Applying the constraints-led approach to facilitate exploratory learning of the volleyball serve.

Exploration is an important feature for successfully learning motor skills. However, game rules such as one attempt to serve in volleyball could discourage exploration due to an individual's fear of making a mistake and forfeiting a point. The constraints-led approach is a coaching methodology that encourages exploration by selectively manipulating task constraints such as rules. Therefore, the aim of this study was to examine whether the addition of the task constraint of a second serve would encourage volleyball players to use their first serve to explore their action capabilities. Forty male high school students competed in two volleyball games; a regulation (single serve) game and a modified (2-serve) game. Participants reported that having a second chance at serving allowed them to feel more confident and relaxed which facilitated the exploration of their serving capability. In the 2-serve game, participants attempted a more powerful (M = 60.3 km/hr), and complex (M = 44.5% jump topspin serves) first serve, compared to the regulation game (M = 55.6 km/hr; M = 25.2% jump topspin serves). Findings suggest that to facilitate learning of motor skills, it is important to manipulate the practice environment using task constraints to address the factors that restrict exploration.

Causal inference did not detect any effect of jump load on knee complaints in elite men's volleyball.

The aim was to determine how jump load affects knee complaints in elite men's volleyball. We collected data from four men's premier league volleyball teams through three seasons in a prospective cohort study (65 players, 102 player-seasons). Vert inertial measurement devices captured the jump load (jump frequency and jump height) from 21 088 daily player sessions, and knee complaints were reported in 3568 weekly OSTRC-O questionnaires. Mixed complementary log-log regression models described the probability of (i) experiencing symptoms if players were currently asymptomatic, (ii) worsening symptoms if players had symptoms, and (iii) recovery from knee complaints. Based on our causal assumptions, weekly jump load was modeled as the independent variable, adjusted for age (years), weight (kg), position on volleyball team, and past jump load. No certain evidence of an association was found between weekly jump load and probability of (i) knee complaints (p from 0.10 to 0.32 for three restricted cubic splines of load), (ii) worsening symptoms if the player already had symptoms (p from 0.11 to 0.97), (iii) recovery (p from 0.36 to 0.63). The probability of knee complaints was highest for above-average weekly jump load (~1.2% for an outside hitter with mean age and height) compared with low loads (~1%) and very high loads (→ ~ 0%). The association between jump load and knee complaints risk remains unclear. Small differences in risk across observed jump load levels were observed. It would likely require substantially increased sample sizes to detect this association with certainty.

Effects of shoe collar height and limb dominance on landing knee biomechanics in female collegiate volleyball players.

Volleyball-specific footwear with higher collar heights (a mid-cut shoe) are worn to restrict ankle motion. Reduced ankle dorsiflexion has been associated with increased frontal plane motion and injury risk at the knee. With the high frequency of unilateral landings in volleyball, the purpose of this study was to determine the effect of volleyball-specific shoes and limb dominance on knee landing mechanics in collegiate volleyball players. It was hypothesized that participants would exhibit smaller sagittal plane and greater frontal plane knee joint mechanics in mid-cut and dominant limb and that vertical and posterior directed ground reaction forces would be greater wearing mid-cut, yet similar between limbs. Seventeen female volleyball players performed unilateral landings on each limb in mid-cut and low-top volleyball shoes. For shoe main effects, smaller peak dorsiflexion angle and internal peak plantarflexion moment and greater peak medial ground reaction force were found in the mid-cut but with no impact on knee mechanics. For limb main effects, the internal peak knee abduction moment was greater in the dominant limb. Greater peak lateral ground reaction force was found in the interaction between the non-dominant limb and low-top. Further research is warranted to better understand shoe and limb impact in volleyball players.

Ground reaction forces better than center of pressure differentiate postural control between young female volleyball players and untrained peers.

