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Background Soccer is a dynamic sport that involves high-intensity running, changes of direction, jumping and contact. Therefore, a proper warm-up duration is of great importance to optimize players'performance and minimize the risk of injury. Methods This study examined the responses of amateur young 16 players (age = 17.00 ± 0.81 years; height = 177.38 ± 5.50 cm; weight = 64.50 ± 5.45 kg) 25 min (min), 15 min and 8 min warm-up duration in 4 v 4 small-sided games (SSGs) with mini-goal formats. Participants are assessed using the Participant Classification Framework, they are categorized under Tier 2: Trained/Developmental. The SSG interventions were randomly assigned to three training intervention groups. The features of SSG are determined as size; 25 × 32 m, bout; 4 × 4 min, resting; 4 min. Before the SSG, same protocol was applied at different times in all warm-ups. Warm-up protocols consisted of 13 sections. The intervention time in each section decreased parallel to the total 25 min, 15 min and 8 min warm-up times. The rating of perceived exertion (RPE), heart rate (HR) responses, distance covered and technical activities were consistently recorded during all SSG sessions. A one-way repeated-measures ANOVA was used to assess significant differences in performance among the different warm-up duration. Results After the interventions, HR, total player load (TPL), successful passes (SP), unsuccessful passes (USP), interceptions and lost ball results demonstrated significant difference between the 25-min, 15-min and 8-min warm-up durations ( p < 0.05). Total distance, velocity, RPE and enjoyment results showed no significant difference between the 25-min, 15-min and 8-min warm-up duration ( p > 0.05). Results indicate that a 15-min warm-up duration provides an optimal balance between physiological and technical preparation, leading to improved HR responses, SP and interceptions compared to the 25-min and 8-min warm-ups. The 25-min warm-up decreased USP and lost ball occurrences compared to the 15-min and 8-min warm-ups. The 8-min warm-up resulted in a lower TPL, indicating reduced physiological demands. Conclusions The 15-min warm-up duration emerged as an optimal protocol, offering a time-efficient approach that enhances both technical performance and physiological readiness while avoiding unnecessary fatigue. This finding provides practical implications for coaches and practitioners in designing warm-up routines that maximize match readiness without overexertion.

Objectives This randomized controlled trial compared the effects of velocity-based complex training (VBCT) and traditional complex training (TCT) on lower-limb maximal strength and explosive performance in male volleyball athletes during the competitive season. Methods Thirty athletes were randomly assigned to VBCT ( n  = 10), TCT ( n  = 10), or a control group (CON, n  = 10). The VBCT and TCT groups trained twice weekly for eight weeks. Pre- and post-intervention assessments included 1RM squat, countermovement jump (CMJ), squat jump (SJ), eccentric utilization rate (EUR), and standing long jump (SLJ). Results Both VBCT and TCT improved 1RM squat, CMJ, SJ, and SLJ, whereas only VBCT improved EUR ( p  < 0.01). Post-intervention, VBCT demonstrated significantly greater improvements than TCT in CMJ (VBCT: η² = 0.65; TCT: η² = 0.41) and EUR (VBCT: η² = 0.45; TCT: η² = 0.07) ( p  < 0.05). Training intensity did not differ between groups ( p  > 0.05), but VBCT showed lower training volume, fewer repetitions, and lower rating of perceived exertion, while exhibiting higher mean concentric velocity for each repetition within squat sets compared with TCT ( p  < 0.01). Conclusions VBCT resulted in greater improvements in CMJ and EUR, while its effects on 1RM, SJ, and SLJ were similar to TCT. With lower volume and fatigue, VBCT may be a more efficient strategy for enhancing lower-limb strength and explosiveness during the competitive season. Trial registration This study was registered at the Chinese Clinical Trial Registry ( www.chictr.org.cn ) with the following details: Registration Number: ChiCTR2400093910. Registration Date: 13/12/2024.

