Comparison of Plyometric Training Using Differential Learning versus Nonlinear Pedagogy on Functional and Biomechanical Factors in Athletes at High Risk of ACL Injury: Protocol for a parallel-group randomized controlled trial

Background: The incidence of anterior cruciate ligament (ACL) ruptures is notably high among young athletes participating in ball sports. Injury prevention strategies have recently emphasized the integration of multidimensional training with motor learning approaches. Emerging evidence suggests that integrating movement variability effectively reduces modifiable risk factors for ACL injuries. This study aimed to compare the effects of integrating plyometric training with either non-linear pedagogy (NLP) or differential learning (DL) on functional performance and biomechanical risk factors in athletes at high risk of ACL injury. Methods: This single-assessor blind randomized controlled trial will include 48 male athletes (aged 18–26 years) identified as being at high risk for ACL injury. Participants will be randomly allocated to one of three groups: (1) NLP combined with plyometric training (n = 16; 24 intervention sessions over 8 weeks, three sessions per week), (2) DL combined with plyometric training (n = 16; 24 intervention sessions over 8 weeks, three sessions per week), or (3) a control group. outcome assessors will be blinded to their group allocation. The primary outcomes will include kinematic and kinetic variables, while secondary outcomes will assess functional performance. All outcomes will be measured at baseline and following the 8-week intervention period. Discussion: This protocol can be an effective and innovative injury prevention strategy for athletes at high risk of an ACL injury. Designed for practical application in both clinical and field settings, the protocol incorporates plyometric exercises performed under variable conditions. Physiotherapists, athletic trainers, coaches, and return-to-sport specialists can implement it to mitigate the risk of injury. Trial registration: The study was prospectively registered with the Iranian Registry of Clinical Trials (IRCT) on March 15, 2025, under the identifier IRCT20210602051477N3 (https://www.irct.ir/trial/69146).