Kinesiology, as the scientific study of human movement, has undergone substantial conceptual and structural changes over the past decades. According to Mraković, kinesiology is defined as an empirical, experimentally based science that studies the laws, principles, and patterns of controlled and purposeful physical activity and its effects on the human organism. This definition highlights the scientific and systematic nature of the discipline. The aim of this review paper is to examine the development of kinesiology in the 21st century, with particular emphasis on its paradigm shift from a practice-oriented field toward an interdisciplinary scientific discipline. The analysis is based on foundational and contemporary literature, including empirical and systematic studies . The findings suggest that kinesiology has evolved into a comprehensive field integrating biological, social, and behavioural sciences. Modern kinesiology focuses on health, performance, and human development, addressing global challenges such as physical inactivity and chronic disease. The discipline is increasingly recognised as a central scientific framework for understanding human movement in the 21st century. The review further demonstrates that the future development of kinesiology will depend on interdisciplinary collaboration, methodological standardization, international scientific cooperation, and the integration of emerging technologies such as wearable sensors, artificial intelligence, motion analysis systems, and precision exercise medicine. These developments position kinesiology as a central scientific discipline for addressing contemporary challenges in health, human performance, and physical activity across the lifespan.

Aim: Female athletic performance is shaped by the convergence of menstrual-cycle timing, circadian rhythms, fatigue, and ergogenic supplementation; yet no prior study has examined these factors simultaneously in a sport-specific setting. This study investigated the independent and combined effects of acute caffeine ingestion, calendar-based testing window, time of day, and match-induced fatigue on psychophysiological, cognitive, and physical performance in trained female volleyball players. Methods: Thirteen elite eumenorrheic female volleyball players (age: 24.23 ± 4.06 years) completed a randomized, double-blind, placebo-controlled crossover protocol comprising 12 sessions corresponding to all combinations of testing window (menstrual, follicular, luteal), supplementation (caffeine 6 mg·kg−1 vs. placebo), and time of day (08:00 h vs. 18:00 h). Assessments included the Epworth Sleepiness Scale, Pittsburgh Sleep Quality Index, Spiegel questionnaire, Profile of Mood States, Hooper Index, Stroop task, Countermovement Jump (CMJ), Modified Agility T-Test (MAT), and Reactive Agility Test (RAT), administered before and after a one-hour simulated match. Results: Significant main effects of testing window, caffeine, time of day, and fatigue state were observed across all outcome domains (all p < 0.05). Caffeine reduced daytime sleepiness (F(1,12) = 23.84, p < 0.001, ηp2 = 0.665), enhanced vigor (F(1,12) = 114.10, p < 0.001, ηp2 = 0.905), and improved MAT performance (F(1,12) = 33.27, p < 0.001, ηp2 = 0.735). The follicular window was associated with superior cognitive, neuromuscular, and mood-related outcomes relative to the menstrual and luteal windows. Exploratory higher-order interactions suggested condition-specific caffeine benefits for MAT, RAT, and CMJ, particularly in afternoon post-fatigue conditions; these patterns require replication in larger samples. Conclusions: Acute caffeine ingestion improved several psychophysiological, cognitive, and neuromuscular outcomes in trained female volleyball players, with effects that varied across calendar-based testing windows, time of day, and fatigue state. Individualized supplementation strategies incorporating cycle timing and circadian context remain investigational; prescriptive recommendations require replication in larger, hormonally verified samples before clinical or applied adoption.

Purpose: The main purpose of the study was to examine the reliability and validity of the 30-15 Intermittent Fitness Test (30-15IFT). Methods: Forty-eight young female soccer players (age = 17.33 +/- 1.15 years; height = 175.11 +/- 6.10 cm; weight = 67.20 +/- 7.13 kg) from three national level competitive clubs were recruited. Test-retest reliability was performed 7 days apart and the 30-15IFT outcome measures were correlated against the Bruce continuous running test protocol. Results: Vmax (ICC = .90; CV = 1.02%, P< .001), HRpeak (ICC =.91; CV = 1.00%, P< .001) and VO2max (ICC = .91; CV = 1.10%, P< .001) exhibited high reliability properties. Correlations between the 30-15IFT and continuous running yielded very large effects for Vmax (R= .72; SEE = .65 km*h-1, P< .001), HRpeak (R= .77; SEE = 5.09 b.p.m., P< .001) and VO2max (R= .73; SEE = 1.96 ml*kg-1*min-1, P< .001). Conclusions: This study shows that the 30-15IFT is highly reliable and satisfactory valid tool for assessing aerobic capacity in young female soccer players.

