Volleyball features a unique rule known as rotation, and while previous studies have quantified its importance, they often fail to consider the serving phase, that is, whether a team has the right to serve. In this study, we used machine learning predictions to quantitatively analyze the importance of rotation while accounting for the serving phase. We collected data using Volley Station from 180 matches in the 2023–24 V.LEAGUE DIVISION 1 MEN's League (V1 Men) and 82 matches in the 2022–23 V.LEAGUE DIVISION 2 MEN's League (V2 Men). A machine learning-based win-loss prediction model was employed for the analysis. The explanatory variables were the scoring percentages in 12 distinct situations, each combining different phases and rotations. The outcome variable was the match result, coded as 1 for a win and 0 for a loss. We utilized three types of predictive models, logistic regression, linear discriminant analysis, and Light GBM, to calculate prediction accuracy and assess the importance of serving phase and rotation. Our analysis revealed that in the V1 Men's League, break phase rotations B-S6 and B-S5 were especially important. In these rotations, the opposite hitters were in front-row positions, and differences in blocking ability were pronounced. Conversely, in the V2 Men's League, side-out phase rotations S-S6, S-S5, and S-S2 were particularly significant. In these rotations, the ability to execute reception attacks showed a marked difference between winning and losing teams.

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The purpose of this study was to quantify the changes in movement and performance of general students during their practice of mastering the float serve, and to obtain basic information on effective coaching methods. The subjects were 14 college students with no experience in volleyball competition. The coaching and practice of serves and the filming of the trials were conducted a total of 14 times once a week. The serves were recorded from behind and to the right, and each subject performed a total of 4 attempts. The subjects were verbally instructed to "toss the ball high", "touch the back of the head with the right hand just before hitting the ball", and "hit the ball with the left foot forward". The items analyzed were evaluation, initial ball velocity, ball hitting angle, impact point height, front and back position of the ball, and wrist height. As a result, the front and back position of the ball changed significantly backward to 4.9±7.6cm in the fourth experiment, and the most backward change was in the ninth experiment, where the impact point changed to -4.4±6.4cm behind the top of the head. A very high correlation (r=0.93) was observed between the forward distance and the elevation angle. The reason for the forward distance changing backward is thought to be the strong influence of the verbal instruction to pull the hitting arm largely upward and backward. Furthermore, since a high correlation was observed between the ball hitting angle and the front and back position of the ball, it seems necessary to move the point of catching the ball slightly behind the top of the head.in order to increase the ball hitting angle of the ball. From the above, it is inferred that verbal instruction to hit the ball behind the head are one of the effective methods for improving serving technique when teaching float serves in volleyball instructions for general students.

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In this study, we investigated the factors related to the differences in abilities of female volleyball players whose performance changed according to different matches in nine-player volleyball. The participants were divided into two groups: one group included players who performed better in training matches than in official matches (DG: declined group), and the other group included players who performed better in official matches than in training matches (EG: enhanced group). A total of nine female volleyball players (24.9±1.36 years) from the V9 Champ League 2023 participated in this study. The following factors were compared between the groups: years of experience in nine-player volleyball and six-player volleyball, height, body-fat percentage, muscle quality, reaction time, and design fluency test (DFT). DFT, a test that measures executive function, comprises three tests (basic, filter, and switch tests) and participants were asked to make variations to connect five dots with four lines in 60 seconds. Superior executive function may help individuals adapt to changes in situations and inhibit impulsive actions. The scores of DFT used in this analysis were DFT-T (the total number of correct answers across all three tests of DFT), DFT-B&F (the total number of correct answers in the basic and filter tests of DFT), and DFT-S (the total number of mistakes, with the same answers being repeated considered as mistakes). Our results showed that body-fat percentage was significantly lower in the EG than in the DG. In addition, although the difference was not significant, the effect size in DFT-B&F was large, with a higher score in the EG. These results revealed that participants who performed better in official matches than in training matches had better executive function; the lower levels of body-fat percentage also helped the players demonstrate high performance given their superior executive function.

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In this study we investigated the incidence of lumber sports injuries and disorders in high school male volleyball players. The subjects were 95 high school male volleyball players from the upper level of the district. The survey period was one year from June 2022 to June 2023. The survey was conducted using a paper check sheet, and coaches and players on each team were asked to record information about training and participation in games on a daily basis, as well as records of sports injuries and injuries. Based on the data obtained, the incidence of sports injuries and injuries per 1,000 Player Hours (PH) and 1,000 Athlete Exposure (AE) was calculated. The number of hours of participation in the game was 50,777.0 hours and the number of EA was 16,211 in one year. There were a total of 22 sports injuries and injuries occurring during volleyball practice, with an incidence of 0.41/1,000 PH and 1.3/1,000 AE. Of these, 19 occurred during training and 3 occurred during matches. The most frequent location was the ankle (6 cases), followed by the lumbar region (5 cases). All sports injuries and injuries to the lumbar region occurred during practice, with incidence rates of 0.10/1,000 PH and 0.31/1,000 AE, with three non-temporary losses and two severe hourly losses. In addition, 4 out of 5 cases that occurred in the lumbar region were slow-onset due to repeated loads. The incidence of sports injuries and lower back injuries among high school male volleyball players was second only to ankle trauma, suggesting that most of them were caused by injuries caused by repeated loads. These results suggest that low back disorders in high school volleyball players can be prevented by learning correct form and performing proper basic training, regardless of the level of competition.

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In this study, the physical characteristics of the study was to obtain knowledge on the offensive and defensive abilities required of outside hitter and on the select of players in volleyball by clarifying the factors related to the physical characteristics of players, performance data on offense and defense, and winning and losing.
The results showed that there was a clear improvement in the serve receive return rate and the maximum jump reach among in terms of individual player performance between 2018/19 and 2023/24. However, there was a　correlation with the attack success rate in terms of winning sets in matches. From this, it became clear that while the tendency of outside hitter players in recent university top leagues is to strive to improve their serve receive skills and physical characteristics, in terms of match-related performance, the attack success rate has a large impact on the match results. The results suggest that it is important to consider what to prioritize as a team situation based on these indicators when selecting players.

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