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Differential responses to seasonal soccer training in U-15 and U-17 players: Body composition, strength, agility, and effect size analysis
Rick Stoop1, Georgios Georgiadis2, Iván González-García31. Football Club Utrecht, Herculesplein 241, 3584 AA Utrecht , NL2. Department of Nutrition and Movement Sciences, NUTRIM School of Nutrition and Translational Research in Metabolism, Maastricht University , NL3. Faculty of Health Sciences, Universidad Isabel I, Burgos , ES2026-06-09|page 48-63AbstractBackground: Training programs during adolescence play a crucial role in optimizing body composition and physical performance in youth soccer players. However, differences in training adaptations between age groups, particularly in agility performance, remain insufficiently explored.
Objectives: This study aimed to examine the effects of a seasonal soccer training program on body composition, strength, and agility in U-15 and U-17 soccer players.
Methods: A pre–post experimental design was applied to 28 male youth soccer players (U-15: n = 15; U-17: n = 13) competing in a football league in the Netherlands. Participants completed a 16-week training program consisting of technical, conditioning, tactical, and mental components. Body composition (height, body mass, lean mass, fat mass), jump performance (SJ, CMJ, CMJmax), isokinetic strength (knee flexion and extension peak torque), and agility (Illinois Agility Test) were assessed before and after the intervention. Data were analyzed using repeated-measures analysis of variance (ANOVA) and effect sizes were calculated using Cohen’s d.
Results: In the U-15 group, significant improvements were observed only in knee flexion (70.2 ± 15.8 vs. 95.4 ± 23.5 Nm, p = 0.006, d = 1.25) and extension peak torque (75.1 ± 20.4 vs. 96.8 ± 18.9 Nm, p = 0.012, d = 1.10). In contrast, U-17 players demonstrated significant increases in lean mass (50.2 ± 3.1% vs. 53.4 ± 2.3%, p = 0.021), reductions in fat mass (11.0 ± 2.9% vs. 8.7 ± 2.5%, p = 0.037), improvements in agility performance (16.2 ± 0.7 vs. 15.4 ± 0.65 s, p = 0.008, d = 1.18), and knee flexion peak torque (78.4 ± 26.5 vs. 118.3 ± 28.7 Nm, p = 0.003, d = 1.45), together with significant gains in jump performance (p < 0.05). Most significant changes in the U-17 group were accompanied by large effect sizes (d = 0.85–1.45).
Conclusions: The training program elicited greater physiological and performance adaptations in U-17 compared to U-15 players. The greater adaptations observed in the U-17 group may be partially influenced by differences in biological maturation; however, maturity status was not directly assessed in the present study.
APA Citation StyleStoop, R. , Georgiadis, G. , & González-García, I. (2026). Differential responses to seasonal soccer training in U-15 and U-17 players: Body composition, strength, agility, and effect size analysis. Sport, Exercise, and Injury, 48-63. https://doi.org/10.56003/sei.v2i1.735 -
Comparative physical fitness profiles of female long-distance and sprint swimmers at Petrokima Gresik Club: A descriptive study
Kartika Jeaniar Fajar Nur Rahma11. State University of Malang , ID2026-01-05|page 90-98AbstractBackground: Physical condition is a fundamental factor that affects swimmers' performance in developing techniques, tactics, and competition strategies, especially for swimmers specializing in different distances, such as sprinters and long-distance swimmers.
Objectives: This study aims to analyze the dominant physical profiles of female sprinters and long-distance swimmers, providing evaluation material for coaches to develop more targeted training programs.
Methods: The study employed a quantitative descriptive design, utilizing a survey and test approach. The research subjects consisted of 20 female swimmers from the Petrokimia Gresik Club who were selected purposively, including 10 sprinters and 10 long-distance swimmers. Data collection was conducted in 2024 through push-up tests (measuring arm muscle strength), sit-ups (assessing abdominal muscle strength), vertical jump (evaluating leg muscle explosive power), and multistage fitness tests (testing aerobic endurance). Raw scores were converted into t-scores and then categorized using the Norm Reference Scale (NRS). Data analysis was performed descriptively using means, standard deviations, and percentages. This study has obtained ethical approval from the relevant ethics committee.
Results: The analysis results show that in the sprinter group, 4 out of 10 athletes (40%) were in the "fair" physical condition category, while in the long-distance group, 5 out of 10 athletes (50%) were also in this category. In general, the components of arm muscle strength, abdominal muscle strength, leg muscle power, and aerobic endurance in both groups showed a relatively balanced distribution with a predominance of the adequate category.