Background:K1 kickboxing is an elite combat sport that combines striking techniques (punches, kicks, knee strikes) with tactical decision-making and anthropometric advantages. Success in K1 matches depends on both technical-tactical (TE-TA) structures and physical characteristics. However, few studies have developed comprehensive predictive models that integrate these factors to explain match outcomes in elite K1 competition. Objective:This study was to identify a model of success that incorporates key technical-tactical (TE-TA) structures and anthropometric characteristics that predict the outcome of kickboxing matches under K1 rules. Methods:A total of 96 qualifying matches for the K1 Final Grand Prix in Japan, comprising 192 fighter appearances from tournaments held between 1995 and 2012, were analyzed using logistic regression. Model fit was evaluated using the Hosmer-Lemeshow test, and discriminative power was assessed via Receiver Operating Characteristic (ROC) analysis. Results:The Hosmer-Lemeshow test (χ 2 = 9.93, p > 0.05) indicated a good model fit, while the Receiver Operating Characteristic ROC analysis (area Under the Curve [AUC] = 0.84 demonstrated high discriminative power. The largest positive effects were observed for the rear-hand uppercut to the head, the lead-hand hook to the head, and the low rear-leg roundhouse kick to the lead leg, with each additional successful execution being associated with a 23.0%, 17.3%, and 12.6% increase in the odds of winning, respectively (e.g., OR = 1.23 for the rear-hand uppercut). Conversely, defensive structures involving hand blocks, whether against punches or leg strikes, were associated with 4.2% and 10.4% decreases in the odds of winning, respectively, suggesting these may be reactive structures taken under pressure. Additionally, each centimeter of greater height was associated with a 9.8% increase in the odds of winning. Conclusion:These findings provide expert coaches and scientists with guidance for optimizing contemporary training systems, enhancing tactical decision-making, and implementing predictive accuracy in elite-level kickboxing.

This exploratory cross-sectional study examined physical activity patterns, menstrual characteristics, and menstrual pain intensity in 53 young women (mean age 19.98 ± 0.72 years). Physical activity during the previous seven days was estimated using the International Physical Activity Questionnaire framework and expressed as MET-min/week, while menstrual pain during the most recent cycle was assessed on a 0–10 numerical rating scale. Severe pain was reported by 19 participants (35.8%), and 39 participants (73.6%) were classified in the high physical activity category. Total physical activity was not significantly associated with pain intensity (Spearman’s rho = .225, p = .105). Moderate physical activity showed a positive association with pain intensity (Spearman’s rho = .428, p = .002), but the cross-sectional design does not permit causal interpretation. Rather than supporting a simple protective effect of greater activity volume, the findings suggest that the relationship between physical activity and menstrual pain may depend on individual symptoms, behavioural responses, measurement context, and unmeasured psychological or clinical factors. Because the sample was small, narrowly distributed by age, and dominated by highly active participants, the results should be interpreted as preliminary. Future studies should use larger and more heterogeneous samples, objective activity monitoring, validated multidimensional dysmenorrhea instruments, and repeated assessments across several menstrual cycles.

Purpose: This study investigated the effect of the Good Behaviour Game (GBG) on targeted motor performance metrics during long jump instruction. Methods: In this randomized controlled trial, 40 middle school students (age: 13.10±.40 years) were equally distributed between experimental and control-groups. The experimental group received the GBG intervention integrated into their regular physical education curriculum, while the control group participated in standard physical education sessions. Long jump performance was evaluated through jump distance and number of successful jumps. Results: The experimental group showed significantly greater improvements in jump distance (males: 29.80%; females: 27.70%) compared to controls (males: 17.30%; females: 16.70%), with a significant Group × Time interaction (P<.001, ηp2 = .46). For successful jumps, the GBG group achieved markedly greater improvements (males: +1.10 jumps; females: +1.40 jumps) versus controls (males: +.60; females: +.50), yielding large effect sizes (Cohen’s d > 1.90) for all comparisons. While females in the experimental group demonstrated a particularly pronounced improvement in successful jumps, no significant sex differences were observed in relative improvements for jump distance. The GBG significantly enhanced both quantitative and qualitative dimensions of long jump performance. Conclusions: These findings extend the established GBG literature beyond behavioural management applications into performance enhancement domains, demonstrating its utility as a powerful pedagogical tool for enhancing targeted motor skills in physical education.

