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

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 | Research Square window.SnipcartSettings = { analytics: { enabled: false } }; (function() { var accessVector = localStorage.getItem('access_vector') || ''; window.dataLayer = window.dataLayer || []; if (accessVector) { window.dataLayer.push({ user: { profile: { profileInfo: { snid: accessVector } } } }); } })(); (function(w,d,s,l,i){w[l]=w[l]||[];w[l].push({'gtm.start':new Date().getTime(),event:'gtm.js'});var f=d.getElementsByTagName(s)[0],j=d.createElement(s),dl=l!='dataLayer'?'&l='+l:'';j.async=true;j.src='https://www.googletagmanager.com/gtm.js?id='+i+dl;f.parentNode.insertBefore(j,f);})(window,document,'script','dataLayer','GTM-K279D39R'); Browse Preprints In Review Journals COVID-19 Preprints AJE Video Bytes Research Tools Research Promotion AJE Professional Editing AJE Rubriq About Preprint Platform In Review Editorial Policies Our Team Advisory Board Help Center Sign In Submit a Preprint Cite Share Download PDF Research Article 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trial Majid Hamoongard, Malihe Hadadnezhad, Hassan Sadeghi, Mehdi Khaleghi Tazji, and 1 more This is a preprint; it has not been peer reviewed by a journal. https://doi.org/ 10.21203/rs.3.rs-7114294/v1 This work is licensed under a CC BY 4.0 License Status: Published Journal Publication published 17 Feb, 2026 Read the published version in Trials → Version 1 posted 5 You are reading this latest preprint version Abstract 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). ACL injury risk research Plyometric training Motor learning strategy Ecological constraints Nonlinear dynamics Figures Figure 1 Administrative information Note: the numbers in curly brackets in this protocol refer to SPIRIT checklist item numbers. The order of the items has been modified to group similar items (see http://www.equator-network.org/reporting-guidelines/spirit-2013-statement-defining-standard-protocol-itemsfor- clinical-trials/). Title {1} 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 Trial registration {2a and 2b}. IRCT20210602051477N3 (https://www.irct.ir/trial/69146) Protocol version {3} Version 5 of 2025-03-15 Funding {4} The authors declare that they did not receive any funding from public, commercial, or nonprofit agencies to conduct this research. Author details {5a} Majid Hamoongard (Corresponding author), Faculty of Physical Education and Sports Sciences, Kharazmi University, Tehran, Iran. Malihe Hadadnezhad, Faculty of Physical Education and Sports Sciences, Kharazmi University, Tehran, Iran. Hassan Sadeghi, Faculty of Physical Education and Sports Sciences, Kharazmi University, Tehran, Iran. Mehdi Khaleghi Tazji, Faculty of Physical Education and Sports Sciences, Kharazmi University, Tehran, Iran. Anne Benjaminse, Department of Human Movement Sciences, University Medical Center Groningen, University of Groningen, Netherlands. Name and contact information for the trial sponsor {5b} Kharazmi University, Tehran, Iran. Address: Kharazmi University No.43 South Mofateh St Tehran, 15719-14911 Iran. Telephone: +98 (21) 88329220. Email: [email protected] . Role of sponsor {5c} No roles in the collection, management, analysis, and interpretation of the data; writing of the report; or the decision to submit the report for publication. Introduction Background and rationale {6a} Anterior cruciate ligament (ACL) injuries are complex, challenging, and multi-factorial, and they are most commonly seen in football, volleyball, handball, and basketball [ 1 ]. ACL tears are among the most prevalent traumatic knee injuries in sports [ 2 ]. Despite advances in research and the adoption of injury prevention programs, the rate of these injuries has increased twofold over the past two decades [ 3 ]. ACL ruptures occur during dynamic activities that require high knee loading, such as single-leg landing after a jump [ 4 ]. Competitive and recreational athletes are at the highest risk of injury [ 1 ]. Among young athletes, the risk of sustaining a secondary ACL injury within two to five years after the initial injury has been reported to range from 25–35% [ 5 ]. ACL tear can be a debilitating and life-changing injury that can result in a long rehabilitation period for athletes, difficulty returning to pre-injury performance levels, and significant healing complications [ 2 , 6 ]. This injury can increase the risk of cartilage damage and osteoarthritis [ 7 ]. Given these long-term consequences, prevention and risk reduction programs for ACL injuries should be a high priority [ 2 ]. Injury prevention programs typically integrate a combination of plyometric, resistance, balance, and technique training, all of which are designed to promote neuromuscular adaptations [ 6 ]. Specifically, plyometric training has been shown to mitigate ACL injury risk by facilitating the retraining of proper movement techniques and body mechanics [ 1 ]. Plyometric training is widely used to improve athletes' rate of force development and explosive power, as it enhances neuromuscular function and motor control [ 8 ]. A meta-analytic review reported that injury prevention programs incorporating plyometric training were associated with a 60% reduction in injury risk per 1,000 hours of training and competition [ 9 ]. Team sport performance is shaped by both physical and cognitive abilities, such as decision-making, anticipation, and rapid information processing, essential for adapting to dynamic game demands [ 10 ]. Variability in playing conditions emerges from a range of constraints associated with the athlete, the task, and the environment [ 11 ]. In sports, athletes routinely perform complex movements under diverse constraints, including varied body positions, the presence of opponents, and limited time for decision-making and execution [ 12 ]. Nevertheless, the majority of functional performance tests employed to assess and prepare injured athletes for return to sport do not adequately reflect the complexity and ecological validity of competitive environments [ 2 ]. This emphasizes the need for more ecologically valid and sport-specific tests that more accurately reflect the multifaceted demands of athletic performance [ 12 ]. Task constraints may include the athlete's goal and any rules or factors that determine or limit the dynamics of the athlete's response (such as a defender blocking the athlete's path) [ 10 ]. Environmental constraints may include characteristics such as terrain type and weather conditions [ 2 ]. Athlete-related constraints include intrinsic factors such as physical and psychological attributes, including anthropometric measurements, attentional capacity, motivational states, and anxiety levels [ 13 ]. These constraints act as boundary conditions that modulate and guide an athlete's self-organized movement patterns in dynamic performance environments [ 11 ]. The influence of various constraints is mediated by the athlete’s capacity to perceive and interpret them [ 14 ]. Since sports environments are unpredictable, rehabilitation must be adaptable, enabling athletes to adjust to shifting demands based on their perceptual-cognitive abilities [ 10 ]. Previous research has shown that training programs integrating neurocognitive strategies are more effective at reducing the risk of ACL injury than programs focusing exclusively on neuromuscular control [ 4 , 7 , 15 ]. Reviews indicate that variability-based training outperforms other cognitive methods in enhancing biomechanical factors linked to ACL injury risk [ 7 ]. The traditional motor-learning paradigm prioritizes repetitive practice aimed at maintaining an "ideal" movement pattern [ 16 ]. In contrast, the ecological dynamics framework posits that no movement is ever reproduced identically in authentic sporting contexts; each action is uniquely shaped by the interaction of individual, task, and environmental constraints at each moment [ 17 ]. While movement variability was traditionally viewed as error or noise, current evidence indicates that regulated variability enhances performance adaptability, self-organization process, and mitigates injury risk [ 18 ]. Within the ecological dynamic framework, motor learning emerges from the continuous interaction of the individual, task, and environmental constraints [ 19 ]. These constraints are conceptualized as boundaries that shape and guide the emergence of behavior [ 20 ]. This dynamic interplay compels learners to explore and stabilize functional, effective movement patterns during goal-directed activities [ 17 ]. A key challenge in applying variability to training is fostering exploratory behavior [ 13 ]. Exposing athletes to exploratory performance conditions or increasing variability in training protocols may allow them to develop new motor skills and capabilities [ 21 ]. Practice variability enhances motor learning by promoting skill generalization, fostering self-organization, enabling optimal movement discovery, encouraging exploration, and improving cognitive flexibility [ 22 ]. Reduced movement variability may hinder learners' ability to adapt flexibly to task-specific constraints and dynamically changing environments [ 23 ]. The theory of optimal movement variability posits that therapeutic interventions should avoid enforcing a single 'ideal' movement pattern [ 24 ]. Instead, programs should target functional limitations by maintaining variability within an optimal range, thereby enhancing adaptability and performance [ 13 ]. Nonlinear pedagogy (NLP) and differential learning (DL) approaches are based on the idea that movement variability comes from the way multiple constraints interact [ 18 ]. In particular, DL promotes exposure to a wide range of movement patterns, facilitating the exploration of diverse motor solutions and enhancing adaptability [ 25 ]. The DL exercises promote engagement with diverse movement patterns rather than avoidance of variability, fostering motor learning and adaptability through exploratory behavior [ 26 ]. The NLP approach emphasizes acquiring motor skills through exploratory behavior and developing individualized movement solutions [ 16 ]. The principal aim of NLP is to improve adaptability through structured variability during practice, achieved by systematically manipulating task and environmental constraints to evoke context-dependent motor responses [ 23 ]. The DL approach has consistently demonstrated efficacy in optimizing ACL-protective biomechanics and functional performance, outperforming conventional motor learning paradigms in comparative studies [ 16 , 27 , 28 ]. Preliminary evidence suggests the NLP approach may improve specific biomechanical factors more effectively than DL, though current findings remain inconclusive and require further validation [ 16 , 18 ]. A comprehensive literature review revealed no existing studies directly comparing DL and NLP approaches for improving biomechanical and functional factors in