A comprehensive explanation of the relationship between postural control and athletic performance requires compare body balance in athletes with their never training counterparts. To fill this gap in relation to volleyball, the aim of this study was to compare the balance of intermediate adolescent female players (VOL, n = 61) with inactive peers (CON, n = 57). The participants were investigated in normal quiet stance during 20 s trials on a Kistler force plate. The traditional spatial (amplitude and mean speed) and temporal (frequency and entropy) indices were computed for ground reaction forces (GRF) and center-of-pressure (COP) time-series. The spatial parameters of the both time-series did not discriminate the two groups. However, the temporal GRF parameters revealed much lower values in VOL than in CON (p < .0001). This leads to three important conclusions regarding posturography applications. First, GRF and COP provide different information regarding postural control. Second, measures based on GRF are more sensitive to changes in balance related to volleyball training and perhaps to similar training and sports activity regimens. And third, the indicators calculated based on these two time series can complement each other and thus enrich the insight into the relationship between balance and sports performance level.

Does dynamic balance affect cube mental rotation task in badminton vs. volleyball female players?

BACKGROUND: Changing from a static to a dynamic balance condition could affect the performance of a cognitive task such as mental rotation. Thus, the main goal of this study is to investigate aspects of visual-spatial cognition between two non-contact sports (i.e., badminton and volleyball) in different upright conditions (i.e., standing position, frontal balance, and sagittal balance). METHODS: Thirty-five volunteer female sports and physical education students, fourteen specialists in badminton and twenty-one specialists in volleyball agreed to participate in this study. Each of the assessments was a 3D cube mental rotation task with and/or without balance exercises (i.e., frontal and/or sagittal balance) on a wobble board. Five stimuli were used in the mental rotation task (i.e., 45°, 135°, 180°, 225° and 315° for objected-based cube condition with egocentric transformation) which included pairs of standard and comparison images. RESULTS: The findings indicate that there was a notable decrease (p < 0.001; d = 1.745) in response time in both dynamic balance conditions (i.e., frontal and sagittal balance) compared to standing position condition. In addition, results revealed significant interaction between balance conditions (i.e., frontal and/or sagittal balance) and groups (i.e., badminton and volleyball) in the response time at 225° angle and in the error percentage. CONCLUSIONS: In sum, dynamic balance is also an activity that involves mental manipulation of objects in 3D space, which can enhance badminton and volleyball female players' ability to rotate 3D cube stimuli.

The effect of flywheel complex training with eccentric-overload on muscular adaptation in elite female volleyball players.

This study aimed to compare the effects of 8 weeks (24 sessions) between flywheel complex training with eccentric overload and traditional complex training of well-trained volleyball players on muscle adaptation, including hypertrophy, strength, and power variables. Fourteen athletes were recruited and randomly divided into the flywheel complex training with an eccentric-overload group (FCTEO, n = 7) and the control group (the traditional complex training group, TCT, n = 7). Participants performed half-squats using a flywheel device or Smith machine and drop jumps, with three sets of eight repetitions and three sets of 12 repetitions, respectively. The variables assessed included the muscle thickness at the proximal, mid, and distal sections of the quadriceps femoris, maximal half-squats strength (1RM-SS), squat jump (SJ), countermovement jump (CMJ), and three-step approach jump (AJ). In addition, a two-way repeated ANOVA analysis was used to find differences between the two groups and between the two testing times (pre-test vs. post-test). The indicators of the FCTEO group showed a significantly better improvement (p < 0.05) in CMJ (height: ES = 0.648, peak power: ES = 0.750), AJ (height: ES = 0.537, peak power: ES = 0.441), 1RM-SS (ES = 0.671) compared to the TCT group and the muscle thicknes at the mid of the quadriceps femoris (ES = 0.504) after FCTEO training. Since volleyball requires lower limb strength and explosive effort during repeated jumps and spiking, these results suggest that FCTEO affects muscular adaptation in a way that improves performance in well-trained female volleyball players.