The aim of this study was to analyse physiological and anthropometric characteristics of Croatian national football team players, with particular focus on blood lactate concentration, relative oxygen consumption, body height, body mass, body fat percentage, and playing position. The sample consisted of 17 elite football players. Descriptive statistical analysis was performed for all analysed variables. The average blood lactate concentration was 10.46 ± 1.12 mmol/L, while the average relative oxygen consumption was 60.91 ± 3.15 mL/kg/min. The players demonstrated highly developed aerobic and anaerobic capacities characteristic of elite football populations. Anthropometric and physiological profiles differed according to playing position, reflecting specific tactical and physical demands in modern football.

Background. Selection processes in youth sports often appear to be stressful and unfair to many athletes. One of the reasons also lies in the Relative Age Effect (RAE). This study delves into the phenomenon of RAE in sport, particularly focusing on its potential implications within the realm of kickboxing by exploring its possible occurrence within the Youth Croatian national kickboxing team. Problem and aim. The research aims to shed light on any age-related biases that may exist and their impact on the success and performance of the Croatian national team at the last WAKO World Championships 2022. Material and methods. The research involved 72 youth Croatian kickboxing national team members who were categorized by age and competitive success, with data collected from official sources and analyzed using the Chi-square test. Results. The Croatian youth national kickboxing team does not exhibit RAE based on the obtained results. Despite some uneven quartile distribution, this difference diminishes when considering disciplines and success levels, and the team achieved notable success at the World Championships without the "assistance" of RAE. Conclusion. This article is the first to examine the Relative Age Effect (RAE) in kickboxing. The study found a significant RAE presence in the Croatian national youth team, particularly in the first two quartiles, but further analysis showed no significance in the Semester division. The Croatian kickboxing organisation appears to be aware of RAE and employs fair selection processes, contributing to the team's success, prompting the need for future investigations into RAE at the national and international levels.

Objectives: The study aims to compare three distinct protocols—Moore, Mirwald, and the new BAUSportTM SonicBone system—for predicting somatic maturation in youth athletes. Methods: The participants were female members of the Croatian national volleyball youth team (U-17) (n = 16). The study involved comprehensive measurements, including height, weight, sitting height, leg length, wrist diameter, hand joint diameter, hand grip strength, and ultrasound measurements for skeletal age assessment. Results: Correlation analysis showed moderate to strong correlations between the Moore and Mirwald skeletal age estimates, but both showed weaker correlations with the BAUSportTM skeletal age. Repeated-measures ANOVA showed no significant difference between the Moore and Mirwald methods (p > 0.05); significant differences between both the Moore and Mirwald methods and the BAUSportTM method (p < 0.05). Regression analysis revealed that height, weight, sitting height, leg length, wrist diameter, and hand joint diameter explained 69% of BAUSportTM, with wrist diameter being the only significant predictor. While the Moore and Mirwald methods remain useful tools for estimating the timing of an athlete’s growth spurt, BAUSportTM represents a potential advancement in skeletal age assessment. Further research is needed to validate BAUSportTM across diverse populations and optimize its calibration to accommodate anatomical variations. Conclusions: The findings suggest that with further refinement, BAUSportTM could become a new standard for monitoring skeletal development in youth athletes. Additionally, studies should explore comparative analyses with other emerging technologies, such as genetic markers, hormonal assessments, and MRI, for further understanding of biological maturation in talent identification.

