Background and Purpose
Lower limb injuries are common among soccer players, especially in youth categories, and can significantly affect performance, career longevity, and overall health. The most frequent injuries involve the knee, ankle, and hamstring muscles, often caused by improper landing, sudden directional changes, limited knee and trunk flexion, and poor neuromuscular control. Since biomechanical and movement factors play a central role in these injuries, identifying related risk factors and analyzing biomechanical parameters during key soccer movements such as jump landing and cutting maneuvers is crucial. Accordingly, this study aimed to identify lower limb injury risk factors among players of the Iran National Youth Soccer Team and to analyze biomechanical characteristics associated with injury risk. The findings are intended to provide scientific insights for improving movement mechanics, enhancing performance, and preventing injuries among youth soccer players.
 
Methods
This descriptive–comparative study was conducted on 25 male players from the Iran National Youth Football Team, all of whom competed at the highest national level. Following coordination with the national IFMARC center, demographic data including age, height, weight, and body mass index (BMI) were collected. To assess lower limb functional and biomechanical characteristics, three field-based performance tests were administered: the Weight-Bearing Lunge Test (WBLT), the Football-Specific Jump-Landing Test, and the Cutting Movement Assessment Score (CMAS) test at 70° and 90° cutting angles. The WBLT was used to measure ankle dorsiflexion range of motion (ROM) for both left and right limbs using an angular-based calculation method. During the jump-landing test, each participant performed a vertical jump and landed first bilaterally and then unilaterally, while the kinematic variables including knee flexion, ankle dorsiflexion, trunk flexion, knee valgus, and lateral trunk lean were analyzed. In the CMAS protocol, cutting maneuvers to both sides were evaluated to detect biomechanical errors such as internal hip rotation, knee valgus, limited knee flexion, trunk misalignment, and insufficient deceleration strategy. All trials were recorded with two high-speed cameras operating at 250 frames per second, and movement data were analyzed using Kinovea motion analysis software. Statistical analysis was performed in SPSS version 27, employing paired t-tests to compare conditions, with a significance level set at p < 0.05.
 
Results
The results showed that the participants had a mean age of 18.40 ± 0.50 years, a mean height of 182.24 ± 6.70 cm, a mean weight of 75.24 ± 6.63 kg, and a mean BMI of 22.63 ± 1.00. The WBLT results revealed no significant difference in ankle dorsiflexion ROM between the left (47.37 ± 4.16°) and right (47.36 ± 2.75°) limbs, suggesting symmetrical ankle mobility. However, the football-specific jump-landing test indicated significant differences between single-leg and double-leg landings in knee flexion, trunk flexion, and ankle dorsiflexion (p < 0.05). Both knee and trunk flexion angles were substantially lower during single-leg landings than during double-leg landings, reflecting a decreased capacity for shock absorption under single-limb conditions. Furthermore, lateral trunk lean was significantly greater during single-leg landings, indicating weaker trunk stability and control, which may predispose players to increased loading on the lower limb joints.
In the CMAS test, players were assessed in four cutting conditions (left and right directions at 70° and 90° angles). More than half of the participants were classified as being at a moderate level of injury risk, with smaller percentages categorized as high-risk or low-risk. Specifically, in the 90° right cutting maneuver, 56% of the players were in the moderate-risk group and 16% in the high-risk group, while in the 70° right cutting, 60% were moderate-risk and 8% high-risk. Comparable trends were observed for the left-side maneuvers. Detailed kinematic assessments showed that many players exhibited initial internal hip rotation, knee valgus, and restricted knee flexion during cutting, particularly at the 90° angle, which are recognized as key contributors to anterior cruciate ligament (ACL) injury risk. Qualitative video analysis further revealed that most players failed to employ proper deceleration strategies during cutting maneuvers, resulting in elevated shear forces at the knee and increased ground reaction forces. Additionally, the trunk was frequently observed to remain neutral or internally rotated in the frontal plane, a pattern that amplifies valgus torque and destabilizes the knee joint. Players who demonstrated reduced knee, trunk, and ankle flexion—combined with increased valgus and lateral trunk inclination—were identified as being at a higher risk of lower limb injury.
 
Conclusion                                                                                                      
These findings highlight the importance of proper landing and cutting mechanics in preventing lower limb injuries among young soccer players. Reduced knee and trunk flexion, limited ankle dorsiflexion, and poor neuromuscular trunk control increase stress on the knee, particularly the ACL, and compromise dynamic balance and stability. Increased lateral trunk lean during single-leg movements further indicates deficiencies in neuromuscular control. The study revealed that players of the Iran National Youth Soccer Team exhibited movement patterns placing them at moderate to high risk of lower limb injuries, with primary risk factors including reduced knee and trunk flexion, dynamic knee valgus, limited ankle dorsiflexion, and impaired trunk control. These results emphasize the need for specialized training programs targeting trunk stability, proper landing techniques, ankle mobility, and cutting maneuvers. Field-based screening tools such as CMAS and soccer-specific jump-landing tests can identify at-risk players and monitor improvements. Integrating neuromuscular training in youth development may reduce injuries and enhance performance, warranting further experimental research.
 
Article Message
Proper landing and cutting mechanics are crucial for preventing lower limb injuries in youth soccer players. This study on the Iran National Youth Soccer Team identified key risk factors, including reduced knee and trunk flexion, limited ankle dorsiflexion, dynamic knee valgus, and poor trunk neuromuscular control. Findings emphasize the need for targeted training programs focusing on trunk stability, ankle mobility, and proper landing and cutting techniques. Field based assessments such as CMAS and soccer specific jump-landing tests can effectively identify at risk players and monitor improvements, supporting injury prevention and performance enhancement in young soccer athletes.
Ethical Considerations
The present study was derived from a research plan approved (No: 4503001/1/7) by the Faculty of Sport and Health Sciences, University of Tehran, and was approved by the Ethics Committee of the University of Tehran with the ethics code number IR.UT.SPORT.REC.1404.067.
Authors’ Contributions
The authors of the present study have contributed equally to the review and writing process of the article.
Conflict of Interest
The research conducted does not have any conflict of interest.
 
Acknowledgments
The authors of this study sincerely thank the participating athletes and support personnel of the Iranian National Youth Soccer team who facilitated this research.