Hormonal and psychological influences on performance anxiety in adolescent female volleyball players: a multi-approach study.

Background: The neuroendocrine system has important implications for affiliation behavior among humans and can be used to assess the correlation between social relationships, stress, and health. This can be influenced by social closeness; this aspect is the closeness towards another individual or a group of individuals such as a sports team. Sports performance anxiety is considered an unpleasant emotional reaction composed of physiological, cognitive, affective, and behavioral components. This motivates us to learn about the process that can influence the outcome of competition. Hormones and genetics would seem to influence outcome and performance. In this regard, many studies have focused on the exercise response as a function of ovarian hormones and it has been observed that progesterone is a hormone that plays a key role in reducing anxiety, and thus stress, in humans and other animals. On the other hand, high cortisol concentrations are known to contribute to increased anxiety levels. However, the salivary alpha-amylase (sAA) enzyme has been suggested as marker of acute stress than cortisol. Genetics also seem to influence anxiety and stress management as in the case of brain-derived neurotrophic factor (BDNF) and striatal dopamine transporter (DAT). Therefore, the study aims to investigate social closeness, as a measure of sports team cohesion that can influence athletes' performance results, and its ability to influence the secretion of hormones, such as progesterone and cortisol, that affect the management of sports anxiety while also taking into account genetic background during a volleyball match. Methods: Twenty-six female volleyball players who volunteered participated in this study (mean ± SD: age, 12.07 ± 0.7 years), and played in the final of the provincial volleyball championship in Palermo. All girls were during the ovarian cycle, in detail between the follicular and early ovulatory phases. Results: The results showed a significant decrease in salivary cortisol only in the winning group (p < 0.039). In fact, whilst in the latter the pre-match level was 7.7 ng/ml and then decreased to 4.5 ng/ml after the match, in the losers group change was not statistically significant (7.8 ng/ml vs 6.6 ng/ml pre- and post-match). As to the sAA concentration, the winning team showed a statistically significant variation between pre- and post-match than the losers (166.01 ± 250 U/ml vs 291.59 ± 241 U/ml) (p = 0.01). Conclusion: Analyzing the results of the SAS-2 psychological test it is highlighted that, on average, the loser group was more anxious than the winning group, and this contributed to the final result. In conclusion, there is strong evidence supporting the state of the art that many factors can affect performance anxiety and thus the performance itself.

Prevalence of sunscreen use and sunburn in Greek athletes: a cross-sectional study.

BACKGROUND: Athletes participating in outdoor sports are in a high-risk category for prolonged sun exposure. This study investigates whether swimmers and beach volleyball athletes adopt appropriate measures to protect their skin from the sun. Sunscreens play a key role in protecting the skin from solar radiation and preventing premature aging. The study assesses the frequency of sunscreen use and the incidence of sunburn among athletes. METHODS: Athletes completed a self-administered questionnaire regarding their sun protection and exposure habits. Participants aged 9 to 60 years, engaged in swimming (N.=1047) and beach volleyball (N.=785), were included in this study. RESULTS: In the group of swimmers (N.=858), a notable percentage never used sunscreen, and among those who did, (N.=137), natural products were predominantly applied. Gender differences revealed a significantly higher sunscreen usage (P<0.001) among female swimmers compared to males. Among beach volleyball athletes, sunscreen use was notably higher (90%), with 55.6% applying natural sunscreen and 44.4% opting for non-natural alternatives. Regarding the incidence of sunburn, the occurrence among both male and female swimmers was observed to be very low. Among those with sunburn, females exhibited a significantly higher frequency than males (P<0.001). Conversely, in beach volleyball athletes, sunburn affected a higher percentage of males (49.8%) than females (43.9%). CONCLUSIONS: Sunscreen utilization is notably insufficient among athletes, reflecting a limited awareness of the potential risks associated with sun exposure, even though they frequently suffer from sunburn. This heightened susceptibility places them at an increased risk of developing skin lesions. Initiating and disseminating awareness campaigns that specifically emphasize the importance of sunscreen use within the outdoor sports community is imperative.