IntroductionThe aim of the TALENT project is to promote equality in education, prevent exclusion, support dual careers (sport and school), create new role models for the benefit of young talents and prepare them for lifelong learning and professional sport from an early age. It is promoted by a European consortium of 7 partner institutions and runs from December 2022 to May 2025. It consists of five work packages. In the first work phase, developing the WP2 (from December 2022 to October 2023), under the coordination of UNIPA, NIS University, KMOP and EAS standards for talent recognition were identified and validated.MethodsInitially, 12 focus groups were conducted with teachers (77 teachers) and coaches (73 coaches) on creating talent identification standards; subsequently, workshops were held with dual career experts to validate these standards. This was a key piece of work that enabled the establishment of clear guidelines and protocols to identify and support talented young people in their dual careers.ResultsA final list of 41 shared statements was identified: 20 related to teachers and 21 related to coaches. For example, teachers emphasized the need for multidisciplinary approaches and early identification of talent, while coaches underlined the importance of psychological readiness and collaboration with schools and families.DiscussionThese statements not only provide structured reference points for talent identification but also highlight actionable needs across educational and sport systems. As such, they represent a solid foundation for developing standard operating procedures in talent recognition and dual career support.

This study aimed to develop predictive equations for unilateral (1-leg) half-squat exercise loads that would elicit equivalent neuromuscular activation, velocity, and force outputs as bilateral (2-leg) half-squat exercise loads. Twelve male soccer players (age 22.9±1.8 y, stature 1.8±0.1 m, and body mass 76.5±6.2 kg) performed both 1-leg and 2-leg half-squats using a Smith-machine. Surface electromyography of vastus lateralis and vastus medialis, barbell velocity and force outputs were measured across incremental loads. Linear regression analyses were conducted to develop predictive equations for 1-leg loads that would match 2-leg exercise outcomes. Three predictive equations were developed: (1) Equivalent muscle activation: 1-leg external load=50% of 2-leg external load –2 kg (r=0.923–0.997, p<0.05). (2) Equivalent barbell velocity: 1-leg external-load=71% of 2-leg external load –17.6 kg (r= –0.916 to 0.994, p<0.05). (3) Equivalent force-output: 1-leg external load=41% of 2-leg external load – 28 kg (r=0.937–0.998, p<0.05). This preliminary investigation provides initial predictive equations for equating unilateral and bilateral half-squat exercises, though validation on independent populations remains necessary. These tools enable practitioners to estimate equivalent loads between exercise modalities using a single one-repetition maximum assessment, facilitating targeted training and rehabilitation program development through accurate load prescription and performance comparisons. Further research is needed to validate these equations on large population and in different sports.

Purpose: This study aimed to investigate the neuromuscular profile of elite youth Taekwondo (TKD) athletes using tensiomyography (TMG) to assess lower-limb muscle contractile properties and estimate muscle fiber composition. Methods: Seventeen members of the Croatian national junior TKD team (10 males, 7 females) participated in this crosssectional study. Anthropometric characteristics and age at peak height velocity (APHV) were assessed, and TMG measurements were performed bilaterally on the vastus lateralis (VL) muscle to obtain contraction time (Tc), delay time (Td), sustain time (Tr), and estimated percentage of type I muscle fibers (MHC-I%). The average chronological age of participants was 16.3 ± 0.9 years, with an average APHV of 13.4 ± 0.7 years. Results: Males were taller and heavier than females, and females showed earlier biological maturation. No significant differences were found between the left and right VL for Tc (21.5 ± 2.6 ms vs. 22.2 ± 2.8 ms; P = .29) or MHC-I% (15.4 ± 9.5% vs. 14.4 ± 11.7%; P = .69). However, a significant side-to-side difference was observed in Td (t = 2.43, P = .03), suggesting asymmetries in neuromuscular activation onset. Substantial intra-individual variability in MHC-I% distribution was also observed. Conclusions: These findings provide novel insight into the contractile characteristics of adolescent TKD athletes and highlight the utility of TMG as a non-invasive profiling tool. The results may inform individualized training design, injury prevention strategies, and athlete development models in youth combat sports. Keywords: talent identification, muscle fiber typology, elite athletes, biological maturation, non-invasive muscle assessment.