high-risk ACL athletes. Justification for the study Objectives {7} Primary aim The primary aim of this study is to compare the effects of plyometric training using DL versus NLP on biomechanical factors in athletes at high risk of ACL injury. Secondary aim The secondary aim of this study is to compare the effects of plyometric training using DL versus NLP on functional performance in athletes at high risk of ACL injury. PICO question Can variability-based training approaches, specifically NLP and DL integrated with plyometric training, enhance functional performance and landing biomechanics in athletes at high risk of ACL injury, relative to a control group? Study hypothesis We hypothesize that both DL and NLP will outperform the control, with potential differences between them. Trial design {8} This study is a three-arm, single-assessor blind, randomized controlled trial employing a parallel-group design to be conducted among male athletes at high risk for ACL injury. Participants will be randomly allocated in a 1:1:1 ratio to one of three groups: NLP, DL, and control. The superiority framework will guide the statistical analysis, with the null hypothesis (H0) being that there is no significant difference between the intervention and control groups, and the alternative hypothesis (H1) being that the intervention group demonstrates superior outcomes. This study received ethical approval from the biomedical research ethics committee of Kharazmi University (Approval Code: IR.KHU.REC.1403.169). Furthermore, the trial was prospectively registered in the Iranian registry of clinical trials (IRCT) under the registration code: IRCT20210602051477N3. The protocol conforms to established international reporting guidelines, including SPIRIT, CONSORT, and TIDieR [ 29 – 31 ]. The study flowchart is illustrated in Table 1 and Fig. 1 . Table 1 Recommended protocol items scheduled for enrolment, interventions, and assessments according to evidence [ 29 ] ENROLMENT ALLOCATION BASELINE AFTER 8 WEEKS TIMEPOINT -t 1 0 Pr 1 Po 1 ENROLMENT : Eligibility screen X Informed consent X [Randomization] X Allocation X INTERVENTIONS : NLP plus plyometric training X DL plus plyometric training X Control X ASSESSMENTS Trunk flexion X X Trunk lateral flexion X X Knee flexion X X Knee abduction X X Hip flexion X X Hip adduction X X Hip internal rotation X X Ankle dorsiflexion X X Ground reaction force X X Knee flexion moment X X Knee abduction moment X X Hip abduction moment X X Hip external rotation moment X X Tuck jump test X X X SLTCH X X 90MRH X X SLMTH X X Pr 1 : Pre-test, Po 1 : Post-test, SLTCH: Single-leg triple crossover hop for distance test, 90MRH: The 90 medial rotation hop for distance test, SLMTH: Single-leg medial side triple hop for distance test. Methods Participants, interventions, and outcomes Study setting {9} McKinney et al. define competitive athletes as individuals training > 6 hours weekly with performance-focused objectives and regular participation in organized competitions (e.g., collegiate sports) [ 32 ]. Participants will include 16 male athletes per group (ages 18–26) from Tehran universities, actively competing in elite futsal, volleyball, handball, or basketball programs. The focus on male athletes was justified by their elevated ACL injury risk, understudied prevention programs, and practical recruitment advantages [ 33 ]. This study will include two intervention groups, one using DL and the other using NLP, as well as a control group. Data were collected at two time points: baseline (pre-intervention) and post-intervention (following eight weeks). Before the pre-test, participants will complete a standardized warm-up consisting of two sets of eight bilateral squat repetitions, two sets of five bilateral jump squat repetitions, and dynamic calf muscle stretching exercises [ 28 ]. Eligibility criteria {10} The inclusion criteria will be: male collegiate athletes aged 18–26 years competing in futsal, basketball, volleyball, and handball [ 27 ], body mass index (BMI) ranges from 18.5 to 25 kg/m 2 [ 34 ], tuck jump test score ≥ 6 [ 35 , 36 ], no observable spinal or lower limb malalignments per clinical examination [ 37 ], no history of musculoskeletal injury within the past year that would have resulted in extended absence from athletic participation [ 37 ], no history of ACL injury, and no medical history of neurocognitive, metabolic, auditory, or visual impairments[ 34 , 38 ], and no history of concussion-related symptoms, such as recurrent headaches or migraines, oculomotor deficits, or balance disorders, within the past five years [ 38 ]. The exclusion criteria will be: recent injury prevention program participation (past year) and inadequate attendance (> 2 consecutive or > 3 total absences) [ 39 ]. Who will take informed consent? {26a} The investigator (M.H.) will obtain written informed consent from all participants after providing a clear explanation of the potential benefits and risks of participation, as well as informing them of their right to withdraw from the study at any time. The researchers conducted this study following the principles outlined in the Declaration of Helsinki. Before enrollment, all participants will receive complete written and verbal disclosure of study procedures, potential benefits, and foreseeable risks. All data were anonymized and stored securely with access limited to the research team. Additional consent provisions for the collection and use of participant data and biological specimens {26b} The informed consent document outlines the specific tests to be conducted and states that the data collected will not be reused beyond the scope of this study. As the study does not involve the collection or use of biological specimens from participants, no additional consent will be required. Interventions Explanation for the choice of comparators {6b} Emerging motor learning paradigms that prioritize movement variability appear more effective than neurocognitive-focused interventions in enhancing biomechanical factors associated with ACL injury prevention [ 7 ]. While the superiority of NLP over DL has been attributed to factors such as cognitive flexibility, self-organization, and exploratory capabilities, this conclusion is primarily grounded in theoretical discussions rather than empirical evidence [ 18 ]. No empirical studies to date have evaluated the relative efficacy of DL and NLP paradigms in modifying biomechanical risk factors and functional performance among athletes at high risk of ACL injury. Intervention description {11a} Plyometric training program Plyometric-based injury prevention programs have demonstrated effectiveness in reducing injury risk and improving biomechanical factors associated with ACL injury [ 9 ]. The intervention will span eight weeks, comprising three sessions per week, each lasting 60 minutes, for a total of 24 training sessions. The protocol is structured into three progressive phases: technical, fundamental, and functional. The aim of the technical phase (weeks 1 and 2) is to enhance motor control and to develop correct jumping and landing techniques. This phase focuses on instructing participants in proper posture and joint alignment, and achieving soft landings. All exercises during this phase will be performed bilaterally. The fundamental phase (weeks 3 to 5) aims to enhance power, strength, and agility by progressively increasing the intensity and duration of the training sessions. During this phase, single-leg landings are introduced. The final stage, the performance phase (weeks 6 to 8), is designed to optimize athletic performance, with a focus on maximizing vertical and horizontal jump height and improving landing mechanics. A rest interval of one to two minutes will be provided between each exercise to allow for adequate recovery [ 40 ] (Table 2 ). Table 2 Plyometric training program [ 40 ] Phase I—Technique (1–2 wk) Phase II—Fundamental (3–5 wk) Phase III—Performance (6–8 wk) 1. Wall jumps: 20 s 2. Squat jumps: 15 s 3. Lunge jumps: 15 s 4. Horizontal jump: 8 reps 5. 180-degree jumps: 20 s 6. Forward–backward jumps over the line: 20 s 7. Jump over barriers: 8 reps 8. Lateral–medial jumps over the line: 20 s 9. Lateral jump over the line + vertical jump: 8 reps 10. Drop landing: 8 reps 1. Vertical hop + athletic position in single-leg standing: 10 reps 2. Wall jumps: 30 s 3. Squat jumps: 2×15 4. Triple horizontal jump + vertical jump: 6 reps 5. 180-degree jumps: 15 s 6. Lunge jumps: 15 s 7. Jump over barrier + jump to platform: 6 reps 8. Lateral-medial jumps over barrier: 2×15 9. Forward-backward jumps over barrier: 2×15 10. Anterior drop jump + maximum vertical jump: 6 reps 11. Lateral drop jump + maximum vertical jump: 6 reps 1. Vertical hop + athletic position in single-leg standing: 10 reps 2. Tuck jumps: 15 s 3. 180-degree horizontal jumps: 20 s 4. Lunge jumps with trunk rotation: 20 s 5. Maximum horizontal jump + maximum vertical jump: 6 reps 6. Forward–backward hops over the line: 15s 7. Lateral–medial hops over the line: 15 s 8. Horizontal hop: 4 reps 9. Lateral drop landing + maximum vertical jump + maximum horizontal jump: 6 reps 10. Horizontal hop over barriers + hop to Platform: 4 reps 11. Lateral and medial hop over barriers + hop to platform: 8 reps 12. Single-leg drop landing + maximum vertical hop: 4 reps Nonlinear pedagogy (NLP) This approach does not involve providing explicit instructions or feedback on executing an ideal movement pattern (in contrast to DL). Instead, it encourages participants to engage in self-directed exploration of movement solutions by manipulating task and environmental constraints. Through repeated practice under consistent constraints, individuals can discover a range of movement strategies, fostering the development of adaptive and individualized solutions [ 22 ]. Upon successful attainment of the desired outcome by participants, task constraints and environmental conditions are systematically modified to correspond with individual capabilities, thereby introducing novel challenges and fostering ongoing adaptation. Task and environmental constraints will be individually tailored based on each participant's specific tasks, skill level, and personal characteristics. However, instructors are not permitted to provide guidance or instruction on how the movement should be performed. In general, this approach is characterized by variability in practice conditions, with learners encouraged to explore individualized movement solutions within the given constraints. The task goal is clearly defined, repetition is permitted, but no external feedback or instructional cues are provided [ 16 , 23 , 41 ]. Table 3 and additional file 1. Table 3 Key characteristics of the differential learning and non-linear pedagogy strategies [ 23 ] Group NLP DL Target The task goal was clear, and it was important to achieve it. The task goal may be absent, but how the action was executed was important. Pattern No ideal pattern was prescribed; instead, participants