Differences in training load, jump performance and injury occurrence in elite youth volleyball players.

BACKGROUND: External and internal training load are used to monitor training effects in volleyball. Occurrence of injuries in volleyball is dependent of training loads and state of fitness but also playing positions and gender. This study aims to investigate the impact of gender and playing positions on injury occurrence among young volleyball players, considering both training loads and fitness levels. METHODS: Conducted from September 2021 to May 2022, this study involved 37 elite young volleyball players, comprising 16 female (176.8±3.6 cm; 65.3±5.7 kg; 13.9±1.1 years old) and 21 males (189.6±7.3 cm; 77.4±9.5 kg; 14.7±1.2 years old). G-Vert accelerometer was used to quantify training load. During these sessions, RPE, state of fitness and occurrence of injuries, were collected using a daily questionnaire. RESULTS: The primary findings indicate that males demonstrated a higher number of jumps, mean intensity, mean training load per session, and reported higher fitness levels compared to females (P<0.001). However, females were more injured than males (P<0.001). Setters were identified as the players with the highest jump frequency, albeit at lower heights and intensities than their counterparts (P<0.001). Among males, middle blockers exhibited the highest mean intensity and training load per session (P<0.01). CONCLUSIONS: The elevated frequency of injuries and a worse reported fitness levels among females, despite lower training loads, suggests a potential deficiency in physical preparation among young women, particularly in terms of their ability to perform repeated high-intensity jumps.

Is There a Relationship Between Birth Quartile and Vertical Jump Performance Among Young Male Elite Volleyball Athletes?

Vertical jump is an important skill that influences volleyball performance. In this study, we analyzed the relationship between vertical jump performance and birth quartile of Brazilian male youth volleyball players. We calculated chi-square goodness-of-fit tests to compare the athletes' birthdate distributions in quarters of their birth years (Q1, Q2, Q3, and Q4) according to player age categories (U17, U18, U19, and U21). We calculated one-way ANOVAs to compare spike jump and block jump heights of players born in different quarters of the same year. Overall, we found a relative age effect (i.e., more players with birth dates early in the birth year) in U17 (p < .001), U18 (p < .001), U19 (p < .001), and U21 (p = .04). Regarding vertical jump performance, U18 athletes born in Q2 reached higher spike jump heights (p = .006) and block jump heights (p = .002) than athletes born in Q4, and U19 athletes born in Q1 reached higher block jump heights than athletes born in Q3 (p = .049). There were no significant differences in vertical jump performance across birth quartiles among U17 and U21 athletes. Thus, a relative age effect was present in all age categories but not always reflected in vertical jump performance. Volleyball coaches and policymakers are still advised to employ strategies to ensure fairer opportunities for players born later in the year of their eligibility dates, as we found RAE to be sometimes, but not always, related to higher spike or block jump heights even among these older adolescents and young adult athletes.

Analyzing the psychological variables linked to performance in beach volleyball: an integrative review and practical recommendations / Análisis de las variables psicológicas vinculadas al rendimiento en voleibol playa: una revisión integradora y recomendaciones prácticas / Análise das variáveis psicológicas ligadas ao desempenho no voleibol de praia: uma revisão integrativa e recomendações práticas