This research aimed to propose a new methodological approach for analyzing relative age effect (RAE) in different sports or samples named “Relative age effect overall scale” (RAEOS). The sample consisted of 1455 male and female young athletes who competed in four different sports (basketball, n = 159; handball, n = 215; swimming, n = 981; taekwondo, n = 100) at the Youth Olympic Games (YOG) in Buenos Aires in 2018. To construct the new model, the sample was classified into four unified quartiles of a specific range depending on the sport (swimming: 48-month range, taekwondo: 24-month range, and basketball and handball: 36-month range). Expected and observed frequencies for each sport, the winners/all athletes, and differences between team and individual sports were analyzed using a non-parametric Chi-square test. The obtained results confirm the existence of the RAE in all four analyzed sports (p > 0.01) in a sample of all participants and the sample of gold medalists. Differences between team and individual sports in the analyzed sample have also been found. The proposed methodological approach (RAEOS) is a simple and applicable tool that provides opportunities for comparison and analysis of different sports and competition formats, as well as improvement of the sports talent system in the context of RAE issues. It is suggested to the sports decision-makers to improve the YOG qualification and competition system to enable fairer competition and reduce the influence of RAE on the performance and development of young athletes.

This study examines the maturity status and relative age effect in elite youth taekwondo Croatian National Team athletes. Measurements of biological age, maturity offset, and body composition were taken from a sample of 17 junior athletes. Differences in maturity status were observed among athletes of the same chronological age, with variations in sitting height and age at peak height velocity. Male athletes generally exhibited higher values in body height, percentage of body fat, muscle mass, and total body water. No significant relative age effect was found. These findings highlight the importance of considering individual biological age and maturity status for talent development and training program adjustments. Further research involving athletes from different countries is recommended to validate these results and enhance the understanding of youth taekwondo athlete development.

Purpose: The Relative Age Effect (RAE) and Constituent Year Effect (CYE) is increasingly recognized as a significant concern in youth sports, especially in basketball where physical traits such as height, arm span, and leg length are emphasized. This focus often eclipses the critical role of age-related variations in talent scouting processes. This study aims to explore the presence and impact of CYE in basketball, with a specific focus on the Youth Olympic Games (YOG). Methods: Utilizing statistical analysis, primarily the Chi-square test and Cramer's V, this research examines the occurrence of CYE among basketball players at the YOG. Results: The findings decisively confirm the existence of CYE in youth basketball (P= .000, χ2= 51.593, df= 2, Cramer's V= .403). Results of male (χ2 = 29.342, Cramer's V: .431) and female χ2 =23.43, Cramer's V: .383) also subsample suggest a significant skew in player selection based on birth year, with a large effect size in both cases. A notable discovery is the disproportionate number of athletes born in 2000, who are 19 times more common than those born in 2002, indicating a significant age-related skew in player selection. This indicates a strong association between birth year and player selection in the context of the YOG for both genders. Conclusions: CYE's prevalence in youth basketball could detrimentally impact athletes' development and teams' overall performance. The research emphasizes the need for a more equitable and balanced approach in athlete selection. The paper proposes practical steps to reduce CYE in basketball, such as narrowing age categories or establishing smaller, more precise age groups to ensure fairer competition and more accurate talent identification.

The aim of this study was to determine the factors affecting students’ satisfaction with their class community by measuring the contributions of “positive” resources: either the socio-demographic and individual characteristics of students, or common characteristics of the class community. The research was conducted anonymously using multiple questionnaires on a sample of 267 students attending the higher grades (5th–8th grades) of primary schools from an urban area of the city of Split. It was determined that social cohesion and prosocial behaviour within the class community were the strongest determinants and were also the most important positive resources of satisfaction with the class community. Individual psychological characteristics (especially self-esteem and hope) and the socio-demographic characteristics of students also played a significant role in explaining satisfaction with the class community, but their relative contribution was much weaker than social relations within the class community. The three types of psychological characteristics of the students were positively related to the degree of satisfaction with the class community, but this association was at a low level. More than half of the students were not completely satisfied with their class community. Furthermore, based on the five fundamental dimensions of intrinsic (IM) and extrinsic motivation (EM) within PE motivation, four types of students with different motivational characteristics were determined: the very low type; moderate type; very high IM and low EM type; and extremely high type. It is recommended that experts continue researching the relationship between psychological and social variables in class communities, as well as investigating the effectiveness of possible interventions aimed at the development and improvement of social relationships in the educational and sports talent development environment.

