. A couple of overlapping evocative vignettes offer a candid insight into how new awareness, attraction, attachment and allegiance have been created from my personal involvement and social interaction with over 200 active ageing athletes, including an inspiring Australian centenarian named Dorothy (Dot) de Low. By sharing my story, I hope to encourage others to stop hiding in the shadows, embrace their subjectivity and share their lived experiences of active sport tourism engagement.     

Where to go: Computational and visual what-if analyses in soccer

ABSTRACT

To prepare their teams for upcoming matches, analysts in professional soccer watch and manually annotate up to three matches a day. When annotating matches, domain experts try to identify and improve suboptimal movements based on intuition and professional experience. The high amount of matches needing to be analysed manually result in a tedious and time-consuming process, and results may be subjective. We propose an automatic approach for the realisation of effective region-based what-if analyses in soccer. Our system covers the automatic detection of region-based faulty movement behaviour, as well as the automatic suggestion of possible improved alternative movements. As we show, our approach effectively supports analysts and coaches investigating matches by speeding up previously time-consuming work. We enable domain experts to include their domain knowledge in the analysis process by allowing to interactively adjust suggested improved movement, as well as its implications on region control. We demonstrate the usefulness of our proposed approach via an expert study with three invited domain experts, one being head coach from the first Austrian soccer league. As our results show that experts most often agree with the suggested player movement (83%), our proposed approach enhances the analytical capabilities in soccer and supports a more efficient analysis.     

Relative Strenuousness of Selected Sports as Performed by Women

Abstract

Women participants in archery, badminton, basketball, bowling, golf, hockey, Softball, tennis, and volleyball were tested to determine the relative strenuousness of these sports. The subjects' heart beats were telemetered during participation in each sport, and estimates of their ventilation and oxygen uptake for each activity were determined from data collected in the laboratory.

Mean heart rates, oxygen uptake and VO₂ per kilogram of body weight were calculated for each subject in each sport. Comparisons were made to determine which activities demanded the greatest energy expenditure.

Heart rates ranging from a mean of 85 beats/min. in bowling to a mean of 185 beats/min. for the roving player in basketball were recorded. The energy expenditure of the roving player in basketball was similar to that of the center halfback in hockey; these two positions required a significantly greater O₂ uptake than the positions tested in all other sports. Play in these positions was classified as heavy activity.

The non-roving positions of forward and guard in basketball, badminton, tennis, Softball (pitcher), and volleyball were rated as moderate activity. Golf, archery, and bowling were categorized as light activity in terms of energy expenditure.     

The Influence of Tennis Racket Flexibility and String Tension on Rebound Velocity Following a Dynamic Impact

Abstract

The effects of string tension and longitudinal racket flexibility on post-impact ball velocity were investigated in tennis. Six wooden rackets, two with flexible shafts, two with medium and two with stiff shafts were strung with synthetic gut at tensions of 245N (55 lb), 289N (65 lb) and 334N (75 lb).

A pneumatically driven racket-arm was triggered by a stimulus from a photo-electric cell positioned at the exit nozzle of a ball machine so that impact occurred with the racket perpendicular to the path of the ball. New tennis balls were fired to impact each racket at the geometric center of the strings and 5 cm above the geometric center. The average horizontal velocity of the ball, both before and after impact, was determined using stroboscope photography.

A significant interaction between racket stiffness and string tension was recorded for an inward ball velocity of 22.7 m/s and a racket velocity of approximately 6.8 m/s. String tension had no significant influence on rebound velocity for a stiff racket following impact with a moving racket. Medium and flexible rackets produced the highest coefficients of restitution when strung at 245N (55 lb) compared to 289N (65 lb) and 334N (75 lb).     

Morphology of the deltoid muscles in elite tennis players

Abstract

The aim of this study was to examine the deltoid muscle properties of the dominant and non-dominant arm of Greek professional male tennis players. Eight male tennis players (mean age 22.0 years, s = 3.2) were subjected to biopsy of the deltoid muscle of both arms. Adenosine triphosphate (ATPase) histochemistry and myosin heavy chain (MHC) composition were performed on the samples with homogenate electrophoresis. No significant differences were observed in the percentage of types I, IIa, IIab, and IIb muscle fibres between the deltoid muscles of the two arms. Types I, IIa, and IIx muscle fibres of the dominant and non-dominant deltoid muscles did not differ significantly for MHC isoform composition. Type IIab muscle fibres showed a similar cross-sectional area (CSA) percentage distribution between the two arms. The CSA percentage for types I, IIa, and IIb muscle fibers did not differ significantly between the dominant and the non-dominant arm. We conclude therefore that regular tennis training probably does not lead to any significant changes in the muscle fibre types of the dominant and non-dominant arms of elite tennis players.     

Physiological demands of match-play in elite tennis: A case study

Abstract

The physiological and perceptual demands together with match notation of a four-set tennis match were studied in two elite professional players during the preparation for the 2008 Davis Cup. The design of this case report is unique in that it is the first to describe the demands of prolonged match-play (197 min) over four sets in ecologically valid conditions. The variables measured before and after each set included blood lactate and glucose concentrations, body mass, and perception of effort. Stroke count for each rally and heart rate were recorded during each set while salivary cortisol concentration was determined before and after the match. The rally length decreased as the match progressed. The results showed significant physiological stress, with each player losing greater than 2.5% of body mass (as fluid) and having elevated salivary cortisol concentrations after the match. Heart rate and perception of effort were also increased following each set indicating increasing stress. However, blood lactate decreased following the fourth set while blood glucose was maintained. The results also suggest that elite players may adjust work rates or tactics to cope with the increased perception of effort. This report shows that four sets of tennis are associated with increasing stress and fatigue.     

The influence of tennis court surfaces on player perceptions and biomechanical response

This study aimed to examine player perceptions and biomechanical responses to tennis surfaces and to evaluate the influence of prior clay court experience. Two groups with different clay experiences (experience group, n = 5 and low-experience group, n = 5) performed a 180° turning movement. Three-dimensional ankle and knee movements (50 Hz), plantar pressure of the turning step (100 Hz) and perception data (visual analogue scale questionnaire) were collected for two tennis courts (acrylic and clay). Greater initial knee flexion (acrylic 20. 8 ± 11.2° and clay 32.5 ± 9.4°) and a more upright position were reported on the clay compared to the acrylic court (P < 0.05). This suggests adaptations to increase player stability on clay. Greater hallux pressures and lower midfoot pressures were observed on the clay court, allowing for sliding whilst providing grip at the forefoot. Players with prior clay court experience exhibited later peak knee flexion compared to those with low experience. All participants perceived the differences in surface properties between courts and thus responded appropriately to these differences. The level of previous clay court experience did not influence players’ perceptions of the surfaces; however, those with greater clay court experience may reduce injury risk as a result of reduced loading through later peak knee flexion.