Journal of Human Kinetics最新文献

Sprint-specific exercises (SSEs) are believed to train force, power and/or velocity qualities involved in the acceleration phase of sprinting. However, the kinetics and the kinematics of such exercises have never been explored. The aim of this study was to compare mechanical variables (horizontal and vertical forces, horizontal velocity of the centre of mass and the ratio of force) between SSEs and an all-out 40-m sprint acceleration (Sref). These variables were measured over each situation (Sref and 14 SSE) using six track-embedded force plates. The horizontal forces and velocities were either lower or equal to those of the Sref (SSE grand average deviation from FVP ~ -0.29 N∙kg^-1 for force; SSE grand average from Sref ~ -0.14 m∙s^-1 for velocity), while vertical force output was mostly greater in the SSE than the Sref (SSE mean deviation from Sref ~0.49 N∙kg^-1). The ratio of force was lower or equal for the SSE compared to Sref. Despite large inter-individual variability, these SSEs seem useful to stimulate vertical force production, and not horizontal as hypothesised by coaches. These results suggest the importance of analysing the SSE used during training, from a force-velocity point of view, to better characterize their effectiveness.

This study explored the effects of sport motivation on athlete burnout among adolescent athletes and examined the mediating roles of life satisfaction and mental toughness. A total of 638 adolescent athletes (mean age = 15.64 ± 2.28 years) were assessed using the athletic motivation scale, the satisfaction with life scale, the adolescent mental toughness scale, and the athlete burnout questionnaire. Data were analyzed using SPSS Process for chain mediation analysis. Results indicated that sport motivation negatively predicted athlete burnout in both male (r = -0.523) and female athletes (r = -0.491). For male athletes, the total effect of sport motivation on athlete burnout was -0.374, with direct and indirect effects of -0.188 and -0.186, respectively. For female athletes, the total effect was -0.601, with direct and indirect effects of -0.363 and -0.238, respectively. Male athletes showed indirect effects through mental toughness (effect = -0.174; share = 46.52%) and the chain mediation of life satisfaction and mental toughness (effect = -0.072; share = 19.25%). Female athletes exhibited indirect effects through life satisfaction (effect = -0.043; share = 7.15%), mental toughness (effect = -0.151; share = 25.12%), as well as the chain mediation of life satisfaction and mental toughness (effect = -0.044; share = 7.32%). This study highlights the role of sport motivation in reducing athlete burnout. For female athletes, burnout was influenced by all three mediating pathways (life satisfaction, mental toughness, and their chain mediation). For male athletes, the effects were predominantly mediated through mental toughness and the chain mediation of life satisfaction along with mental toughness.

This study investigated the talent selection processes implemented in youth and adult national futsal teams. The initial database provided by the Portuguese Football Federation included 668 male futsal players, and statistical analysis was conducted with varying sample sizes. Binary logistic regressions were performed to determine the influence of futsal participation on the likelihood of achieving international status at the adult level. Subsequently, the age of first registration was plotted against the national team in which the first international appearance was recorded. Finally, the selection, re-selection, and de-selection of players from the under-17 youth national team to the adult team were described using frequencies and percentages. For the total sample, the results indicated that an earlier age at first registration, participation in the 1^st Division, involvement in foreign competitions, and engagement with multiple clubs increased the likelihood of being selected for the international team. The analysis also considered the year in which youth national teams were developed. Before 1999, players demonstrated earlier registration ages; however, the timing of starting futsal practice became less relevant to attaining international adult status after 1999. Furthermore, a negligible percentage of youth national team players progressed to the senior national team, highlighting the collectivist approach employed by futsal national coaches. The findings of this study suggest that the transition of talent from youth to adult national teams warrants further investigation. Coaches should develop strategies to promote the development of youth talent as they progress towards adult-level status.

