A Longitudinal Study on the Evolution of the Four Main Football Leagues Using Artificial Intelligence: Analysis of the Differences in English Premier League Teams.

Purpose: The aim of this study was to analyze the evolution of the four most important leagues and to identify if there are differences between the English Premier League and the rest of the European leagues. Methods: Each team was characterized according to a set of 52 variables including offensive, defensive, and buildup 10 variables that were computed from OPTA's on-ball event records of the matches for main national leagues between the 2014 and 2018 seasons. To test the evolution of leagues, the t-SNE dimensionality reduction technique was used. To better understand the differences between leagues and teams, the most discriminating variables were obtained as a set of rules discovered by RIPPER, a machine learning algorithm. Results: The evolution of playing styles has meant that teams in the major European leagues seem to 15 be approaching homogeneity of technical-tactical behavior. Despite this, a distinction can be seen between the English teams concerning the rest of the teams in the other leagues, determined by fewer free kicks, fewer long passes but more vertical, more errors in ball control but greater success in dribbling. Conclusions: These results provide important knowledge and practical applications because of the study of the different variables and performance indicators among the best football championships.

Promoting Physical Activity Habits after Completing Secondary School: Does the Age Matter?

Physical inactivity is one of the most important problems in our society, especially during adolescence. During this stage of schooling, students practice physical activity in physical education classes, but after they finish school, many of them stop practicing it. This research aims to determine which variables predict the intention to practice physical activity after finishing secondary school and to discover the effect that age during adolescence has on these predictive variables. A questionnaire was administered to a sample of secondary school students. The results show that physical exercise identity influences the three antecedents of this theory, while the attitude towards the behaviour (ß = 0.13; p < 0.05), perceived behavioural control (ß = 0.46; p < 0.05), and physical self-concept (ß = 0.41; p < 0.05), have a statistically significant influence on the intention to be physically active. Moreover, when the age is lower, is more important to develop a positive perceived behavioural control and physical exercise identity. Moreover, for younger male adolescents instead of the physical exercise itself, identity seems more important in developing a positive attitude towards behaviour. Likewise, in young female adolescents a low level of support from their close environment (subjective norm) leads to dropping out. The research concludes with the importance of including these variables in physical education classes to promote physical activity practice after completion of secondary school. Some practical implications are presented.

Anthropometric, Physiological, and Psychological Variables That Determine the Elite Pistol Performance of Women.

Shooting is a high-precision sport that depends on many factors to achieve high performance levels. The main objective of this study was to analyze the differences in anthropometric, physiological, and psychological variables by sport level in women air-pistol shooters. Fifteen female pistol shooters, including seven elite national shooters of Iran and eight non-elite shooters, participated in this study. Analyzed variables were grouped into three sections: anthropometric, physiological, and psychological. Anthropometric variables included: height, weight, body mass index, length of leg, arm span, and proportions between variables. Physiological tests include resting heart rate, static and dynamic balance, flexibility, and upper body strength. Additionally, psychological questionnaires of SMS-6 sport motivation, TSCI trait sport-confidence and SSCI state sport-confidence, ACSI-28 athletic coping skills, and SAS sport anxiety scale were used. The Shapiro-Wilks test and independent t-test were used to analyze the data. Effect size and test reliability were calculated using Cohen's d and Cronbach's alpha, respectively. Our results showed that elite shooters have higher values of dynamic balance (Y-test), upper body strength (sit-ups), and intrinsic motivation, and lower resting heart rate than non-elite. However, no differences were found in the anthropometric variables, nor in anxiety or coping skills. We conclude that physiological and psychological workouts should be included in the shooters' training programs to improve their performance.

Correction: García-Aliaga et al. Comparative Analysis of Soccer Performance Intensity of the Pre-Post-Lockdown COVID-19 in LaLiga™. Int. J. Environ. Res. Public Health 2021, 18, 3685.

The authors wish to make the following corrections to this paper [...].

Optoelectronic analysis of technical factors and performance of elite-level air pistol shooting.

Technical elements are related to shooting performance; however, the importance of each factor regarding performance, especially in elite-level pistol shooters, remains controversial. The objective of this study was to determine the technical factors that influence pistol performance. One elite-level shooter was analysed during the season before the Olympic classification European championship through a total of six competitions (n = 360 shots). Aiming point trajectories were measured with the SCATT optoelectronic system. Variables were classified into six categories: performance; aiming time; stability of hold; aiming accuracy; cleanness of triggering and shooting delta. Principal component analysis, multiple regressions, Pearson correlations and ANOVAs were used to analyse the data. The results showed that five components (aiming time, stability of hold, aiming accuracy, cleanness of triggering and shooting delta) determined a total of 79.68% of the shooting variance. Specifically, aiming accuracy and cleanness of triggering explained up to 25% of the shooting score, with cleanness of triggering serving as the determining factor. Correlations were found among the performance and stability of hold, aiming accuracy, cleanness of triggering and shooting delta. Last, significant differences were found among 8-score, 9-score and 10-score shots. We conclude that while aiming accuracy seems to be related to the performance, cleanness of triggering could be the most critical technical element; furthermore, while stability of hold does not seem to be a determining factor of the score, it could be a general prerequisite to achieve high levels of performance in elite-level air pistol shooters.

Comparative Analysis of Soccer Performance Intensity of the Pre-Post-Lockdown COVID-19 in LaLiga™.