Conclusions: The physical condition of female sprinters and long-distance swimmers from the Petrokimia Gresik Club was at a relatively balanced level, with a predominance of the adequate category. These findings serve as a basis for evaluating and adjusting training programs according to the characteristics of specific swimming specializations.APA Citation StyleRahma, K. J. F. N. (2026). Comparative physical fitness profiles of female long-distance and sprint swimmers at Petrokima Gresik Club: A descriptive study. Sport, Exercise, and Injury, 90-98. https://doi.org/10.56003/sei.v1i2.645 -
Injury trends in Pencak Silat: Impact of regulation changes on sparring athletes
Jhenny Ayu Suryaningrum1, Mohamad Nizam Mohamed Shapie21. State University of Malang , ID2. MARA University of Technology , MY2025-06-17|page 15-26AbstractBackground: Pencak Silat is a martial arts sport with high physical contact intensity, resulting in a high risk of injury. To improve safety and sportsmanship, PERSILAT changed the competition rules in 2017. However, the impact of these changes on athlete injury rates is still debated.
Objectives: This study aimed to compare injury rates between the old and new rules in the sparring category of Pencak Silat athletes.
Methods: The study involved 40 sparring category Pencak Silat athletes in the Greater Malang area, aged 16-25 years, who had experience competing before and after implementing the new rules. Sampling used a purposive sampling technique. Data were collected through an online questionnaire and analyzed descriptively quantitatively with percentage calculations.
Results: The results showed a decrease in injury rates in the new rules compared to the old rules. 50.00% of respondents were injured 1-2 times under the new regulation, lower than 57.50% under the old regulation. The most common injury was bruising (27.06% under the new rules vs. 36.36% under the old rules), while dislocation injuries increased (18.82% vs. 15.58%). The most common injury was to the ankle. Most athletes stated that injuries affected their performance and daily activities.
Conclusions: Rule changes have not eliminated the risk of injury in high-contact sports such as Pencak Silat. A decrease in bruising followed by increased dislocations suggests the need for more specific prevention strategies. This study contributes to understanding the impact of new regulations on athlete safety.
APA Citation StyleSuryaningrum, J. A. , & Shapie, M. N. M. (2025). Injury trends in Pencak Silat: Impact of regulation changes on sparring athletes. Sport, Exercise, and Injury, 15-26. https://doi.org/10.56003/sei.v1i1.511 -
Analysis of dominant physical factors in volleyball skills: confirmatory analysis of the Bahana Muda volleyball team
Mahesa Dwi Chandra11. State University of Malang , ID2026-01-05|page 111-121AbstractBackground: Physical condition is an important determinant of volleyball skill performance, but few studies have empirically tested the structure of its dominant factors using a confirmatory approach.
Objectives: This study aims to identify the dominant physical condition factors that influence the playing skills of Bahana Muda Club volleyball athletes using Confirmatory Factor Analysis (CFA).
Methods: This study used a quantitative descriptive design. The sample consisted of 20 male volleyball athletes from the Bahana Muda Club who were selected through purposive sampling. The physical condition variables measured included speed (30-meter run), endurance (beep test), arm muscle strength (push-ups), abdominal muscle strength (sit-ups), leg muscle power (vertical jump), and agility (shuttle run). The analysis was conducted through an initial exploratory analysis and continued with CFA using IBM SPSS AMOS version 26. The goodness-of-fit model was evaluated using the CFI, TLI, and RMSEA indices.
Results: The CFA results show that leg muscle power (λ = 0.791), arm muscle strength (λ = 0.742), endurance (λ = 0.732), and agility (λ = 0.606) have significant factor loadings on volleyball skills (p < 0.05), while abdominal muscle speed and strength did not show significant contributions. The CFA model showed good data fit (CFI = 0.986; TLI = 0.978; RMSEA = 0.050).
Conclusions: Leg muscle power, arm muscle strength, endurance, and agility are the dominant physical factors in volleyball skills. Training programs should prioritize these components, and further research should involve larger samples and cross-clubs.APA Citation StyleChandra, M. D. (2026). Analysis of dominant physical factors in volleyball skills: confirmatory analysis of the Bahana Muda volleyball team. Sport, Exercise, and Injury, 111-121. https://doi.org/10.56003/sei.v1i2.642 -
Eccentric hamstring strength profile and limb asymmetry in sub-elite female taekwondo athletes: Implications for injury prevention
Christina Septya Dewi1, Pudjijuniarto Pudjijuniarto2, Awang Firmansyah3, Roy Januardi Irawan41. Universitas Negeri Surabaya , ID2. Universitas Negeri Surabaya , ID3. Universitas Negeri Surabaya , ID4. Universitas Negeri Surabaya , ID2025-06-17|page 70-79AbstractBackground: Taekwondo is a physical contact sport requiring quick reactions and explosive movements such as kicking, which depend heavily on hamstring muscle strength to maintain performance and reduce injury risk.
Objectives: This study aims to profile the eccentric hamstring strength and asymmetry in sub-elite female taekwondo athletes in East Java.
Methods: This was a quantitative descriptive study with a cross-sectional approach. A total of 22 female athletes with regional competition experience and no lower limb injuries were selected using purposive sampling. Data were collected using the NordBord by Vald Performance, a reliable tool for measuring eccentric hamstring strength and asymmetry. Descriptive statistics analyzed the mean, standard deviation, minimum, maximum, and strength percentage relative to normative values.