generated individualized movement solutions based on their unique characteristics, task demands, and environmental constraints. Numerous prescribed patterns were provided, and participants adhered to them. Description While the task goal was clearly defined, specific movement patterns were not described. Each movement pattern and task goal were described. Prescription Prescription was not allowed. Prescription was encouraged. Repeat Repetition was allowed. Repetition was not allowed. Variability Unstructured movement variability was promoted through systematic manipulation of task and environmental constraints, directing participants' attention toward discovering adaptive movement solutions. variability was encouraged by prescribing different movement patterns, and also manipulations of task and environmental constraints were allowed. Participants attended to the prescribed motor pattern. Feedback Feedback was not allowed. Feedback was not allowed. Instructions Instructions were allowed (to manipulate task constraints). Instructions were encouraged (to prescribe always differing movement patterns). Differential learning (DL) Participants are not required to replicate identical movement patterns; each movement is executed in varied forms, and no feedback is provided during performance. The required movement patterns are introduced verbally before each exercise. Consequently, each exercise is performed in a novel manner without direct repetition, relying on the instructor's creativity to generate diverse movement variations[ 42 ]. The progression of each exercise is based on repetition without repetition, from simple to advanced interventions. In general, in this approach; the goal of the task may not exist but the way it is performed is important, there are varied movement patterns, movement patterns are prescribed in advance, repetition is not allowed, there is random variability and manipulation of the task and environment constraints is allowed, feedback is not allowed but varied movement instructions are prescribed [ 16 ]. Table 3 and additional file 1. Criteria for discontinuing or modifying allocated interventions {11b} The trial may be discontinued at the request of any participating subject if pain or injury occurs during the interventions. Strategies to improve adherence to intervention protocols {11c} To enhance adherence, weekly phone calls will be conducted to monitor each participant’s progress and gather feedback regarding any challenges encountered during the intervention. Additionally, motivational strategies will be employed, and participants will be informed of the potential benefits of the exercise program to further promote engagement and compliance. Exercise fidelity is a key measure of adherence and refers to athletes performing exercises with proper biomechanics, intensity, and completion of prescribed sets and repetitions [ 43 ]. Therefore, a fidelity checklist will be developed for trainers to monitor adherence, exercise execution, and compliance with prescribed frequency, intensity, time, and type (FITT) of exercises. Additional file 2 Relevant concomitant care permitted or prohibited during the trial {11d} Participants will be asked to maintain a regular diet and adequate rest, and to refrain from smoking, tobacco, medication, caffeine, and alcohol for 24 hours prior to testing. Provisions for post‑trial care {30} The protocol poses no additional risks to participants beyond those inherent to general sporting activities, as it comprises controlled exercises and excludes the implementation of hazardous interventions. Trainers with recognized qualifications in injury prevention training will oversee the implementation of the training protocols and the management of potential confounding factors. Outcomes {12} Primary outcome measures Consistent evidence from multidimensional biomechanical analyses identifies three key ACL injury risk profiles. Including reduced sagittal-plane joint loading (decreased hip/knee flexion angles and moments), excessive frontal-plane knee loading (increased abduction/valgus angles and moments), and higher ground reaction forces [ 44 , 45 ]. These findings establish lower extremity and trunk kinematics and kinetics as critical modifiable factors in ACL injury, emphasizing the necessity of biomechanically-informed interventions. Accordingly, this study will employ kinematic (joint angles) and kinetic (joint moments, ground reaction forces) parameters as primary outcome measures to assess intervention efficacy. The kinematic factors comprise trunk flexion, trunk lateral flexion, knee flexion, knee abduction, hip flexion, hip adduction and hip internal rotation, and ankle dorsiflexion. The kinetic factors include vertical ground reaction force (GRF), knee flexion, knee abduction, hip abduction, and hip external rotation moments. Secondary outcome measures Functional performance, assessed as a secondary outcome measure across the sagittal, frontal, and transverse planes, will be examined due to its strong clinical relevance to high-risk mechanisms of ACL injury and its contribution to improving ecological validity [ 46 ]. The tuck jump test, single-leg triple crossover-hop for distance test, 90º medial rotation hop for distance test, and single-leg medial side triple hop for distance test will be administered to evaluate functional performance tests. Participant timeline {13} The study will consist of two measurement phases: a pre-test conducted before the intervention and a post-test administered after eight weeks for all participants. (Fig. 1 ) Sample size {14} To determine the minimum required sample size, descriptive statistics from previous studies by Sheikhi et al. [ 34 ] and Gholami et al. [ 28 ] will be utilized in conjunction with the G*Power software (version 3.1.9.2; University of Düsseldorf, Düsseldorf, Germany). A repeated measures analysis of variance (ANOVA) will be employed to assess the interaction effect between group and time, based on a statistical power of 80%, an alpha level of 0.05, a beta of 0.20, and a medium effect size of 0.25. Accordingly, a minimum of 14 participants per group is required. To account for a potential 10% drop-out rate and to enhance statistical power, the final sample size will be increased to 16 participants per group, resulting in a total of 48 participants. This effect size is consistent with improvements observed in hip and knee biomechanics following interventions in previous studies [ 28 , 34 ]. Recruitment {15} Participants will be recruited through targeted advertising, direct contact with coaches and university sports teams, and the dissemination of information via virtual platforms. All athletes from Tehran universities in volleyball, futsal, handball, and basketball are invited to participate in this study. Eligible participants will be selected based on predetermined inclusion and exclusion criteria. Assignment of interventions: allocation Sequence generation {16a} Randomization will be conducted using a freely accessible web-based tool ( http://randomizer.org/ , Social Psychology Network, Middletown, CT, USA; accessed on 22 June 2013). An independent researcher will generate the allocation sequence without involvement in the recruitment process. Randomization will be conducted using pre-prepared numbers ranging from 1 to 48, each enclosed in a sealed, opaque envelope and placed in a box to ensure allocation concealment. Participants will be randomly allocated in a 1:1:1 ratio to one of three groups: (1) NLP (n = 16), (2) DL (n = 16), and (3) control (n = 16) [ 34 ]. Upon completion of the study, participants will be informed of the group to which they have been assigned for intervention. Concealment mechanism {16b} The random numerical sequence was placed in sealed, opaque envelopes and stored in a box to ensure allocation concealment. An independent researcher, blinded to the baseline assessment, opened the envelopes based on group assignment and subsequently conducted the training sessions. Implementation {16c} Group allocation, participant enrollment, and assignment to intervention groups will be conducted by an independent researcher who is not involved in other aspects of the study. Two sports science professionals, each with a minimum of five years of experience in ACL injury prevention programs, will be present throughout the intervention. They will provide instruction, oversee the correct execution of exercises, and ensure adherence to intervention procedures. They are also familiar with the exercise protocols. Assignment of interventions: Blinding Who will be blinded? {17a} The present study will employ a single-blind design, in which only the outcome assessors are blind to their group allocation. Outcome measures are assessed at baseline and post-test by a blinded assessor who remains unaware of both the study hypothesis and methodology. Procedure for unblinding if needed {17b} Our process avoids the identification of information for our participants or group of outcomes from our controlled trial to the participants and/or investigators conducting the study. Data collection and management Plans for assessment and collection of outcomes {18a} Kinetic and kinematic data during the single-leg drop vertical jump test will be simultaneously collected using a force plate (Bertec corporation, Columbus, OH), sampling at 1200 Hz, and a motion analysis system (Kestrel 8.0 motion analysis, US), sampling at 240 Hz. Reflective markers will be placed on the iliac crest, ASIS, posterior superior iliac apine (PSIS), greater trochanters, medial and lateral femoral epicondyles, medial and lateral malleolus, 1st and 5th metatarsal heads, and the heel of their shoes. In addition, clusters of four markers attached to rigid shells will be placed on their thighs and legs [ 47 ]. The plug-in gait marker set will be employed for motion capture [ 27 ]. Marker trajectories will be recorded using cortex software (Motion Analysis Corporation, Santa Rosa, CA) and an eight-camera motion analysis system (Eagle cameras; Motion Analysis Corporation). A static calibration trial will be conducted with the athletes standing in the anatomical position. The marker data will be cut off at a frequency of 15 Hz, while the force data will be cut off at a frequency of 50 Hz. Depending on the type of task and the markers attached to the trunk, pelvis, knees, and ankles, the cameras cover a volume of space in the X, Y, and Z axes of 3×4×2.5, respectively [ 48 ]. This results in joint angles of flexion/extension, abduction/adduction, and internal/external rotation. The midpoint between the medial and lateral epicondyles of the femur and the medial and lateral malleolus will be used to estimate the centers of the knee and ankle joints, respectively. The hip joint center will be estimated using a regression method [ 49 ]. Joint angles represent the orientation of the distal segment's local coordinate system relative to the proximal segment's [ 50 ]. Initial