Milton Shoiti Misuta

Analysis of the distances covered and technical actions performed by professional tennis players during official matches.

ABSTRACT The purpose of this study was to analyse the physical and technical performances of professional tennis players during official matches. The trajectories of eight players were obtained during matches, using an automatic tracking method. The distances covered and technical performances were analysed for the first and second sets. The athletes covered (mean ± standard deviation) a total of 1702.4 ± 448.2 m in the first set, 1457.6 ± 678.1 m in the second set and 3160.0 ± 880.1 in the entire match. No differences were found between the sets for the physical variables (lateral and forward displacements, distance covered per rally, per game and per set, and the percentage of time spent in each range of velocity). However, the distances covered by the athletes during the rallies in which they were serving (median = 5.2; interquartile range (IQR) = 6.7 m) were statistically smaller than when they were returning (median = 6.2; IQR = 7.7 m). Forehand ground stroke proficiency decreased from the first (mean ± standard deviation: 75.2 ± 4.11%) to the second set (mean ± standard deviation = 65.5 ± 14.3%). In conclusion, tennis players did not present reduced physical performance from the first to the second set.

Technical and tactical soccer players' performance in conceptual small-sided games

El uso de los juegos reducidos conceptuales (JRC) puede ser una interesante metodologia para entrenar a la imprevisibilidad inherente en el juego de futbol. Nuestro objetivo en este estudio fue investigar por videogrametria los principios tecnico-tacticos adoptadas en respuesta a las respectivas reglas de dos JRC distintos (posesion del balon y la progresion a la meta). El estudio incluyo a 24 atletas divididos en equipos de 6 jugadores. Nuestros datos muestran que los principios de organizacion de los JRC crean diferentes situaciones con diferentes grados de dificultad. Es decir, es posible sistematizar el desarrollo de los componentes tecnicos y tacticos de una manera a enfatizar los conceptos adoptados para este estudio en el contexto del juego. Nuestros datos acreditan JRC para el aprendizaje de situaciones tecnicas tacticas que, junto con la preparacion fisica adecuada puede ayudar a producir jugadores capacitados a unir cada vez mas pensamientos y acciones en diferentes situaciones.

Time-motion analysis of goalball players in attacks: differences of the player positions and the throwing techniques

Abstract In this study, we aimed to analyse goalball players time-motion variables (distance covered, time spent, maximum and average velocities) in official goalball match attacks, taking into account the attack phases (preparation and throwing), player position (centres and wings) and throwing techniques (frontal, spin and between the legs). A total of 365 attacks were assessed using a video based method (2D) through manual tracking using the Dvideo system. Inferential non-parametric statistics were applied for comparison of preparation vs. throwing phase, wings vs. centres and, among the throwing techniques, frontal, spin and between the legs. Significant differences were found between the attack preparation versus the throwing phase for all player time-motion variables: distance covered, time spent, maximum player velocity and average player velocity. Wing players performed most of the throws (85%) and covered longer distances than centres (1.65 vs 0.31 m). The between the legs and the spin throwing techniques presented greater values for most of the time-motion variables (distance covered, time spent and maximum player velocity) than did the frontal technique in both attack phases. These findings provide important information regarding players’ movement patterns during goalball matches that can be used to plan more effective training.

Technical Indicators registered as a function of the playing time in Brazilian basketball

Basketball performance analysis using technical indicators dissociated from the moment they occurred in the game seems to no longer respond to emerging issues of the game as it does not identify the periods when a team’s offensive efficiency has increased or decreased. The aim was to characterize and compare the technical indicators in the positive and negative periods and in the whole game of winning and losing teams in men’s professional basketball. Fourteen games of professional men’s teams of the “Novo Basquete Brasil” Championship in the regular 2011/2012 season were filmed and analyzed. The Kolmogorov-Smirnov test was used to verify data normality. The independent T test was used for variables with normal distribution and the Mann-Whitney test for variables that did not present normal distribution, in order to compare teams’ performance. Analysis in the whole game showed that winning teams had significantly higher averages in successful 3-point field goals but in the positive periods, they showed higher averages for successful free throws, successful layups, defensive rebounds and defensive fouls, and in negative periods, losing teams made more defensive and offensive fouls. The teams’ performance in the whole game may not elucidate the determinant indicators for building the difference in the scoreboard. It is suggested that coaches should identify the periods of best and worst teams’ performance in the game and the indicators involved, preparing teams to overcome the negative periods and obtain more positive periods in the game.

Validation of a video-based system for automatic tracking of tennis players

Abstract The purpose of this study was to validate an automatic method for tracking tennis players. The method is based on algorithms for camera calibration, image pre-processing, segmentation, filtering, tracking and computer vision tools. Two digital video cameras (30 Hz) were used to register player movement on a tennis court. The validation of the 2D-reconstructed points was based on the following analysis: intra-operator repeatability (.009 m), inter-operator repeatability (.007 m), relative error (.24% for length and .52% width coordinates) and ICC (.88 consistency and .89 absolute agreement, p < .05). The mean bias and precision were .33 and .15 m, respectively, resulting in an accuracy of .36 m. There were significant linear regressions (p < .05) between positions obtained by the automatic and manual tracking procedures (R2 = .9903 for x-coordinate, R2 = .9952 y-coordinate). The RMS error comparing both methods was .51 m. The percentage of automatic tracking (when the system identified player’s position correctly, without operator intervention) during a simulated match reached 99.98% of the 22,000 frames processed. The distances covered by the two players during a set were 1229.6 and 1083.1 m. In conclusion, the method proposed revealed to be simple, valid and consistent to track tennis players on the court.

Ergonomic and Psychosocial Aspects of Electrical Energy Maintenance Activities on Transmission Lines

In recent years, the electric power sector has undergone considerable changes, contributing to the increase of accidents, mainly in the maintenance activity of transmission lines. The purpose of this project is to identify ergonomic and psychosocial aspects in this activity, through the Ergonomic Work Analysis (EWA), applied to an electric energy concessionaire. This research is underway and the initial results point to the relevance of the organizational aspects associated to the profile of the new workers.

The effect of the maintaining the ball possession on the intensity of games

The use of small-sided games (SSG) for soccer training has increased considerably in recent years. Tactical principles can influence the intensity and the movement of soccer players during training. The aim of this study was to evaluate the influence of maintaining possession of the ball on the intensity and the time of motion characteristics of players during training in games. Eleven athletes of the U-20 category of a professional club in Sao Paulo, Brazil, participated in this study. To check the influence of the tactical principle, we used a game control and an experimental game in three different field dimensions and number of players. The results show that possession of the maintenance rule influences the intensity of the games (p <0.05). However, it is concluded that the rule is fundamental for training through games.