Beach volleyball is an important team sport in which physical, technical, tactical,and psychological/social aspects are fundamental to sporting performance. However, this is the first review to analyse scientific production on psychological variables in beach volleyball. This is an integrative review in which a systematic search was carried out in five electronic databases (PubMed/MEDLINE, SPORTDiscus/EBSCO, SciELO, Scopus and BIREME) until September 2022. The terms used were "beach volleyball" OR "voleibolde praia" OR "vôlei de praia". In addition, the search included research with athletes, acute and chronic outcomes, and studies of various methods (e.g.,experimental, observational) involving psychological variables. The initial search identified 652 articles, and after the manual search and application of the inclusion criteria, 18 studies were integrated into a final synthesis.Most of the studies were published between 2011 and 2022 (n= 14; 77.78%). Observational design was the main method used (n= 10; 55.56%). The studies were grouped into nine major topics for synthesis: stress situation, activation levels, concentration, goal orientation and motivation, mental fatigue and performance, anxiety,and performance, discouraging environments, relationships between team members, coping strategies. In general, social relationships and self-control appear significant for performance; thus,coaches must serve as role models for players and sports psychologists can aid in monitoring psychological variables, team dynamics, and develop psychological skills.(AU)

El vóleyplaya es un importante deporte de equipo en el que los aspectos físicos, técnicos, tácticos y psicológicos/sociales son fundamentales para el rendimiento deportivo. Sin embargo, esta es la primera revisión que analiza la producción científica sobre variables psicológicas en vóleyplaya. Se trata de una revisión integradora en la que se realizó una búsqueda sistemática en cinco bases de datos electrónicas (PubMed/MEDLINE, SPORTDiscus/EBSCO, SciELO, Scopus y BIREME) hasta septiembre de 2022. Los términos utilizados fueron "beach volleyball" OR "voleibol de praia" OR "vôlei de praia". Además, la búsqueda incluyó investigaciones con atletas, intervenciones agudas y crónicas, estudios de diversos métodos (e.g., experimentales, observacionales) que implicaran variables psicológicas. La búsqueda inicial identificó 652 artículos y, después de la búsqueda manual y la aplicación de los criterios de inclusión, 18 estudios se integraron en una síntesis final. La mayoría de los estudios fueron publicados entre 2011 y 2022 (n= 14; 77.78%). El diseño observacional fue el principal método utilizado (n= 10; 55.56%). Los estudios se agruparon en nueve grandes temas para la síntesis: situación de estrés, niveles de activación, concentración, orientación a objetivos y motivación, fatiga mental y rendimiento, ansiedad y rendimiento, entornos desalentadores, relaciones entre los miembros del equipo, estrategias de afrontamiento. Las relaciones sociales y el autocontrol parecen ser importantes para el rendimiento, por lo quelos entrenadores deben comportarse como modelos para los deportistas. Además, los psicólogosdeportivos pueden ayudar a controlar las variables psicológicas, la dinámica del equipo y a desarrollar habilidades psicológicas.(AU)

O voleibol de praia é um importante esporte coletivo em que aspectos físicos, técnicos, táticos e psicológicos/sociais são fundamentais para o desempenho esportivo. No entanto, esta é a primeira revisão que teve como objetivo analisar a produção científica sobre variáveis psicológicas no voleibol de praia. Essa é uma revisão integrativa em que foi realizada uma busca em cinco bases de dados eletrônicas (PubMed/MEDLINE, SPORTDiscus/EBSCO, SciELO, Scopus e BIREME) até setembro de 2022, de forma sistemática. Os temos usados foram “beach volleyball” OU “voleibol de praia” OU “vôlei de praia”. Além disso, foram incluídos nessa busca pesquisas com atletas, intervenções agudas e crônicas, estudos de vários métodos (e.g., experimental, observacional) que envolviam variáveis psicológicas. A busca inicial identificou 652 artigos, após a busca manual e aplicação dos critérios de inclusão, 18 estudos foram integrados a uma síntese final. A maioria dos estudos foi publicada entre 2011 e 2022 (n= 14; 77.78%). O desenho observacional foi o principal método utilizado (n= 10; 55.56%). Os estudos foram agrupados em nove grandes tópicos para síntese: situação de estresse, níveis de ativação, concentração, orientação para metas e motivação, fadiga mental e desempenho, ansiedade e desempenho, ambientes desanimadores, relacionamento entre as partes da equipe, estratégias de enfrentamento. As relações sociais e o autocontrole parecem importantes para o desempenho, portanto treinadores devem se comporta como modelo para os atletas. Além disso, psicólogos do esporte podem ajudar a monitorizar as variáveis psicológicas, na dinâmica da equipa e desenvolver de competências psicológicas.(AU)

Differences in external load among indoor and beach volleyball players during elite matches.