contact and toe-off were identified as the instances when the vertical GRF first exceeded 10 N and subsequently fell below 10 N, respectively, before take-off [ 27 ]. The period from initial contact (vGRF > 10 N) to 100 ms post-initial contact was defined as the landing phase [ 51 ]. All joint moments will be reported as external moments and calculated using the inverse dynamics method. Joint moments and vertical GRF will be normalized to body weight. For each participant, the data will be averaged across five successful trials of the single-leg drop vertical jump test. Visual3D software (C-Motion Inc., Rockville, MD, USA) will be used to construct the biomechanical model and analyze the collected data. Data processing will be performed using MATLAB engineering software (version 8.4, 2014b). Biomechanics during single-leg drop-vertical jump test with neurocognitive load Participants will be instructed to stand barefoot on a 30 cm-high box, with their arms in a self-selected position. They will then be directed to perform a single-leg landing onto a force plate positioned 30 cm from the box, immediately followed by a maximal vertical jump and a subsequent landing in the initial position. Each participant will complete five trials, and the mean value of these trials will be used for statistical analysis. Trials will be deemed invalid and repeated if the participant loses balance, falls, makes contact with the ground using the contralateral foot, or performs a jump onto the box instead of a landing. To minimize the effects of fatigue, a one-minute rest interval will be provided between each trial [ 52 ]. The dominant leg is defined as the leg that the participant prefers to use to land after a jump [ 27 ]. The single-leg drop vertical jump test has demonstrated good reliability. It has reported intraclass correlation coefficients (ICC ≤ 0.75) [ 53 ]. Neurocognitive load The Stroop effect is a cognitive task commonly employed to impose cognitive load during jumping and landing assessments. An examiner stands approximately three meters in front of the participant, at eye level, and presents a series of color words (e.g., blue, red, black, yellow). Each word is displayed in a font color that either matches or conflicts with the semantic meaning of the word, thereby eliciting the Stroop effect. Participants will be instructed to respond to the font color of the word, rather than its semantic content, upon landing. Trials in which participants provide an incorrect response to the color will be considered invalid and repeated. The Stroop effect represents a form of cognitive interference that affects reaction time and has been shown to increase response latency compared to tasks without such interference [ 54 ]. The Stroop task will serve as the cognitive load imposed on participants during the execution of functional performance and single-leg drop vertical jump tests. The inclusion of this cognitive component is intended to enhance the ecological validity and generalizability of the assessments by simulating the cognitive demands commonly encountered in real-world athletic environments. Tuck jump test The tuck jump test will be used to identify athletes at high risk for ACL injury and to assess functional performance. This test is a practical and effective motor assessment tool designed to identify neuromuscular deficits related to ACL injury, particularly in landing technique during repetitive plyometric activity. Excellent reliability was demonstrated, with ICC values ranging from 0.94 to 0.96, [ 39 ]. This test requires participants to perform continuous maximal height jumps for 10 seconds within a predefined spatial range. The scoring system comprises ten quantitative dual-item measures, which collectively evaluate neuromuscular impairments across four domains: ligament dominance, quadriceps dominance, trunk dominance, and leg dominance. Additionally, the test facilitates the assessment of fatigue effects and deficits in feedforward and predictive neuromuscular responses [ 36 ]. Participants will be instructed to position their feet at the center of a marked rectangle on the floor, which is composed of four smaller rectangles, each measuring 41 cm in length and 35 cm in width. Before the test, standardized instructions will be provided, detailing the procedure, including the requirement to raise the knees to hip height and to attempt landing within the center of the marked rectangle with the feet positioned shoulder-width apart. To identify anatomical landmarks in two-dimensional kinematic analysis, reflective markers will be placed on the following anatomical locations: the acromioclavicular joint, sternum, anterior superior iliac spine (ASIS), greater trochanter of the femur, medial and lateral epicondyles of the femur, medial and lateral malleoli of the ankle, as well as the first and fifth metatarsal heads. During each trial, performance will be recorded using two video cameras (Galaxy A12, SM-A127F/DS) positioned in the frontal and sagittal planes, each placed at a distance of 3 meters from the participant and aligned with waist height. To ensure accurate identification of movement errors, participants will wear minimal clothing necessary for appropriate video analysis. Following the test, all recorded trials will be analyzed using Kinovea software (Kinovea, version 0.8.15, USA), through which any biomechanical deficits exhibited during jumping and landing will be systematically evaluated and scored. According to Dingenen et al., 2D kinematic analysis (ICC = 0.90–0.99) and kinovea software have demonstrated high reliability [ 55 ]. The scoring system is designed such that participants are assigned a score of “one” or “two” if they fail to meet the specified performance criteria, with the score reflecting the severity of the observed defect. A score of “zero” is assigned when the performance criteria are satisfactorily met. A movement pattern is deemed ineffective if an associated technical deficiency is observed at least twice within the ten-second testing period [ 56 ]. Single-leg triple crossover-hop for distance test To perform the test, the athlete begins by standing on the dominant leg behind a designated starting line. The task involves executing three consecutive maximal forward jumps, while alternately zigzagging to the left and right across a 15 cm-wide strip on the ground, without making contact with the strip. On the third and final jump, the athlete is required to stabilize and maintain the landing position for two seconds. The jump distance will be measured from the starting line to the heel of the landing foot and recorded as the participant's performance. If the participant loses balance, makes ground contact with the non-dominant foot, or performs an additional jump, the trial will be deemed invalid and subsequently repeated. The single-leg triple crossover hop for distance test has demonstrated excellent validity, with ICC values ranging from 0.89 to 0.99, [ 57 ]. The 90 medial-rotation hop for distance test Participants will be instructed to stand on the dominant leg with the medial aspect of the foot perpendicular to the intended jump direction. They should execute the jump with approximately 90 degrees of internal rotation in the transverse plane during the forward phase. Before takeoff, the foot should not be aligned with the intended direction of the jump. However, upon landing, the foot should be oriented in the direction of the jump. The examiner will visually assess and verify this alignment. If the participant fails to land in alignment with the direction of the jump, defined as a deviation greater than 10 degrees, the trial will be considered invalid and will be repeated. The jump distance will be measured from the medial aspect of the foot at take-off to the tip of the toes at landing. The 90° medial rotation hop for the distance test has demonstrated excellent test-retest reliability (ICC = 0.93–0.98) [ 46 ]. Single-leg medial side triple hop for distance test Participants will be instructed to stand on their dominant leg with the medial side of their foot perpendicular to the intended direction of their hop. They will then perform three consecutive medial hops, landing on the same foot each time. Upon the final landing, the foot must remain perpendicular to the intended direction of the hop. The total hop distance will be measured from the medial aspect of the foot at initial takeoff to the medial aspect of the foot at final landing. The trial will be deemed invalid and repeated if the participant is unable to maintain balance for at least two seconds after landing, touches the ground with their upper limbs or contralateral leg, or takes additional small jumps after landing. A 30-second rest period will be provided between each attempt. The single-leg medial side triple hop for the distance test has shown excellent reliability when tested repeatedly (ICC = 0.93–0.98) [ 46 ]. Plans to promote participant retention and complete follow‑up {18b} The researcher will monitor each participant's adherence to the prescribed exercise protocol through regular phone calls, email correspondence, and in-person meetings. To further motivate participants, a small gift will be provided upon completion of the study. In addition, we count on the commitment of the athletic trainers to ensure that it can be carried out in the most correct way possible. Data management {19} All collected data will be coded using numerical identifiers to ensure participant anonymity. Additionally, the data will be disseminated through two primary channels: publication in academic papers and submission to a trial registration website. Confidentiality {27} The data sheets and electronic files that have been collected will not contain any personal information, and each participant will be given a unique study code. Plans for collection, laboratory evaluation, and storage of biological specimens for genetic or molecular analysis in this trial/future use {33} This study did not include the collection of biological specimens from participants. Statistical methods Statistical methods for primary and secondary outcomes {20a} Data distribution normality and variance homogeneity will be assessed using the Shapiro-Wilk and Levene's tests, respectively. Parametric tests were applied when normality assumptions were met; otherwise, nonparametric alternatives were used. A 3×2 repeated measures ANOVA test will be performed to determine the differences between the three groups (control, DL, and NLP) and time (pre-test and post-test). Then, post hoc comparisons with a Bonferroni correction will be performed. If the assumption of sphericity is violated (as evidenced by unequal variances between paired measurement groups), the Greenhouse-Geisser correction will be applied. The pretest-to-posttest within-group factor will be considered the main effect of time, and the between-group factor will be considered the main effect of group. The percentage change from