Objective The purpose of this study is to systematically review and meta-analyze the effects of in-season flywheel resistance training (FRT) compared to traditional resistance training (TRT) on vertical jump and linear sprint performance in team-sport athletes. Additionally, this study aims to explore the moderating effects of training parameters (such as frequency, intensity, and duration) on training outcomes. Methods This systematic review and meta-analysis followed PRISMA guidelines and was registered in PROSPERO. Five databases were searched for randomized controlled trials comparing in-season flywheel resistance training (FRT) with traditional resistance training (TRT) on vertical jump and sprint performance in team-sport athletes. Risk of bias was assessed using the Cochrane RoB 2 tool, and evidence quality was graded using the GRADE approach. Data were analyzed using Review Manager and Stata, with subgroup and sensitivity analyses performed. Publication bias was evaluated using funnel plots and Egger’s test. Results Seven randomized controlled trials with 199 male athletes were included. The overall risk of bias was moderate, and evidence quality was low. Flywheel resistance training (FRT) significantly improved countermovement jump (CMJ) height (SMD = 0.46, p  < 0.01) and had a small positive effect on linear sprint performance (SMD = -0.38, p  = 0.02). Subgroup analyses indicated that CMJ performance improved with training programs consisting of more than 12 sessions, a duration of 5–10 weeks, and a training frequency of less than twice per week. No significant subgroup effects were observed for sprint performance. Sensitivity analyses confirmed the robustness of the results, and no publication bias was detected. Conclusion Compared with TRT, FRT is more effective in enhancing CMJ performance and linear sprint speeds over specific distances in male team-sport athletes during the in-season. Training protocols characterized by low frequency (≤ 2 sessions per week) and a total of around 12 sessions appear to facilitate better athletic adaptations. Future research should include female athletes and investigate long-term interventions to further refine the application strategies of FRT in in-season training.

Background Soccer performance involves frequent high-intensity efforts and often insufficient recovery, making neuromuscular fatigue a critical factor in player monitoring. The drop jump (DJ) test, particularly the reactive strength index (RSI), has gained attention as a practical tool for assessing neuromuscular readiness. This study examined the relationship between accumulated external training load and neuromuscular status, assessed via DJ-derived metrics, in semi-professional soccer players. Methods Nineteen semi-professional outfield players (20.7 ± 1.4 years) were monitored over a 30-week competitive season, including 144 training sessions and 30 official matches. External load was tracked using 10 Hz Global Positioning System (GPS) devices. Neuromuscular performance was assessed weekly via the DJ test, measuring RSI, contact time (CT), and jump height (JH) with Optojump. Repeated-measures ANOVA evaluated longitudinal changes, and individual correlations were calculated across acute (7-day), chronic (28-day), and acute: chronic workload ratio periods. Results External load metrics varied significantly across microcycles, whereas DJ performance metrics remained stable at the group level. However, individual-level analyses revealed significant associations between external load and DJ-derived metrics (particularly between accelerations, decelerations, and high metabolic load distance with CT and JH) in both acute and chronic windows. Conclusion Neuromuscular responses to external training load appear highly individual among semi-professional soccer players. RSI and its components (CT and JH) should be interpreted separately to enhance decision-making regarding training and recovery. A multi-metric, individualized monitoring approach is recommended to optimize performance and reduce injury risk. Clinical trial number Not applicable.

Background This study aimed to comprehensively and quantitatively evaluate the effectiveness of single-arm acute to chronic workload ratio (ACWR) in predicting sports injuries through an evidence-based approach and to provide references for injury prevention, physical training and training load management. Methods Cohort studies on ACWR were retrieved from PubMed, Web of Science, ScienceDirect, CNKI, and Wanfang, covering the period from the inception of the databases to February 15, 2025. The quality of the included literature was evaluated using the Newcastle-Ottawa Scale (NOS), and a meta-analysis was conducted using Stata (version18.0). Results A total of 22 single-arm cohort studies reporting injury incidence by ACWR category were included. Methodological quality assessment identified 16 high-quality (≥ 7 points) and 6 moderate-quality (4–6 points) indicating an overall high quality of the included research. The results of the Meta subgroup analysis showed that the injury incidence in tissue structures was 79% (95% CI [0.67; 0.89]), the injury incidence in the legs was 73% (95% CI [0.57; 0.86]). Additionally, the injury incidence in soccer players was 75% (95% CI [0.61; 0.87]), the injury incidence due to external loading was 64% (95% CI [0.53; 0.74]), or the injury incidence involving both internal and external loads was 69% (95% CI [0.45; 0.89]), and the injury incidence for individuals over the age of 25 was 73% (95% CI [0.50; 0.91]), whereas the injury incidence was minimized when the interval was kept at 0.8–1.3, with an injury incidence of 56% (95% CI [0.14; 0.94]). Conclusion Although ACWR is associated with sports injury risk and may be useful in injury prevention strategies, it is necessary to use it with caution as a tool for measuring workload. Due to the heterogeneity between studies, potential publication bias, or differences in ACWR calculation methods, these factors may affect the research results. Therefore, future research should be clearer about its practical applicability. Systematic review registration: PROSPERO CRD42024615589.