The aim of this cross-sectional study was to examine relationships of external load variables between beach and indoor volleyball amongst individual positions on the team. The movements of eight beach and fourteen indoor female volleyball players were recorded during elite playoff matches; in total, 2,336 three-dimensional trajectories were analyzed. Time-outs and intervals between rallies or sets were excluded from active play time. In both beach and indoor volleyball, 80% of rallies lasted up to 10 s, and players covered 4.5 to 10 m of court during 60% of rally play. Differences in dependent variables of external load were found between independent variables of sports and player positions (p < 0.05). The distance covered in beach volleyball rallies and Player Load™ parameters was significantly higher by up to 23%. The unstable court surface with sand in beach volleyball elevated explosive Player Load™ (accelerations in all three orthogonal planes of motion higher than 3.5 m/s3) in beach volleyball players compared to those of players on stable flooring in indoor. While beach volleyball blocker and defender positions showed no significant difference in parameters between each other, they differed in all parameters when compared to player positions in indoor volleyball. Indoor blocker and libero reached higher loads than setter, outside and opposite positions in various parameters. Factors that influence external load include the larger relative court areas covered by each player in beach volleyball, complexity of players' roles, and game strategy. This data adds to the knowledge of elite match demands in female volleyball. Specified agility-drill distances and times are essential for training optimization and must be supported by scientific observation. Researchers, coaches, and conditioning specialists should find this helpful for achieving a higher degree of training regulation.

Competitive Season-Long Changes in Countermovement Vertical Jump Force-Time Metrics in Female Volleyball Players.

ABSTRACT: Cabarkapa, DV, Cabarkapa, D, Philipp, NM, and Fry, AC. Competitive season-long changes in countermovement vertical jump force-time metrics in female volleyball players. J Strength Cond Res 38(2): e72-e77, 2024-Although force plates remain one of the most widely used tools for neuromuscular performance assessment in applied sports-specific settings, there is still a lack of scientific literature focused on studying changes in countermovement vertical jump (CVJ) performance in team sports such as volleyball, especially within the female athlete population. Thus, the purpose of the present study was to examine season-long neuromuscular performance changes in volleyball players. Eighteen National Association of Intercollegiate Athletics Division-I collegiate female athletes performed 3 maximal-effort CVJs while standing on a uniaxial force plate system sampling at 1,000 Hz at 5 different testing timepoints throughout a competitive season span (∼11 weeks). The testing sessions were separated 2-3 weeks apart and performed at the approximately same time of the day (12:00 hours). Repeated-measures analysis of variance revealed that both concentric and eccentric force-time metrics remain relatively unchanged throughout a regular season span (e.g., concentric peak force and power, eccentric impulse and duration). However, the eccentric metrics such as peak and mean power and peak velocity displayed a slight improvement after a brief tapering period purposely implemented before the post-season competition to optimize the athlete's recovery (∼15, 18, and 14% increase, respectively). In addition, the outcome metrics such as vertical jump height and reactive strength index-modified did not display notable fluctuations across the competitive season span. These findings can help coaches, sports scientists, and strength and conditioning practitioners to obtain a deeper insight into collegiate female athletes' force-time characteristics that may aid with developing adequate training regimens targeted toward optimizing on-court performance.

An insidious rectus abdominis muscle injury in an elite volleyball player: a case report.