pretest to posttest will be calculated. Partial eta squared (ηp²) will compute effect sizes (ES) to enhance statistical power. The effect size will be classified as small (0.01), medium (0.06), or large (0.14) [ 39 ]. Statistical analyses will be performed at a 95% confidence level (p < 0.05) using IBM SPSS statistics software, version 26 (IBM Corp., Armonk, NY, USA). Interim analyses {21b} The principal investigator will have access to the interim results and will make the final decision about whether to terminate the trial. Methods for additional analyses (e.g., subgroup analyses) {20b} For subgroup analyses, participants’ demographic characteristics (e.g., number of athletes, age, body mass, height, body mass index, sports experience, and sport type) will be compared using a one-way analysis of variance (ANOVA). If the omnibus test yields a significant result, post hoc independent t-tests will be conducted. Methods in analysis to handle protocol non‑adherence and any statistical methods to handle missing data {20c} Participant adherence to the intervention will be monitored by recording attendance at each session. Participants who miss more than three consecutive sessions, whether due to injury or other reasons, will be classified as having not completed the intervention. To mitigate the risk of noncompliance with the study protocol, the sample size will be increased by 10%. However, if nonadherence persists, the intention-to-treat (ITT) analysis will be applied. In cases of missing data, the multiple imputation method will be used to address the gaps appropriately. Plans to give access to the full protocol, participant‑level data, and statistical code {31c} The study protocol will be published in the journal, and the corresponding author may be contacted if you would like access to the underlying data. Oversight and monitoring Composition of the coordinating center and trial steering Committee {5d} The study does not comprise a steering committee, management team, or oversight body beyond the lead author and the protocol contributor. Composition of the data monitoring committee, its role, and reporting structure {21a} The data monitoring committee will consist of researchers who have no competing interests in this study. Committee members will periodically evaluate participants and make relevant recommendations. Adverse event reporting and harms {22} A dedicated group will use a communication platform to facilitate the collection, assessment, reporting, and management of both solicited and self-reported adverse events and other undesirable effects related to the interventions or trial conduct. Participants will be encouraged to report their conditions through the platform. Frequency and plans for auditing trial conduct {23} A detailed timetable for implementation will be included in the protocol, and a checklist will be used to track the completion of each item. Plans for communicating important protocol amendments to relevant parties (e.g., trial participants, ethical committees) {25} Should any substantial amendments to the protocol be made, the relevant parties will be apprised of them via notifications on the WhatsApp messaging platform. Additionally, any potential amendments to the protocol will be communicated to the Ministry of Health via the IRCT website. Dissemination plans {31a} The research findings will be disseminated to study participants, healthcare practitioners, and the broader public via peer-reviewed scientific journals and publicly accessible results databases. Discussion Future expectations of the study This study designed a randomized controlled trial protocol to compare the effects of plyometric training based on DL and NLP approaches on biomechanical and functional outcomes in athletes at high risk for an ACL injury. The main research question investigates whether variability-based training (integrating NLP and DL with plyometrics) improves functional performance and landing biomechanics in high-risk ACL athletes compared to a control group. This field-based controlled trial is expected to advance ACL injury risk reduction programs by decreasing injury likelihood and refining return-to-sport criteria. By integrating sport-specific physical and cognitive indicators, this study aims to improve ecological validity and generalizability, better reflecting the multifaceted demands of athletic performance. The findings may inform enhanced rehabilitation protocols, injury risk reduction, and optimize ACL injury prevention strategies. To facilitate knowledge translation, findings will be disseminated through workshops for athletic trainers and sports medicine practitioners, alongside presentations at scientific conferences and forums. Although neuromuscular and biomechanical differences exist between sexes, females exhibit greater knee valgus, reduced flexion at initial contact, and stiffer landings that are consistently associated with higher ACL injury risk [ 58 ]. The current intervention protocol is hypothesized to reduce ACL injury incidence in high-risk female athlete populations through the modification of landing biomechanics toward safer movement patterns. Limitations This study has several limitations. First, the sample was restricted to male athletes, limiting the generalizability of the findings to female athletes. Second, the study did not include an electromyographic analysis of lower-limb muscle activity, which could have provided valuable insights into the neuromuscular mechanisms underlying landing biomechanics. Third, the absence of a comparison group that only received plyometric training limits the ability to determine whether the observed effects in the intervention groups were due to the variability-based approaches (NLP and DL) or the plyometric training itself. Fourth, the predominance of athletes recruited from a single center may introduce bias and limit the generalizability of the findings. Fifth, laboratory-based biomechanical assessments, even those incorporating cognitive tasks like the Stroop test, still differ from in-game dynamics. Strengths The study has high ecological validity via neurocognitive load. Given that the present study integrates two ACL injury prevention training protocols previously shown to have large effect sizes, the resulting intervention may serve as an effective and ecologically valid training program for enhancing injury prevention strategies and reducing injury risk among athletes participating in indoor ball sports. If the results are favorable, the proposed training protocol could provide physiotherapists, coaches, and sports science professionals with a practical framework for guiding injury prevention strategies and facilitating a safe and effective return to sports. Trial status This trial was prospectively registered in the IRCT on 15 March 2025 (Registration Code: IRCT20210602051477N3). The recruitment of participants will take place from September to October 2025. Abbreviations ACL Anterior cruciate ligament NLP Non-linear pedagogy DL Differential learning. Declarations Acknowledgements Not applicable. Authors’ contributions {31b} MHG serves as the chief investigator and guarantor of the study; he conceived the research idea and led the development of the study proposal and protocol. MHN, HS, MKT, and AB contributed to the study design and the formulation of the proposal. All authors reviewed and approved the final manuscript. Funding {4} The authors declare that they did not receive any funding from public, commercial, or nonprofit agencies to conduct this research. Availability of data and materials {29} Upon publication in this journal, the final test dataset will be made publicly available to all readers. Ethics approval and consent to participate {24} This study received ethical approval from the biomedical research ethics committee of Kharazmi University (Approval Code: IR.KHU.REC.1403.169). Additionally, the trial was prospectively registered on the IRCT (Registration Code: IRCT20210602051477N3). Written informed consent will be obtained from all eligible participants before their inclusion in the study. Consent for publication {32} All of the authors have consented to the publication of this work. Competing interests {28} The authors declare that they have no financial or personal relationships with any individuals or organizations that could have inappropriately influenced the conduct or reporting of this study. References Nessler T, Denney L, Sampley J. ACL injury prevention: what does research tell us? Curr Rev Musculoskelet Med. 2017;10:281–8. Bolt R, Heuvelmans P, Benjaminse A, Robinson MA, Gokeler A. An ecological dynamics approach to ACL injury risk research: a current opinion. Sports Biomech. 2024;23(10):1592–605. Kaeding CC, Léger-St-Jean B, Magnussen RA. Epidemiology and diagnosis of anterior cruciate ligament injuries. Clin Sports Med. 2017;36(1):1–8. Gokeler A, Seil R, Kerkhoffs G, Verhagen E. A novel approach to enhance ACL injury prevention programs. 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Sex-Specific Brain Activations during Single-Leg Exercise. Int J Sports Phys Therapy. 2022;17(7):1249. Supplementary Files Additionalfile1NLPandDLprotocol.docx Additionalfile2fidelitychecklist.docx SPIRITchecklistTrial.docx TIDieRChecklistWord.docx Cite Share Download PDF Status: Published Journal Publication published 17 Feb, 2026 Read the published version in Trials → Version 1 posted Editorial decision: Accept 08 Feb, 2026 Reviewers agreed at journal 08 Jan, 2026 Reviewers invited by journal 15 Aug, 2025 Editor assigned by journal 11 Aug, 2025 First submitted to journal 25 Jul, 2025 You are reading this latest preprint version Research Square lets you share your work early, gain feedback from the community, and start making changes to your manuscript prior to peer review in a journal. As a division of Research Square Company, we’re committed to making research communication faster, fairer, and more useful. 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diagram.\u003c/p\u003e","description":"","filename":"1.png","url":"https://assets-eu.researchsquare.com/files/rs-7114294/v1/21e89d016c24c1cbd9d08089.png"},{"id":103251217,"identity":"690711fa-aa99-48ad-821c-72d8946c161f","added_by":"auto","created_at":"2026-02-23 16:06:26","extension":"pdf","order_by":0,"title":"","display":"","copyAsset":false,"role":"manuscript-pdf","size":1925429,"visible":true,"origin":"","legend":"","description":"","filename":"manuscript.pdf","url":"https://assets-eu.researchsquare.com/files/rs-7114294/v1/10505454-a7f0-4d7e-b7b6-c8515e65a024.pdf"},{"id":89658406,"identity":"0c1dd9ba-9a8e-444e-9850-18e1420eda69","added_by":"auto","created_at":"2025-08-22 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10:33:26","extension":"docx","order_by":6,"title":"","display":"","copyAsset":false,"role":"supplement","size":39944,"visible":true,"origin":"","legend":"","description":"","filename":"SPIRITchecklistTrial.docx","url":"https://assets-eu.researchsquare.com/files/rs-7114294/v1/8de262f71c388f5836ff6dd4.docx"},{"id":89659794,"identity":"7ef7c482-2a59-4e33-868a-23ad95a6d49b","added_by":"auto","created_at":"2025-08-22 10:57:26","extension":"docx","order_by":7,"title":"","display":"","copyAsset":false,"role":"supplement","size":32473,"visible":true,"origin":"","legend":"","description":"","filename":"TIDieRChecklistWord.docx","url":"https://assets-eu.researchsquare.com/files/rs-7114294/v1/2ef5bed238ccb9493f4c41f8.docx"}],"financialInterests":"","formattedTitle":"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","fulltext":[{"header":"Administrative information","content":"\u003cp\u003eNote: the numbers in curly brackets in this protocol refer to SPIRIT checklist item numbers. The order of the items has been modified to group similar items (see http://www.equator-network.org/reporting-guidelines/spirit-2013-statement-defining-standard-protocol-itemsfor- clinical-trials/).