Background Prior research has suggested links between youth sport special-ization, inter-limb asymmetries, and injury risk, but findings remain inconsistent regarding whether single-sport athletes show greater asymmetries than their multi-sport peers. This study examined differences in inter-limb asymme-try (global, balance, strength) between single- and multi-sport athletes, and explored the prevalence of exceeding clinical thresholds, sex- and sport-specific interactions, and associations with training volume and injury history. Methods A cross-sectional study was conducted on 76 youth athletes (24 single-sport, 52 multi-sport; mean age 12.6 ± 1.7 years) using standardized assessments of dynamic balance (Y-Balance Test) and isometric strength (hand-held dynamometry). Inter-limb asymmetry was calculated using Index-9 in three domains: global asymmetry, balance asymmetry, and strength asymmetry. Differ-ences between single-sport specialists and multi-sport athletes were tested using linear mixed effect models, adjusted for sex, maturity status, BMI, training vol-ume, and sport type. Sensitivity and interaction analyzes (e.g., sport symmetry, sex, injury history) were also performed. Results Inter-limb strength asymmetries greater than 10% were observed in more than half of the participants, especially for ankle plantarflexion and hip abduction. Balance asymmetries were smaller, with fewer than 15% of athletes exceeding the 10% threshold. Training volume was higher in the single-sport group, but was not associated with greater asymmetry. No significant differences were found between single and multisport athletes for global ( β  = 0 . 039, p  =  . 597), balance ( β  = 0 . 037, p  =  . 745) or strength asymmetry ( β  = 0 . 013, p  =  . 879). These null results persisted across the sensitivity analyses and interaction models. Conclusions Despite higher training volumes, single-sport youth athletes did not exhibit greater balance or strength asymmetries than their multi-sport peers. Inter-limb asymmetries were common across the cohort but were not associated with sport specialization. These findings highlight the need for cautious, individ-ualized interpretation of asymmetry measures in youth athletes, and underscore the importance of further research to clarify their developmental and clinical significance. Trial registrations ClinicalTrials.gov (NCT06325228); registered on 10/03/2024.

Background Field test performance is a key indicator of soccer match performance, offering insights into aerobic and anaerobic capacities. This study investigated the relationship between field test performance and match performance in young soccer players. Methods Thirty-eight elite male soccer players (mean ± SD: age 17.1 ± 1.01 years; height 177.17 ± 5.38 cm; body mass 71.18 ± 5.60 kg) participated in the study. Aerobic endurance was evaluated using the Yo-Yo Intermittent Recovery Level 1 test (YIRT1), the 30–15 Intermittent Fitness Test (30-15 IFT ), and the Circular Field Test (FT cir ). Anaerobic capacity was assessed through the Repeated Sprint Test and the 40 m Maximal Running Speed Test (MRS 40 ). Match performance was determined using GPS data, with metrics including total distance covered and distances in different speed zones: walking (0–6.9 km.h −1 ), low-intensity running (7–12.9 km.h −1 ), moderate-intensity running (13–17.9 km.h −1 ), very high-intensity running (18–20.9 km.h −1 ), sprinting (≥ 21 km.h −1 ), and high-intensity actions (≥ 13 km.h −1 ). Results Significant positive correlations were observed between YIRT1 results and total match distance ( r  = .524–.546, p  < 0.01), as well as high-intensity actions ( r  = .490–.518, p  < 0.01). The 30-15 IFT showed moderately positive correlations with total distance ( r  = .401, p  < 0.05) and high-intensity actions ( r  = .455, p  < 0.01). Anaerobic Threshold Running Speed (AnE RS ) demonstrated a weak to moderate relationship with low-intensity running ( r  = -.397 to .312, p  < 0.05). Conclusions In conclusion, among the tests examined, YIRT1 emerged as the most consistent predictor of match-related running performance. While the 30–15 IFT showed a moderate correlation, the relationship with anaerobic tests was limited. These findings highlight the usefulness of YIRT1 in assessing match performance but also reveal that no single test fully reflects the complexity of match performance.