BACKGROUND: Structural muscle injuries are characterized by acute and localized onset of pain. Abdominal muscle injuries are an insidious pathology in overhead athletes. However, only a few cases are reported in literature related to volleyball players, where clinical presentation may not have reflected the severity of the lesion. CASE PRESENTATION: An elite volleyball player, a 21-year-old Caucasian female, reported the onset of mild abdominal muscular pain, confirmed on clinical evaluation findings and self-reported symptoms. Abdominal muscle ultrasound was performed following 2 weeks of continuing symptoms. This evidenced a more serious structural muscle injury of the rectus abdominis (type 3b). Having this correct diagnosis allowed a personalized rehabilitation program to be instituted to enable a safe return to play. CONCLUSION: In presence of persistent abdominal muscle pain, even if mild, the possibility of a structural muscle injury must be considered. Clinical evaluation must be complemented by an instrumental evaluation including an ultrasound by an experienced operator for correct diagnosis and the setting of functional recovery related to biological healing.

Risk and protective factors for shoulder complaints in indoor volleyball players: A comprehensive systematic review.

OBJECTIVE: This systematic review aimed to answer the question: "What are the risk and protective factors for shoulder complaints (pain, injury, or problem) in indoor volleyball players?". METHODS: Searches were conducted in electronic databases: PubMed/MEDLINE, Embase, CINAHL, and SPORTDiscus, as well as reference lists of the included studies. We included studies evaluating potential intrinsic and extrinsic factors associated with shoulder complaints in indoor volleyball players of any country, age, sex, and competitive level. The Quality in Prognosis Studies (QUIPS) tool was used to assess the risk of bias. RESULTS: The risk factors for shoulder complaints in volleyball players were identified through four prospective studies, which exhibited a moderate to low risk of bias. These factors included previous shoulder pain or injury, playing in outside and opposite positions, subacromial bursa thickening, and having an average external rotator (ER) isokinetic eccentric torque lower than the average internal rotator (IR) concentric torque. Protective factors were enhancing shoulder IR and ER isokinetic eccentric strength, being male sex, being older, and maintaining a concentric strength ratio ER/IR within the 0.60-0.75 range. CONCLUSIONS: This systematic review highlights risk factors that clinicians and researchers should consider when assessing and tracking indoor volleyball players.

A sports-related injury prevention program for Dutch youth volleyball players: Process evaluation alongside a quasi-randomized controlled trial.

OBJECTIVE: This process evaluation aimed to gain insight into the implementation of the VolleyVeilig Youth program by Dutch volleyball clubs within the context of an effectiveness trial. METHODS: We applied the UK Medical Research Council framework for process evaluations and assessed the context, implementation and mechanisms of impact. Trainers participating in the effectiveness trial were asked to complete a questionnaire at the end of the study. A subsample of the trainers based on the self-reported adherence score was invited to participate in an interview accordingly. We used a thematic analysis to present the data. RESULTS: Thirty-one trainers (100%) completed the questionnaire, and seven agreed to participate in an interview. Although adherence gradually decreased over the volleyball season, most trainers reported partially adhere with the program until the end of the study. The main themes included factors associated with the (1) VolleyVeilig Youth program, (2) trainer, (3) players, and (4) volleyball club. CONCLUSION: Although (partial) adherence to the VolleyVeilig Youth program was high in this study, implementation strategies must be developed to target the barriers reported by the trainers before the program can be successfully implemented nationwide in the Netherlands.

Applying Unsupervised Machine Learning Models to Identify Serve Performance Related Indicators in Women's Volleyball.