\u003c/p\u003e\n\u003ctable border=\"1\" cellspacing=\"0\" cellpadding=\"0\"\u003e\n \u003ctbody\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eTitle {1}\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eComparison 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\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eTrial registration {2a and 2b}.\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eIRCT20210602051477N3\u003c/p\u003e\n \u003cp\u003e(https://www.irct.ir/trial/69146)\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eProtocol version {3}\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eVersion 5 of 2025-03-15\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eFunding {4}\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eThe authors declare that they did not receive any funding from public, commercial, or nonprofit agencies to conduct this research.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eAuthor details {5a}\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eMajid Hamoongard (Corresponding author), Faculty of Physical Education and Sports Sciences, Kharazmi University, Tehran, Iran.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eMalihe Hadadnezhad, Faculty of Physical Education and Sports Sciences, Kharazmi University, Tehran, Iran.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eHassan Sadeghi, Faculty of Physical Education and Sports Sciences, Kharazmi University, Tehran, Iran.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eMehdi Khaleghi Tazji, Faculty of Physical Education and Sports Sciences, Kharazmi University, Tehran, Iran.\u003c/p\u003e\n \u003cp\u003eAnne Benjaminse, Department of Human Movement Sciences, University Medical Center Groningen, University of Groningen, Netherlands.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eName and contact information for the trial sponsor {5b}\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eKharazmi University, Tehran, Iran.\u0026nbsp;\u003c/p\u003e\n \u003cp\u003eAddress: Kharazmi University No.43 South Mofateh St Tehran, 15719-14911 Iran. Telephone: +98 (21) 88329220. Email: [email protected].\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003ctr\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eRole of sponsor {5c}\u003c/p\u003e\n \u003c/td\u003e\n \u003ctd valign=\"top\"\u003e\n \u003cp\u003eNo roles in the collection, management, analysis, and interpretation of the data; writing of the report; or the decision to submit the report for publication.\u003c/p\u003e\n \u003c/td\u003e\n \u003c/tr\u003e\n \u003c/tbody\u003e\n\u003c/table\u003e"},{"header":"Introduction","content":"\u003ch3\u003eBackground and rationale {6a}\u003c/h3\u003e\n\u003cp\u003eAnterior cruciate ligament (ACL) injuries are complex, challenging, and multi-factorial, and they are most commonly seen in football, volleyball, handball, and basketball [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. ACL tears are among the most prevalent traumatic knee injuries in sports [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Despite advances in research and the adoption of injury prevention programs, the rate of these injuries has increased twofold over the past two decades [\u003cspan citationid=\"CR3\" class=\"CitationRef\"\u003e3\u003c/span\u003e]. ACL ruptures occur during dynamic activities that require high knee loading, such as single-leg landing after a jump [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e]. Competitive and recreational athletes are at the highest risk of injury [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Among young athletes, the risk of sustaining a secondary ACL injury within two to five years after the initial injury has been reported to range from 25–35% [\u003cspan citationid=\"CR5\" class=\"CitationRef\"\u003e5\u003c/span\u003e]. ACL tear can be a debilitating and life-changing injury that can result in a long rehabilitation period for athletes, difficulty returning to pre-injury performance levels, and significant healing complications [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e, \u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. This injury can increase the risk of cartilage damage and osteoarthritis [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. Given these long-term consequences, prevention and risk reduction programs for ACL injuries should be a high priority [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eInjury prevention programs typically integrate a combination of plyometric, resistance, balance, and technique training, all of which are designed to promote neuromuscular adaptations [\u003cspan citationid=\"CR6\" class=\"CitationRef\"\u003e6\u003c/span\u003e]. Specifically, plyometric training has been shown to mitigate ACL injury risk by facilitating the retraining of proper movement techniques and body mechanics [\u003cspan citationid=\"CR1\" class=\"CitationRef\"\u003e1\u003c/span\u003e]. Plyometric training is widely used to improve athletes' rate of force development and explosive power, as it enhances neuromuscular function and motor control [\u003cspan citationid=\"CR8\" class=\"CitationRef\"\u003e8\u003c/span\u003e]. A meta-analytic review reported that injury prevention programs incorporating plyometric training were associated with a 60% reduction in injury risk per 1,000 hours of training and competition [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTeam sport performance is shaped by both physical and cognitive abilities, such as decision-making, anticipation, and rapid information processing, essential for adapting to dynamic game demands [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Variability in playing conditions emerges from a range of constraints associated with the athlete, the task, and the environment [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. In sports, athletes routinely perform complex movements under diverse constraints, including varied body positions, the presence of opponents, and limited time for decision-making and execution [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e]. Nevertheless, the majority of functional performance tests employed to assess and prepare injured athletes for return to sport do not adequately reflect the complexity and ecological validity of competitive environments [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. This emphasizes the need for more ecologically valid and sport-specific tests that more accurately reflect the multifaceted demands of athletic performance [\u003cspan citationid=\"CR12\" class=\"CitationRef\"\u003e12\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eTask constraints may include the athlete's goal and any rules or factors that determine or limit the dynamics of the athlete's response (such as a defender blocking the athlete's path) [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e]. Environmental constraints may include characteristics such as terrain type and weather conditions [\u003cspan citationid=\"CR2\" class=\"CitationRef\"\u003e2\u003c/span\u003e]. Athlete-related constraints include intrinsic factors such as physical and psychological attributes, including anthropometric measurements, attentional capacity, motivational states, and anxiety levels [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. These constraints act as boundary conditions that modulate and guide an athlete's self-organized movement patterns in dynamic performance environments [\u003cspan citationid=\"CR11\" class=\"CitationRef\"\u003e11\u003c/span\u003e]. The influence of various constraints is mediated by the athlete’s capacity to perceive and interpret them [\u003cspan citationid=\"CR14\" class=\"CitationRef\"\u003e14\u003c/span\u003e]. Since sports environments are unpredictable, rehabilitation must be adaptable, enabling athletes to adjust to shifting demands based on their perceptual-cognitive abilities [\u003cspan citationid=\"CR10\" class=\"CitationRef\"\u003e10\u003c/span\u003e].\u003c/p\u003e\u003cp\u003ePrevious research has shown that training programs integrating neurocognitive strategies are more effective at reducing the risk of ACL injury than programs focusing exclusively on neuromuscular control [\u003cspan citationid=\"CR4\" class=\"CitationRef\"\u003e4\u003c/span\u003e, \u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e, \u003cspan citationid=\"CR15\" class=\"CitationRef\"\u003e15\u003c/span\u003e]. Reviews indicate that variability-based training outperforms other cognitive methods in enhancing biomechanical factors linked to ACL injury risk [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. The traditional motor-learning paradigm prioritizes repetitive practice aimed at maintaining an \"ideal\" movement pattern [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. In contrast, the ecological dynamics framework posits that no movement is ever reproduced identically in authentic sporting contexts; each action is uniquely shaped by the interaction of individual, task, and environmental constraints at each moment [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e]. While movement variability was traditionally viewed as error or noise, current evidence indicates that regulated variability enhances performance adaptability, self-organization process, and mitigates injury risk [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. Within the ecological dynamic framework, motor learning emerges from the continuous interaction of the individual, task, and environmental constraints [\u003cspan citationid=\"CR19\" class=\"CitationRef\"\u003e19\u003c/span\u003e]. These constraints are conceptualized as boundaries that shape and guide the emergence of behavior [\u003cspan citationid=\"CR20\" class=\"CitationRef\"\u003e20\u003c/span\u003e]. This dynamic interplay compels learners to explore and stabilize functional, effective movement patterns during goal-directed activities [\u003cspan citationid=\"CR17\" class=\"CitationRef\"\u003e17\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eA