Kickboxing is a relatively young sport with growing popularity across the World. There is a rapidly growing need for clear and valid detailed specific information about the effects of kickboxing as an activity. Therefore, this research aimed to collect all legitimate evidence about the acute and chronic physiological response, as well as monitoring and utilization of specific biomarkers in kickboxing. For this systematic review, the authors conducted research in the three relevant scientific bases and one search engine for this specific topic, PubMed, Web of Science, Scopus, and Google Scholar. After title and abstract screening, and review of full-text manuscripts regarding inclusion criteria, 16 studies were included in the review. Studies were sorted according to the type of research methods used. Results revealed a positive chronic impact of kickboxing on the overall athletes' health, speaking of hormonal, blood, and immune parameters. Although, the acute reaction of athletes' organisms includes the increase in levels of cortisol, growth hormone, testosterone, glucose, indicators of lipid peroxidation activity, H+, BEecf, lactic acid, and pyruvic acid, while the levels of myostatin and irisin tend to decrease. Such results confirm kickboxing as a high-demand anaerobic glycolytic activity. Secondly, the currently available analyses of the greatest value for monitoring in competitive kickboxing are hormonal, especially for testosterone & cortisol, immunoassays & saliva assays for immunity tracking, and genetic analyses as auxiliary tools. Further investigations should include females, kickboxing discipline differentiation, weight and age stratification, and differentiation.

World Taekwondo (WT) as an Olympic sport gained much more attention than before, and there is a growing need for precise and specific profiles of successful taekwondo competitors. Aim of this investigation was to determine body composition, somatotype, and selected anthropometric parameters/indexes of elite taekwondo champions and medal winners on the most demanding taekwondo tournaments in the World. The sample for this research consisted of n=16 (n=4 male; n=12 female) elite taekwondo champions, n=8 juniors and n=8 seniors, who were European (n=13), and World (n=3) champions of European descent. Data was collected longitudinally for seven years since 2015. Obtained results revealed specific (absolute) phenotype of taekwondo champions, following: PI (11.50 female; 11.85 male), HWR (43.96 female; 44.47 male) and BMI (19.96 female; 22.04 male). Further analysis shows that champions have greater values of body height, and have slightly greater ectomorphy and mesomorphy values in regard to other elite competitors. Presented research is the first publication of referent values for the general anthropometric dataset, and such results represent the anthropometric variability of European WT champions.

Heritability estimates for various traits were previously obtained in large-scale twin studies as well as in genomic analyses, which have been used more frequently recently. The potential for heritability in studies of twin athletes has never been observed for tensiomyography (TMG)-derived contractile properties. Accordingly, the aim of this study was to investigate the hereditary capabilities (HC) of lower-limb contractile properties using a twin case study design performed on a pair of monozygotic (MZ) track and field youth champions from Croatia. The results showed high HC values for contraction time, time delay, and contraction velocity, which measure the absolute (Tc, Td) and relative (Vc) velocity of the lower limb muscles. Very high HC values of the listed contractile properties indicate a strong influence of heritability on selected, mainly velocity-related properties, whereas Td-variable related to the peripheral nervous system is the most affected. Second, the muscle morphology of vastus lateralis, vastus medialis, and rectus femoris also appears to be subject to a strong heritable influence. In conclusion, the HC estimates presented, together with the heritability coefficients, can be used as guidelines for talent identification processes, especially when combined with TMG, a suitable non-invasive alternative for estimating lower-limb contractile properties in adolescent athletes.

The aim of this study was to assess the metabolic cost (Cr) with marathon shoes (Adidas Adizero 3 [AA]) vs. track spikes (Nike Zoom Matumbo 3 [NZM]) on track. For this, five experienced runners were randomly assessed (NZM/AA) on a running track at 73% and 85% of best performance speed on 1500-m race. At first, speed (4.39 +/- 0.53 m center dot s(-1)), Crs with AA and NZM resulted 3.63 +/- 0.29 and 3.64 +/- 0.43 J center dot kg(-1)center dot m(-1) (+0.3% with NZM, effect size [ES] small and p = 0.951), respectively. Besides, at second speed (5.20 +/- 0.18 m center dot s(-1)), Crs were 4.09 +/- 0.28 and 4.07 +/- 0.22 J center dot kg(-1)center dot m(-1) (-0.5% with NZM, ES small and p = 0.919) with AA and NZM, respectively. It resulted in an increased Cr (+12.2%) between s1 and s2 with both shoe conditions (ES large and p = 0.009 and 0.011 with AA and NZM, respectively). There is a pattern yet to be confirmed for track spikes to become more beneficial at higher speeds (when duty factor becomes lower and therefore grip on track is crucial).