Anterior cruciate ligament (ACL) injuries commonly occurred through non-contact mechanisms during dynamic tasks such as single-leg landing (SLL). Trunk control and lower limb muscle coordination were believed to play a critical role in modulating knee joint biomechanics and ACL loading; however, their individual muscle contributions remained poorly understood due to the difficulty of in-vivo ACL force measurement. This cross-sectional study aimed to investigate the relationship between core strength, lower limb muscle forces, knee joint biomechanics, and ACL loading during single-leg landing in collegiate athletes. Three-dimensional full-body kinematics, ground reaction forces, and electromyography data were collected and integrated into a musculoskeletal modelling framework to estimate ACL loading and individual muscle force contributions. Findings from this study were expected to provide biomechanical evidence to support targeted injury-prevention and rehabilitation strategies.

Anterior cruciate ligament injuries often led to long-term consequences including early knee osteoarthritis, abnormal neuromuscular function, and reduced athletic participation. Approximately 70% of ACL injuries occurred via non-contact mechanisms, frequently during single-leg landing tasks. During such movements, ACL loading was influenced by joint kinematics, external forces, and neuromuscular coordination of both trunk and lower limb muscles. This study adopted a two-level approach. First, standard biomechanical analyses were conducted to evaluate the relationship between functional core strength and knee joint biomechanics, including knee valgus angle and knee abduction moment during SLL. Second, a musculoskeletal modelling approach was employed to quantify the contribution of individual trunk and lower limb muscles to ACL loading.

Participants performed standardized single-leg landing tasks while wearing inertial motion sensors and surface electromyography electrodes. Ground reaction forces were recorded using a force platform. A full-body musculoskeletal model was scaled to participant anthropometry and used to estimate muscle forces and ACL loading during the landing phase. Statistical analyses included linear regression and linear mixed-effects modelling to examine relationships between muscle forces, knee biomechanics, and ACL loading.

Inclusion Criteria:

• Male collegiate athletes aged 19-25 years
• Minimum of 3 years of competitive experience in jump-landing sports (e.g., volleyball, basketball, netball)
• Training frequency of at least twice per week
• No history of back or lower limb injury

Exclusion Criteria:

• History of major lower limb or back injury requiring surgery
• Any medical condition preventing maximal physical effort
• Current musculoskeletal pain or injury affecting movement performance

The study population consisted of forty collegiate male athletes aged 19 to 25 years who participated in sports involving frequent jumping and landing movements. All participants had a minimum of three years of competitive experience and trained at least twice per week. Individuals with a history of major lower limb or back injury requiring surgery, current musculoskeletal injury, or medical conditions limiting maximal physical effort were excluded. All participants provided written informed consent prior to participation.