key challenge in applying variability to training is fostering exploratory behavior [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e]. Exposing athletes to exploratory performance conditions or increasing variability in training protocols may allow them to develop new motor skills and capabilities [\u003cspan citationid=\"CR21\" class=\"CitationRef\"\u003e21\u003c/span\u003e]. Practice variability enhances motor learning by promoting skill generalization, fostering self-organization, enabling optimal movement discovery, encouraging exploration, and improving cognitive flexibility [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Reduced movement variability may hinder learners' ability to adapt flexibly to task-specific constraints and dynamically changing environments [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]. The theory of optimal movement variability posits that therapeutic interventions should avoid enforcing a single 'ideal' movement pattern [\u003cspan citationid=\"CR24\" class=\"CitationRef\"\u003e24\u003c/span\u003e]. Instead, programs should target functional limitations by maintaining variability within an optimal range, thereby enhancing adaptability and performance [\u003cspan citationid=\"CR13\" class=\"CitationRef\"\u003e13\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNonlinear pedagogy (NLP) and differential learning (DL) approaches are based on the idea that movement variability comes from the way multiple constraints interact [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. In particular, DL promotes exposure to a wide range of movement patterns, facilitating the exploration of diverse motor solutions and enhancing adaptability [\u003cspan citationid=\"CR25\" class=\"CitationRef\"\u003e25\u003c/span\u003e]. The DL exercises promote engagement with diverse movement patterns rather than avoidance of variability, fostering motor learning and adaptability through exploratory behavior [\u003cspan citationid=\"CR26\" class=\"CitationRef\"\u003e26\u003c/span\u003e]. The NLP approach emphasizes acquiring motor skills through exploratory behavior and developing individualized movement solutions [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. The principal aim of NLP is to improve adaptability through structured variability during practice, achieved by systematically manipulating task and environmental constraints to evoke context-dependent motor responses [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe DL approach has consistently demonstrated efficacy in optimizing ACL-protective biomechanics and functional performance, outperforming conventional motor learning paradigms in comparative studies [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e, \u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e]. Preliminary evidence suggests the NLP approach may improve specific biomechanical factors more effectively than DL, though current findings remain inconclusive and require further validation [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. A comprehensive literature review revealed no existing studies directly comparing DL and NLP approaches for improving biomechanical and functional factors in high-risk ACL athletes.\u003c/p\u003e\u003cp\u003e\u003cb\u003eJustification for the study\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eObjectives {7}\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003ePrimary aim\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe primary aim of this study is to compare the effects of plyometric training using DL versus NLP on biomechanical factors in athletes at high risk of ACL injury.\u003c/p\u003e\u003cp\u003e\u003cb\u003eSecondary aim\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe secondary aim of this study is to compare the effects of plyometric training using DL versus NLP on functional performance in athletes at high risk of ACL injury.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePICO question\u003c/b\u003e\u003c/p\u003e\u003cp\u003eCan variability-based training approaches, specifically NLP and DL integrated with plyometric training, enhance functional performance and landing biomechanics in athletes at high risk of ACL injury, relative to a control group?\u003c/p\u003e\u003cp\u003e\u003cb\u003eStudy hypothesis\u003c/b\u003e\u003c/p\u003e\u003cp\u003eWe hypothesize that both DL and NLP will outperform the control, with potential differences between them.\u003c/p\u003e\u003cp\u003e\u003cb\u003eTrial design {8}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThis study is a three-arm, single-assessor blind, randomized controlled trial employing a parallel-group design to be conducted among male athletes at high risk for ACL injury. Participants will be randomly allocated in a 1:1:1 ratio to one of three groups: NLP, DL, and control. The superiority framework will guide the statistical analysis, with the null hypothesis (H0) being that there is no significant difference between the intervention and control groups, and the alternative hypothesis (H1) being that the intervention group demonstrates superior outcomes. This study received ethical approval from the biomedical research ethics committee of Kharazmi University (Approval Code: IR.KHU.REC.1403.169). Furthermore, the trial was prospectively registered in the Iranian registry of clinical trials (IRCT) under the registration code: IRCT20210602051477N3. The protocol conforms to established international reporting guidelines, including SPIRIT, CONSORT, and TIDieR [\u003cspan additionalcitationids=\"CR30\" citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e–\u003cspan citationid=\"CR31\" class=\"CitationRef\"\u003e31\u003c/span\u003e]. The study flowchart is illustrated in Table\u0026nbsp;\u003cspan refid=\"Tab1\" class=\"InternalRef\"\u003e1\u003c/span\u003e and Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c4\" colnum=\"4\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c5\" colnum=\"5\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab1\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 1\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eRecommended protocol items scheduled for enrolment, interventions, and assessments according to evidence [\u003cspan citationid=\"CR29\" class=\"CitationRef\"\u003e29\u003c/span\u003e]\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"5\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u0026nbsp;\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eENROLMENT\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eALLOCATION\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c4\"\u003e\u003cp\u003eBASELINE\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c5\"\u003e\u003cp\u003eAFTER 8 WEEKS\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eTIMEPOINT\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003e-t\u003c/b\u003e\u003csub\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003e0\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003ePr\u003c/b\u003e\u003csub\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003ePo\u003c/b\u003e\u003csub\u003e\u003cb\u003e1\u003c/b\u003e\u003c/sub\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eENROLMENT\u003c/b\u003e:\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eEligibility screen\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eInformed consent\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e[Randomization]\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAllocation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eINTERVENTIONS\u003c/b\u003e:\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eNLP plus plyometric training\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDL plus plyometric training\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eControl\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e\u003cb\u003eASSESSMENTS\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u0026nbsp;\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTrunk flexion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTrunk lateral flexion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKnee flexion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKnee abduction\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip flexion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip adduction\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip internal rotation\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eAnkle dorsiflexion\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGround reaction force\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKnee flexion moment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eKnee abduction moment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip abduction moment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eHip external rotation moment\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTuck jump test\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSLTCH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e90MRH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eSLMTH\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u0026nbsp;\u003c/td\u003e\u003ctd align=\"left\" colname=\"c4\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c5\"\u003e\u003cp\u003e\u003cb\u003eX\u003c/b\u003e\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003ctfoot\u003e\u003ctr\u003e\u003ctd colspan=\"5\"\u003ePr\u003csub\u003e1\u003c/sub\u003e: Pre-test, Po\u003csub\u003e1\u003c/sub\u003e: Post-test, SLTCH: Single-leg triple crossover hop for distance test, 90MRH: The 90 medial rotation hop for distance test, SLMTH: Single-leg medial side triple hop for distance test.