In volleyball, the effect of different factors on serve performance has usually been analyzed with traditional statistical techniques such as logistic regression or discriminant analysis. Purpose: In this study, two of the main models used in unsupervised machine learning (cluster and principal component analysis) were applied to achieve these objectives: (a) to create groups of players considering their serve coefficient, age, height, and team ranking, and (b) to identify which variables related to the serve (type and performance), the players (role, age, and height), and the teams (ranking, match location, and quality of opposition) most explained the total variance of the data during an entire women's volleyball season. Method: A total of 20,936 serves were analyzed during the 132 matches played in the 2017-2018 season in the Liga Iberdrola (women Spanish first division). The variables were related to the serving action (type of serve and performance), the players' traits (player role, age, and height), and the teams' characteristics (final ranking, match location, quality of opposition, and tournament). Results: Cluster analysis showed five groups of players differing in age, serve coefficient, team ranking, and height. Principal component analysis showed how the first five components explained 72.12% of the total variance. From these components, serve coefficient, team ranking, match location, quality of opposition, and player role each contributed more than 10%. Conclusions: These findings can help coaches to improve talent selection and players' development according to competition demands.

Youth Sport Participation Trends Across Europe: Implications for Policy and Practice.

Purpose: Despite the known health and wellbeing benefits of taking part in sport for children and adolescents, it is reported that sports participation declines during adolescence. The purpose of this study was to explore current organized youth sport participation rates across Europe for both males and females and update current understanding. Method: Sport participation registration data was collected for 18 sports from 27 countries. In total, participation data was collected from over 5 million young people from Under 8s (U8s) to Under 18s (U18s). Differences in the participation rates between age categories were investigated using a generalized linear mixed effects model. Results: Overall, males were four times more likely to participate in organised youth sport than females' participants, with this trend apparent across all age categories and across most sports. There was a significant decrease across sports in participation rates for males during adolescence from U14-U16 and U16-U18. There was a significant decrease in participation rates for females from U14-U16 for most sports except but an increase in participation rates from U16-U18 for 12 out of 18 sports. Soccer (1262%), wrestling (391%) and boxing (209%) were the sports that had greater male sport participation rates. In contrast, dance sports (86%) and volleyball (63%) had more female participants than males. This research shows male sports participation is significantly greater than female in youth sport across Europe. Conclusion: Furthermore, findings showed that for both male and female participants, participation rates increased from U8-U14 for the majority of sports followed by reduced participation rates during adolescence. Findings of this research can be used by national governing bodies and sporting organizations to inform youth sport participation initiatives.

Concurrent Validity and Reliability of In-Field Vertical Jump Performance Measures on Sand Surfaces.

ABSTRACT: Wirtz, S, Julian, R, Schmale, R, and Eils, E. Concurrent validity and reliability of in-field vertical jump performance measures on sand surfaces. J Strength Cond Res 38(4): 687-693, 2024-Beach sports, such as handball, volleyball, and soccer, involve dynamic actions, primarily jumps. Nonetheless, there is a need for more established measurement devices that are both valid and feasible in accurately evaluating jumping performance on sand surfaces. This study aims to assess the reliability and concurrent validity of MyJump2 and an inertial measurement unit (VERT) for quantifying countermovement jump performance on the sand. Twenty-one subjects performed 5 countermovement jumps on the sand. Jumping height was measured simultaneously by a force plate, VERT, and MyJump2. The VERT and MyJump2 reliability measures were evaluated using the intraclass correlation coefficients (ICC) for both absolute agreement (ICC 2,1 ) and consistency (ICC 3.1 ). The day-to-day reliability of both devices and the interrater and intrarater reliability of the MyJump2 were assessed. The concurrent validity of the VERT and MyJump2 was assessed using ICCs 2.1, 3.1 and Bland-Altman plots. A near-perfect agreement was seen for intrarater (ICC = 0.98) and interrater (ICC = 0.98) reliability of the MyJump2. Moreover, a near-perfect agreement was also observed when comparing the MyJump2 with the force plate (ICC = 0.92), with a mean bias of -2.31 cm. The VERT device only demonstrated a moderate agreement (ICC = 0.55) with a mean bias of 6.31 cm compared with the force plate, despite showing good day-to-day reliability (ICC = 0.79). The study's results indicate that MyJump2 is valid and reliable for assessing jump heights on sand surfaces, whereas VERT cannot be recommended.