Results: The athletes had an average age of 18.86±2.05 years, body mass of 57.45±8.90 kg, height of 160.68±6.72 cm, and BMI of24.33 ±2.51. Eccentric hamstring strength was 89.6% in the left leg, 85% in the right leg, and 87.2% overall, indicating the need for improvement.
Conclusions: The eccentric hamstring strength of both legs needs to be increased by approximately 12.8% while maintaining the current low asymmetry level to support muscle balance. Targeted hamstring strengthening exercises are recommended to enhance performance and reduce injury risk. This study is limited to female athletes; further research should include broader populations and variables.
APA Citation StyleDewi, C. S. , Pudjijuniarto, P. , Firmansyah, A. , & Irawan, R. J. (2025). Eccentric hamstring strength profile and limb asymmetry in sub-elite female taekwondo athletes: Implications for injury prevention. Sport, Exercise, and Injury, 70-79. https://doi.org/10.56003/sei.v1i1.574 -
Foot biomechanics and injury risk factors in youth football players: A cross-sectional study
Hamza Sinen1, Amirhossein Ghanbarian21. Sintech Prosthesis Orthosis R&D and Innovation Trade Limited Company , TR2. Department of Biomechanics and Sport Injuries , Faculty of Physical Education and Sport Sciences, Kharazmi University, Tehran , IR2026-06-02|page 11-20AbstractBackground: Altered plantar pressure distribution and foot alignment have been suggested in previous studies to be associated with ankle instability and overuse injuries; however, evidence in youth populations remains limited.
Objectives: This study aimed to investigate foot biomechanics and potential injury risk factors in youth football players aged 5–15 years.
Methods: This study employed an analytical cross-sectional design involving 30 youth football players recruited from local football academies. Participants were categorized into three age groups: 5–9 years (n = 10), 10–12 years (n = 10), and 13–15 years (n = 10). Data were collected through pedobarographic plantar pressure assessment, hallux valgus angle (HVA) measurement using a goniometer, navicular drop test (NDT), and subtalar angle assessment. Statistical analyses included descriptive statistics, Shapiro–Wilk normality test, Pearson correlation, independent t-test, and one-way ANOVA with effect size (η²). A significance level of p ≤ 0.05 was applied.
Results: The results showed that hindfoot plantar pressure was higher than forefoot pressure in both feet, indicating a posterior loading pattern. Hallux valgus angles were within normal ranges, while subtalar angles demonstrated a tendency toward pronation. Significant differences were observed in left foot HVA and left hindfoot pressure across age groups (p < 0.05), with moderate effect sizes (η² = 0.20–0.21). Correlation analysis revealed moderate to strong positive relationships between subtalar pronation and HVA variables.
Conclusions: Youth football players exhibit biomechanical characteristics, such as increased hindfoot loading and subtalar pronation, that may represent adaptive responses to sport-specific demands and be associated with potential injury risk. However, given the study's cross-sectional design, these findings should be interpreted as descriptive biomechanical patterns rather than as direct predictors of injury. Early biomechanical screening and targeted preventive training may help support optimal athletic development.
APA Citation StyleSinen, H. , & Ghanbarian, A. (2026). Foot biomechanics and injury risk factors in youth football players: A cross-sectional study. Sport, Exercise, and Injury, 11-20. https://doi.org/10.56003/sei.v2i1.713 -
Injury patterns and risk factors in high school futsal: An observational study
Rafif Jendra Atmaja11. State University of Malang , ID2025-06-17|page 1-14AbstractBackground: Sports injuries at an early age are crucial and must be given attention.
Objectives: This study aims to analyze injury patterns, causative factors, and prevention strategies specific to high school futsal players.
Methods: The research method used was descriptive quantitative with a cross-sectional study approach. The population in this study were male students of State Senior High School 1 Ponorogo who participated in class meeting activities, with purposive sampling technique found 24 samples. Data collected by questionnaire included information on the type of injury, location of injury, causative factors, injury treatment and type of rehabilitation.
Results: The results showed that the most common injuries were cuts/abrasions (29%) and bruises (23%), most common in the lower extremities, namely knees (23%) and ankles (20%), the most common cause of injury was physical contact (54%), most injuries occurred during the second half (67%), the most common first aid given was cold compresses (51%) and the most common rehabilitation/therapy was massage (25%) and physiotherapy (21%).
Conclusions: The findings can be concluded that the most dominant type of injury experienced by students is abrasion, especially in the knee area. In addition, the main causative factors of injury are fatigue, infrastructure, and collisions between players. The results of this study indicate the urgency of implementing injury prevention programs and the importance of conducting post-injury rehabilitation, in an effort to minimize the risk of injury to support the sustainability of students' careers in sports.
APA Citation StyleAtmaja, R. J. (2025). Injury patterns and risk factors in high school futsal: An observational study. Sport, Exercise, and Injury, 1-14. https://doi.org/10.56003/sei.v1i1.513