Background This study aimed to explore the quarter-by-quarter variations in external and internal load and their interrelationships throughout basketball games among collegiate basketball players. Methods This longitudinal observational study analyzed data from 18 official games, yielding a total of 470 data points (quarter 1 (Q1): 112, Q2: 128, Q3: 122, Q4: 108) from 14 male players of the Chinese University Basketball Association. Only players without injury records who completed at least 15 min per game and 5 min per quarter in at least five games were included in the final analyses. Catapult S7 devices and Ratings of Perceived Exertion (RPE) were employed to assess both external and internal load variables. Linear mixed-effects models and repeated-measures correlations were utilized to assess differences in external and internal load between backcourt and frontcourt players, as well as to examine the relationship between RPE and objective load metrics across game quarters. Decision tree visualizations were employed to analyze load thresholds and identify key quarter-specific features that differentiate player performance. Results Backcourt players exhibited higher RPE (Q1: p  < 0.01, ES  = 0.72; Q2: p  < 0.001, ES  = 1.3), PlayerLoad (PL)·min − 1 (Q1: p  < 0.001, ES  = 1.0; Q2: p < 0.001, ES  = 1.0), and IMA COD (Q1: p  < 0.05, ES  = 0.69; Q2: p  < 0.01, ES  = 0.67) in the first and second quarters compared to frontcourt players. In contrast, frontcourt players showed increased IMA Accel in the third ( p < 0.01, ES = -0.65) and fourth quarters ( p  < 0.05, ES = -0.90) compared to backcourt players. Additionally, significant correlations were found between RPE and PL (Q1: r  = 0.51, p  < 0.001; Q2: r  = 0.46, p  < 0.001; Q3: r  = 0.57, p < 0.001; Q4: r  = 0.61, p  < 0.01) and explosive efforts (Q1: r  = 0.61, p  < 0.01; Q2: r  = 0.46, p < 0.001; Q3: r  = 0.44, p  < 0.001; Q4: r  = 0.45, p  < 0.01) across all quarters, underscoring the connection between physical exertion and athlete perception. Finally, decision tree with heatmap visualizations identified RPE, PL, and PL·min − 1 as critical feature distinguishing the physical demands of each quarter. Conclusion This study highlights position-specific physical demands across game quarters in basketball, with backcourt players showing higher intensity (RPE, PL·min − 1 , and IMA COD) early in games and frontcourt players exhibiting greater IMA Accel later, supporting tailored training and recovery strategies based on RPE and objective load metrics.

Background Functional performance and physical demands vary by playing position in basketball, with some evidence suggesting differences in speed, agility, and endurance among adolescent athletes. However, the relationship between position-specific roles and measures of trunk stability, balance, and proprioception in female youth players remains underexplored. This study examined the relationships between player positions, trunk stability, and functional performance in adolescent female basketball players. Methods Sixty adolescent female basketball players (28 forwards, 16 centres, 16 guards, mean age = 14.9 ± 1.74 years) were assessed on a 20-metre sprint, 20-metre shuttle run (cardiorespiratory endurance), balance, ankle proprioception, and a modified double-leg lowering task (trunk stability). Differences across playing positions (guard, forward, centre) were analysed using analysis of covariance, controlling for height and weight. Results Cardiorespiratory endurance significantly differed by position ( p  = .011), with centres exhibiting lower maximal oxygen consumption (51.6 ± 4.5 ml/kg/min) than forwards (53.5 ± 4.8 ml/kg/min). Sprint times showed no statistically significant differences, although forwards were slightly faster (3.72 ± 0.20 s) than centres (3.83 ± 0.16 s). No significant differences were observed across positions in trunk stability, balance, or ankle proprioception. Conclusions This study shows that cardiorespiratory endurance is position-dependent in adolescent female basketball players, whereas trunk stability, balance, and ankle proprioception do not vary by position. These findings support the development of targeted training strategies based on playing position and highlight the need for future research to determine whether such functional differences contribute to injury risk or influence performance outcomes, and how early intervention may optimise long-term athlete development.

Background Although it is known that determining the external loads during matches and training is essential for coaches to understand game demands, optimize and specify players’ performance, or avoid overtraining or overload scenarios, it has been observed that the pre-match warm-up external load is neglected. The aims of this study were (i) assess the pre-match warm-up external load for female volleyball players and (ii) compare this load by player position. Methods External loads (total distance, jump count, acceleration (ACC), deceleration (DEC), ACC max , DEC max , ACC/min, speed max , metabolic load) of fourteen elite female volleyball players during pre-match warm-up were monitored with Local Positioning System (LPS) for a season and separated according to player positions (libero (L), outside hitter (OH), opposite (OPP), middle blocker (MB), setter (S)). Results Elite female volleyball players performed 888.1–1078.5 m total distance, 15.9–85.3 jumps (excluding L: 7.6 jumps), 18.5–31.8 ACC and 10.4–28.2 DEC counts, 13.1–15.3 m.sec − 1 speed max and 214.2–406.0 m metabolic load during the pre-match warm-up. While S had significantly higher total distance, jump count, ACC and DEC count, ACC max, ACC/min and speed max (η 2 : large, p  < .001), OH and OPP had the highest metabolic load (η 2 : large, p  < .001). L had significantly higher ACC max and DEC max , speed max data accompanied by significantly lower total distance, ACC count and metabolic load (η 2 : large, p  < .001). Conclusion External load metrics during pre-match warm-up in female volleyball players showed clear positional differences. These findings highlight the need for coaches and strength and conditioning professionals to design role-specific warm-up strategies that reflect the physical demands of each position. By tailoring pre-match preparation in this way, practitioners may better optimize readiness, reduce the risk of fatigue or overload, and improve subsequent match performance.