The purpose of this study was to examine the kinematic and kinetic changes in overhead squats (OHSs) with increasing loads and clarify the relationship between OHS movement and shoulder joint flexibility. Fourteen male college students randomly performed OHSs using 20% of their body mass (BM), 40% of their BM, and a plastic pipe (no load). The motion and ground reaction forces during OHSs were recorded. The relative peak torque of the hip under the 20% and 40% BM conditions during both negative and positive phases of the OHS was significantly greater than that under the no-load condition, while the relative peak torque of the knee did not increase. The relative peak torque of the hip was negatively correlated with the angles of the lower trunk at the lowest point of the center of mass (CM). In relation to the movement of the OHS and shoulder joint flexibility, a correlation was observed between the angle of the lower trunk at the lowest point of the CM and the shoulder flexibility test score (r = 0.561-0.598, p < 0.05), suggesting that a flexible shoulder joint could lead to the lower trunk leaning forward during the OHS. These results reveal that in the overhead squat, where the relative load to body weight is smaller compared to the normal squat, an increase in the load leads to an increase in hip torque without a corresponding increase in knee torque. Furthermore, the increase in hip torque is influenced by the angle of the lower trunk.

Regular assessment of clinical measurements of trunk rotation flexibility that are valid and reliable is necessary to minimize the risk of injury and optimize performance in tennis players who perform repetitive trunk rotation. The objectives of this study were to investigate: (1) the intra-rater, inter-rater, and test-retest reliability of the leg lateral reach test (LLRT) in tennis players; (2) the minimum detectable change in the leg lateral reach test in tennis players; and (3) the correlation between leg lateral reach and seated rotation tests in tennis players. Twenty-four adolescent tennis players were recruited for the study. To ascertain the reliability of the leg lateral reach test, two designated raters (rater 1 and rater 2) evaluated each participant with the test 5-7 days apart (session 1 and session 2). The leg lateral reach distances and the seated rotation angle from session 1 were correlated to evaluate the validity. The intra-rater and inter-rater analysis found almost perfect reliability (ICC ≥ 0.835, SEM ≤ 2.47 cm; ICC ≥ 0.881, SEM ≤ 2.02 cm, respectively). The correlation between the distance of the lateral leg reach for the dominant and non-dominant sides and the angle of seated rotation was fair (r 0.441 and 0.406, respectively). This study demonstrates the leg lateral reach test as a reliable and valid screening tool, accurately predicting the range of thoraco-lumbo-pelvic rotation in adolescent tennis players.

Handball referees face significant physical demands during the games that can influence the accuracy of their decisions. The aim of this study was to compare the movement profile of the referees during the men's and women's EHF 2022 EUROs. A total of 60 referees were evaluated using a local positioning system which provided data on their total distance, pace, accelerations, decelerations, and time spent in different speed zones. To automate the proposed methodology, a system was designed based on three phases: 1) capture of information on the activities and the context of the match through sensor networks, the LPS system and WebScraping techniques; 2) information processing based on Big Data Analytics; 3) extraction of results based on a descriptive analytics approach. The analysis revealed that referees in the women's tournament covered greater total and high-speed distances, but the accelerations were greater in the men's championship. Despite these differences, the referees' running pace, analyzed in fixed 5-min time intervals, followed a similar pattern across tournaments, identifying the first 10 min of play as the most demanding scenarios. These findings highlight the importance of adapting physical training of referees according to the specific demands of each competition.

The human gut microbiome, a diverse community of microorganisms, plays a crucial role in digestion, metabolism, immune function, and brain health. Key metabolites produced by the gut microbiota, such as short-chain fatty acids (SCFAs) and bile acids, are essential for energy production, metabolic regulation, and immune system modulation. The gut microbiome's composition is influenced by factors including diet, exercise, sleep, and age, and disruptions are linked to various health conditions. Elite athletes exhibit unique gut microbiota profiles that contribute to their exceptional performance and recovery. Their microbiomes are not only richer, but also possess unique microorganisms and functional capabilities, alongside distinct genetic landscapes that support their high-level physiological demands. This review focuses specifically on the athletic gut microbiome, exploring how it differs from that of an active or a sedentary individual, adapts to different training phases, extreme conditions like heat and hypoxia, and prolonged exertion. It highlights the dual role of the gut microbiome in both enhancing athletic performance and potentially contributing to disease development, particularly due to the prolonged exertion and stress associated with years of intense competition. The review also explores the implications of microbiome changes following periods of intense physical activity and their impact on the athlete's overall health. Finally, it evaluates athlete-specific interventions, including prebiotics, probiotics, and synbiotics, aimed at mitigating negative effects on the gut microbiome while supporting health and optimizing performance.