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) forced a stoppage in the 2019/2020 season of LaLiga™, possibly influencing performance indicators in the return to competition. Therefore, here, we evaluated whether the stoppage due to the coronavirus 2019 disease (COVID-19) lockdown influenced physical performance compared to the start of LaLigaTM in terms of high-intensity efforts. Using a semi-automatic, multiple-camera system, running activities during 22 matches were analyzed. We compared the first 11 matches of the season (pre-lockdown) with the 11 matches just after the restart of LaLiga™ (post-lockdown). The results showed higher (p < 0.05) performance in the pre-lockdown period compared with the post-lockdown period, including in medium-speed running (14.1-21 km/h), high-speed running (21.1-24 km/h), and sprinting speed running distances (>24 km/h). However, the number of accelerations/min and decelerations/min were significantly higher during the post-lockdown period. Therefore, we conclude that the stoppage due to the COVID-19 lockdown generated lower physical performance in the post-lockdown period compared with the pre-lockdown period, most likely due to the accumulation of matches (congested schedules).

Which Are the Most Determinant Psychological Factors in Olympic Shooting Performance? A Self-Perspective from Elite Shooters.

Psychological aspects like anxiety, injuries' effects, professional psychological support (PPS), psychological training (PT), or athlete-coach relationships could influence shooters' performance. This study tried to determine which aspects were critical from the shooters' perspective. Eight elite shooters were interviewed. After using qualitative methods, the following categories were obtained: importance of PT; anxiety and competition relationship; mental preparation; PPS; stress during training; injuries' psychological effects and coach's influence. PT is important for shooter's performance, being PPS a key aspect. Moreover, anxiety levels are critical, raising during the pre-competitive period and oscillating during competition. Furthermore, shooters considered more effective the stress placed on training by the coach than by themselves. Accordingly, the coach plays a key role. Surprisingly, injuries did not affect shooters psychologically, nor in their competitive performance. We conclude that the combination of PPS, shooter competitive experience and the optimal coach's work can promote a greater performance in Olympic shooting.

Effects on Strength, Power and Speed Execution Using Exercise Balls, Semi-Sphere Balance Balls and Suspension Training Devices: A Systematic Review.

Research in instability has focused on the analysis of muscle activation. The aim of this systematic review was to analyse the effects of unstable devices on speed, strength and muscle power measurements administered in the form of controlled trials to healthy individuals in adulthood. A computerized systematic literature search was performed through electronic databases. According to the criteria for preparing systematic reviews PRISMA, nine studies met the inclusion criteria. The quality of the selected studies was evaluated using STROBE. The average score was 14.3 points, and the highest scores were located in 'Introduction' (100%) and 'Discussion' (80%). There is great heterogeneity in terms of performance variables. However, instability seems to affect these variables negatively. The strength variable was affected to a greater degree, but with intensities near to the 1RM, no differences are observed. As for power, a greater number of repetitions seems to benefit the production of this variable in instability in the upper limb. Instability, in comparison to a stable condition, decreases the parameters of strength, power, and muscular speed in adults. The differences shown are quite significant in most situations although slight decreases can be seen in certain situations.

What Is the Relevance in the Passing Action between the Passer and the Receiver in Soccer? Study of Elite Soccer in La Liga.

Soccer is a high-complexity sport in which 22 players interact simultaneously in a common space. The ball-holder interacts with their teammates by passing actions, establishing a unique communication among them in the development of the game in its offensive phase. The main aim of the present study was to analyze the pass action according to the trajectory of the ball receiver and the space for receiving the ball in terms of success at the end of play. Twenty La Liga 2018/2019 matches of two elite teams were analyzed. A system of notational analysis was used to create 11 categories based on context, timing and pass analysis. The data were analyzed using chi-squared analysis. The results showed that the main performance indicators were the efficiency of the pass, the zone of the field, the trajectory of the receiver and the reception space of the ball, which presented a moderate association with the end of play (p < 0.001). We concluded that receiving the ball on approach and in separation increased the probability of success by 5% and 7%, respectively, and a diagonal run increased the probability by 7%. Moreover, the combined analysis of these variables would improve the team performance.

The Impact of Covid-19 and the Effect of Psychological Factors on Training Conditions of Handball Players.

The spread of COVID-19 has altered sport in Spain, forcing athletes to train at home. The objectives of the study were: (i) to compare training and recovery conditions before and during the isolation period in handball players according to gender and competitive level, and (ii) to analyse the impact of psychological factors during the isolation period. A total of 187 participants (66 women and 121 men) answered a Google Forms questionnaire about demographics, training, moods, emotional intelligence, and resilience sent using the snowball sampling technique. T-test and analysis of variance (ANOVA) were used to compare sport level and gender differences. Linear regressions were used to analyse the psychological influence on training. Handball players reduced training intensity (in the whole sample; p = 0.44), training volume (especially in professional female handball players; p < 0.001), and sleep quality (especially in professional male handball players; p = 0.21) and increased sleep hours (especially in non-professional female players; p = 0.006) during the isolation period. Furthermore, psychological factors affected all evaluated training and recovery conditions during the quarantine, except for sleep quantity. Mood, emotional intelligence, and resilience have an influence on physical activity levels and recovery conditions. In addition, training components were modified under isolation conditions at p < 0.001. We conclude that the COVID-19 isolation period caused reductions in training volume and intensity and decreased sleep quality. Furthermore, psychological components have a significant impact on training and recovery conditions.

Perceptual visual skills in young highly skilled basketball players.

A simple method was designed to evaluate visual abilities such as disance visual acuity, binocular horizontal visual field, simple and choice visual reaction times, and stereoscopic vision in skilled 11- to 13-yr.-old basketball players participating in a 15-day summer training camp. On a test battery, visual abilities were monitored in 473 players of the Spanish Basketball Federation over a 5-yr. period. The players showed outstanding scores on distance visual acuity and stereoscopic vision, and good visual reaction times and horizontal visual fields. When scores were compared by sex and age, significant differences on certain visual measures were observed. Many layers showed crossed eye-hand dominance. Visual screening programs may help promote visual health among junior basketball players and could be used for performance training.