Extended Abstract
1.    Introduction
The combat readiness and stability of a nation are closely tied to the physical fitness and tactical preparedness of its military forces. Historically, soldiers’ physical conditioning has been a decisive factor in determining battlefield outcomes. Modern military personnel undergo rigorous training programs that include combat drills, endurance running, loaded marches, obstacle navigation, rappelling, climbing, marksmanship, and repetitive jumping—activities that far exceed the physical demands placed on civilian populations (1). While such training enhances operational effectiveness, its repetitive high-intensity nature substantially increases the risk of musculoskeletal injury (2). Military populations consistently report higher musculoskeletal injury rates compared to both general and athletic populations. Epidemiological data indicate 6–12 injuries per 100 soldiers per month during routine training, rising to 30 per 100 during intensive cycles (3). Kerr’s analysis of 3,400 military medical records revealed that 34% of visits were related to musculoskeletal disorders—such as joint pain, muscle strains, and overuse injuries—exceeding trauma-related visits (14%) (4). Among these, lower extremity injuries predominate, with anterior cruciate ligament (ACL) tears being particularly common. Bert’s research reported ACL incidence rates of 3.09 per 1,000 training hours in men and 2.29 per 1,000 in women, significantly higher than rates in civilian cohorts.
The substantial personal and socioeconomic burden of ACL injuries underscores the need to identify and modify risk factors. Biomechanical studies have identified key kinematic predictors of ACL injury, including excessive frontal plane knee valgus/varus, reduced sagittal plane flexion, and increased hip adduction during landing tasks. Cochrane’s work confirms the predictive value of these patterns, highlighting that they are modifiable through targeted neuromuscular and biomechanical training (9).
Accordingly, the present study investigates changes in knee flexion and abduction angles during jump-landing tasks among cadets at Imam Ali (AS) University. These findings are intended to provide essential evidence for the development of injury prevention strategies within military training programs. 
2.    Methods
This longitudinal study included thirty healthy male military cadets from Imam Ali (AS) University (mean age: 19.71 ± 2.30 years; height: 182.66 ± 6.21 cm; weight: 71.83 ± 7.71 kg), all with no history of lower extremity injuries. Participants were evaluated at two time points: the beginning and the end of their first academic year. A standardized jump-landing protocol was employed. Wearing standard athletic shoes, participants stood on a 50 cm platform with feet positioned 35 cm apart (inter-malleolar distance). They were instructed to perform maximal vertical jumps while keeping their hands on their hips and maintaining visual focus on a fixed point at eye level, located two meters away (11). Three anatomical landmarks (greater trochanter, lateral femoral epicondyle, and lateral malleolus) were identified and marked with semi-permanent skin-safe markers. Two Canon cameras were placed 365 cm from the landing area to capture movement in the frontal and sagittal planes at 120 Hz. Each participant completed three trials. Video recordings were analyzed using Kinovea software (version 2.0) to quantify knee flexion and valgus angles at two critical events: (a) initial contact (first frame of visible toe-ground contact) and (b) peak flexion (frame of maximum knee flexion during landing). All measurements were performed by the same investigator to ensure consistency and reliability.
The testing protocol simulated natural landing surfaces rather than force plate instrumentation, with consistent camera positioning and marker placement across both sessions (12). For statistical analysis, a two-way repeated measures ANOVA (time: pre vs. post × limb: dominant vs. non-dominant) was conducted using SPSS version 25. Statistical significance was set at p < 0.05, and effect sizes were reported as partial eta-squared. Normality assumptions were confirmed using the Shapiro–Wilk test.
3.    Results
Key findings indicated marked biomechanical changes in the dominant limb. Knee flexion angle at peak flexion decreased significantly from 96.26° ± 8.41° to 87.27° ± 6.92° (p = 0.028, η² = 0.18), while knee valgus angle increased from 12.32° ± 3.24° to 17.44° ± 4.07° (p = 0.007, η² = 0.21).
In contrast, the non-dominant limb exhibited less pronounced changes (flexion: 93.50° ± 9.31° to 89.48° ± 8.09°; valgus: 13.95° ± 2.77° to 15.48° ± 3.22°). A significant time × limb interaction was observed (F(1,30) = 5.12, p = 0.028), confirming the development of bilateral asymmetries. Detailed descriptive and inferential statistics are presented in Tables 1 and 2. 

 

4.    Discussion
Military training programs should prioritize injury prevention by incorporating targeted movement education alongside physical conditioning. The observed biomechanical adaptations during high-impact activities highlight the need for systematic modifications to current training approaches. Three essential components should be integrated into standard military training: First, movement technique training must emphasize proper landing mechanics, ensuring soldiers develop safe movement patterns from the outset. Second, balance and proprioceptive exercises should be routinely implemented to enhance joint stability and neuromuscular control. Third, training programs should address bilateral asymmetries through unilateral strengthening protocols. These evidence-based recommendations aim to preserve operational readiness while reducing preventable musculoskeletal injuries. Implementing such preventive strategies would represent a proactive approach to soldier health, potentially decreasing medical attrition rates and maintaining force effectiveness. Future training protocols should consider periodic biomechanical assessments to monitor at-risk individuals and evaluate intervention effectiveness. 

Ethical Considerations
Compliance with ethical guidelines
This study was conducted in accordance with the 2013 Helsinki Declaration. Participants provided informed consent after being informed of the research objectives. 
Funding
This research did not receive any financial support from government, private, or non-profit organizations. 
Authors' contributions
All authors contributed equally to preparing the article.
Conflicts of interest
The authors of this article declare no conflicts of interest that could influence the results or interpretation of the findings in this research.