The indirect impact of stroke performance on the dynamics of winning and losing points in table tennis has been seldom explored. This study aimed to uncover and contrast the nuances of stroke execution-both the techniques utilized and the strategic ball placements-in four principal types of table tennis matches: right-handed versus right-handed (RRM), right-handed versus left-handed (RLM), left-handed versus right-handed (LRM) and left-handed versus left-handed (LLM). These matches exhibit distinct indirect effects on rally outcomes, categorized as positive (winner-assisting) and negative (momentum-diminishing). Our analysis encompassed 190 men's singles matches with a total of 15916 points played. Employing chi-square tests for multiple bivariate analyses and subsequent post-hoc pairwise comparisons, we found that for the development of winner-assisting strokes, the ball placements from the normal sidespin serve, backspin/no-spin serve, short push, long push, forehand flip, backhand flip, and both non-topspin and topspin loop/drives for both the forehand and the backhand had small to large effects (p < 0.05-0.001, ES: 0.084-0.266). Similarly, for the induction of momentum-diminishing strokes, the ball placements from the aforementioned serves, short/long push, and flips, along with the non-topspin and topspin loop/drives, blocks and lobs, yielded small to moderate effects (p < 0.05-0.001, ES: 0.050-0.206). These insights are invaluable, enabling professionals to grasp table tennis strategies, enhance training, and execute match plans with precision.

The study aimed to examine the effect of various factors in the talent development environment (TDE) on the sport commitment of Chinese athletes and whether this effect differed across various sport levels. We surveyed 176 Chinese athletes using a questionnaire. Stepwise regression and five-fold cross-validation were used to identify key factors in the TDE that influenced sport commitment. Multiple linear regression was then used to examine differences across sport levels. Long-term development focus had a significant positive effect on the sport commitment of sub-elite and elite athletes (p < 0.01 and p < 0.05, respectively). The support network negatively affected sport commitment only in sub-elite athletes (p < 0.01), while long-term development fundamentals positively influenced sport commitment only in elite athletes (p < 0.05). Creating a TDE that aligns with the requirements of long-term development focus is beneficial for enhancing sport commitment. The application of support networks should be directed toward long-term success while avoiding excessive emphasis on short-term success. Although the stage-specific nature of athlete development and the unique characteristics of the China's sports system may limit the immediate effect of long-term development fundamentals on sport commitment in the early stages of an athlete's career, their role in preventing burnout underscores their continued importance. This study provides a theoretical foundation and practical guidance for enhancing sport commitment and offers a potential pathway to addressing premature retirement among Chinese athletes.

This study presents a longitudinal analysis and predictive modeling of elite sprint performance trends from 1976 to 2035, based on a database of over 2,500 results from top 10 male and female finishers in the 100-m, 200-m, and 400-m events. Using regression analysis and time series models, including ARIMA and SARIMA, the study evaluated historical trajectories and predictions, accounting for seasonal effects related to Olympic-year cycles. Results indicated a significant long-term improvement in sprint performances, with the most rapid gains occurring before the year 2000. However, the rate of progress slowed, particularly in the 100-m and 400-m events, suggesting physiological limits may be approaching. ARIMA models predicted marginal improvements by 2035, with projected best times of approximately 10.67 s for women and 9.63 s for men in the 100-m event. Regression models, despite showing strong fits (R² > 0.85), tended to overestimate future performance gains compared to ARIMA, particularly in the speed-endurance-dominated 400-m sprint. Comparative model assessments demonstrated that ARIMA provided superior predictive accuracy, better capturing historical variability and Olympic-cycle peaks. Practical implications suggested that future sprint performance gains would depend more on advancements in biomechanics, individualized training optimization, and sports technology, rather than on natural physiological improvements alone. This study highlights the necessity for integrating machine learning-based forecasting, biomechanical modeling, and strategic periodization to maximize sprinting potential in the coming decades.