\u003c/td\u003e\u003c/tr\u003e\u003c/tfoot\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e"},{"header":"Methods","content":"\u003cp\u003e\u003cb\u003eParticipants, interventions, and outcomes\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eStudy setting {9}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eMcKinney et al. define competitive athletes as individuals training \u0026gt; 6 hours weekly with performance-focused objectives and regular participation in organized competitions (e.g., collegiate sports) [\u003cspan citationid=\"CR32\" class=\"CitationRef\"\u003e32\u003c/span\u003e]. Participants will include 16 male athletes per group (ages 18–26) from Tehran universities, actively competing in elite futsal, volleyball, handball, or basketball programs. The focus on male athletes was justified by their elevated ACL injury risk, understudied prevention programs, and practical recruitment advantages [\u003cspan citationid=\"CR33\" class=\"CitationRef\"\u003e33\u003c/span\u003e]. This study will include two intervention groups, one using DL and the other using NLP, as well as a control group. Data were collected at two time points: baseline (pre-intervention) and post-intervention (following eight weeks). Before the pre-test, participants will complete a standardized warm-up consisting of two sets of eight bilateral squat repetitions, two sets of five bilateral jump squat repetitions, and dynamic calf muscle stretching exercises [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eEligibility criteria {10}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe inclusion criteria will be: male collegiate athletes aged 18–26 years competing in futsal, basketball, volleyball, and handball [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e], body mass index (BMI) ranges from 18.5 to 25 kg/m\u003csup\u003e2\u003c/sup\u003e [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e], tuck jump test score ≥ 6 [\u003cspan citationid=\"CR35\" class=\"CitationRef\"\u003e35\u003c/span\u003e, \u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e], no observable spinal or lower limb malalignments per clinical examination [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], no history of musculoskeletal injury within the past year that would have resulted in extended absence from athletic participation [\u003cspan citationid=\"CR37\" class=\"CitationRef\"\u003e37\u003c/span\u003e], no history of ACL injury, and no medical history of neurocognitive, metabolic, auditory, or visual impairments[\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e, \u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e], and no history of concussion-related symptoms, such as recurrent headaches or migraines, oculomotor deficits, or balance disorders, within the past five years [\u003cspan citationid=\"CR38\" class=\"CitationRef\"\u003e38\u003c/span\u003e]. The exclusion criteria will be: recent injury prevention program participation (past year) and inadequate attendance (\u0026gt; 2 consecutive or \u0026gt; 3 total absences) [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003e Who will take informed consent? {26a}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe investigator (M.H.) will obtain written informed consent from all participants after providing a clear explanation of the potential benefits and risks of participation, as well as informing them of their right to withdraw from the study at any time. The researchers conducted this study following the principles outlined in the Declaration of Helsinki. Before enrollment, all participants will receive complete written and verbal disclosure of study procedures, potential benefits, and foreseeable risks. All data were anonymized and stored securely with access limited to the research team.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAdditional consent provisions for the collection and use of participant data and biological specimens {26b}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe informed consent document outlines the specific tests to be conducted and states that the data collected will not be reused beyond the scope of this study. As the study does not involve the collection or use of biological specimens from participants, no additional consent will be required.\u003c/p\u003e\u003cp\u003e\u003cb\u003eInterventions\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eExplanation for the choice of comparators {6b}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eEmerging motor learning paradigms that prioritize movement variability appear more effective than neurocognitive-focused interventions in enhancing biomechanical factors associated with ACL injury prevention [\u003cspan citationid=\"CR7\" class=\"CitationRef\"\u003e7\u003c/span\u003e]. While the superiority of NLP over DL has been attributed to factors such as cognitive flexibility, self-organization, and exploratory capabilities, this conclusion is primarily grounded in theoretical discussions rather than empirical evidence [\u003cspan citationid=\"CR18\" class=\"CitationRef\"\u003e18\u003c/span\u003e]. No empirical studies to date have evaluated the relative efficacy of DL and NLP paradigms in modifying biomechanical risk factors and functional performance among athletes at high risk of ACL injury.\u003c/p\u003e\u003cp\u003e\u003cb\u003eIntervention description {11a}\u003c/b\u003e\u003c/p\u003e\u003cp\u003ePlyometric training program\u003c/p\u003e\u003cp\u003ePlyometric-based injury prevention programs have demonstrated effectiveness in reducing injury risk and improving biomechanical factors associated with ACL injury [\u003cspan citationid=\"CR9\" class=\"CitationRef\"\u003e9\u003c/span\u003e]. The intervention will span eight weeks, comprising three sessions per week, each lasting 60 minutes, for a total of 24 training sessions. The protocol is structured into three progressive phases: technical, fundamental, and functional. The aim of the technical phase (weeks 1 and 2) is to enhance motor control and to develop correct jumping and landing techniques. This phase focuses on instructing participants in proper posture and joint alignment, and achieving soft landings. All exercises during this phase will be performed bilaterally. The fundamental phase (weeks 3 to 5) aims to enhance power, strength, and agility by progressively increasing the intensity and duration of the training sessions. During this phase, single-leg landings are introduced. The final stage, the performance phase (weeks 6 to 8), is designed to optimize athletic performance, with a focus on maximizing vertical and horizontal jump height and improving landing mechanics. A rest interval of one to two minutes will be provided between each exercise to allow for adequate recovery [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e] (Table\u0026nbsp;\u003cspan refid=\"Tab2\" class=\"InternalRef\"\u003e2\u003c/span\u003e).\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab2\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 2\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003ePlyometric training program [\u003cspan citationid=\"CR40\" class=\"CitationRef\"\u003e40\u003c/span\u003e]\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePhase I—Technique (1–2 wk)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePhase II—Fundamental (3–5 wk)\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePhase III—Performance (6–8 wk)\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003e1. Wall jumps: 20 s\u003c/p\u003e\u003cp\u003e2. Squat jumps: 15 s\u003c/p\u003e\u003cp\u003e3. Lunge jumps: 15 s\u003c/p\u003e\u003cp\u003e4. Horizontal jump: 8 reps\u003c/p\u003e\u003cp\u003e5. 180-degree jumps: 20 s\u003c/p\u003e\u003cp\u003e6. Forward–backward jumps over the line: 20 s\u003c/p\u003e\u003cp\u003e7. Jump over barriers: 8 reps\u003c/p\u003e\u003cp\u003e8. Lateral–medial jumps over the line: 20 s\u003c/p\u003e\u003cp\u003e9. Lateral jump over the line + vertical jump: 8 reps\u003c/p\u003e\u003cp\u003e10. Drop landing: 8 reps\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003e1. Vertical hop + athletic position in single-leg standing: 10 reps\u003c/p\u003e\u003cp\u003e2. Wall jumps: 30 s\u003c/p\u003e\u003cp\u003e3. Squat jumps: 2×15\u003c/p\u003e\u003cp\u003e4. Triple horizontal jump + vertical jump: 6 reps\u003c/p\u003e\u003cp\u003e5. 180-degree jumps: 15 s\u003c/p\u003e\u003cp\u003e6. Lunge jumps: 15 s\u003c/p\u003e\u003cp\u003e7. Jump over barrier + jump to platform: 6 reps\u003c/p\u003e\u003cp\u003e8. Lateral-medial jumps over barrier: 2×15\u003c/p\u003e\u003cp\u003e9. Forward-backward jumps over barrier: 2×15\u003c/p\u003e\u003cp\u003e10. Anterior drop jump + maximum vertical jump: 6 reps\u003c/p\u003e\u003cp\u003e11. Lateral drop jump + maximum vertical jump: 6 reps\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003e1. Vertical hop + athletic position in single-leg standing: 10 reps\u003c/p\u003e\u003cp\u003e2. Tuck jumps: 15 s\u003c/p\u003e\u003cp\u003e3. 180-degree horizontal jumps: 20 s\u003c/p\u003e\u003cp\u003e4. Lunge jumps with trunk rotation: 20 s\u003c/p\u003e\u003cp\u003e5. Maximum horizontal jump + maximum vertical jump: 6 reps\u003c/p\u003e\u003cp\u003e6. Forward–backward hops over the line: 15s\u003c/p\u003e\u003cp\u003e7. Lateral–medial hops over the line: 15 s\u003c/p\u003e\u003cp\u003e8. Horizontal hop: 4 reps\u003c/p\u003e\u003cp\u003e9. Lateral drop landing + maximum vertical jump + maximum horizontal jump: 6 reps\u003c/p\u003e\u003cp\u003e10. Horizontal hop over barriers + hop to\u003c/p\u003e\u003cp\u003ePlatform: 4 reps\u003c/p\u003e\u003cp\u003e11. Lateral and medial hop over barriers + hop to platform: 8 reps\u003c/p\u003e\u003cp\u003e12. Single-leg drop landing + maximum vertical hop: 4 reps\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eNonlinear pedagogy (NLP)\u003c/p\u003e\u003cp\u003eThis approach does not involve providing explicit instructions or feedback on executing an ideal movement pattern (in contrast to DL). Instead, it encourages participants to engage in self-directed exploration of movement solutions by manipulating task and environmental constraints. Through repeated practice under consistent constraints, individuals can discover a range of movement strategies, fostering the development of adaptive and individualized solutions [\u003cspan citationid=\"CR22\" class=\"CitationRef\"\u003e22\u003c/span\u003e]. Upon successful attainment of the desired outcome by participants, task constraints and environmental conditions are systematically modified to correspond with individual capabilities, thereby introducing novel challenges and fostering ongoing adaptation. Task and environmental constraints will be individually tailored based on each participant's specific tasks, skill level, and personal characteristics. However, instructors are not permitted to provide guidance or instruction on how the movement should be performed. In general, this approach is characterized by variability in practice conditions, with learners encouraged to explore individualized movement solutions within the given constraints. The task goal is clearly defined, repetition is permitted, but no external feedback or instructional cues are provided [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e, \u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e, \u003cspan citationid=\"CR41\" class=\"CitationRef\"\u003e41\u003c/span\u003e]. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and additional file 1.\u003c/p\u003e\u003cp\u003e\u003c/p\u003e\u003cdiv class=\"gridtable\"\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c1\" colnum=\"1\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c2\" colnum=\"2\"\u003e\u003c/div\u003e\u003cdiv align=\"left\" class=\"colspec\" colname=\"c3\" colnum=\"3\"\u003e\u003c/div\u003e\u003ctable float=\"Yes\" id=\"Tab3\" border=\"1\"\u003e\u003ccaption language=\"En\"\u003e\u003cdiv class=\"CaptionNumber\"\u003eTable 3\u003c/div\u003e\u003cdiv class=\"CaptionContent\"\u003e\u003cp\u003eKey characteristics of the differential learning and non-linear pedagogy strategies [\u003cspan citationid=\"CR23\" class=\"CitationRef\"\u003e23\u003c/span\u003e]\u003c/p\u003e\u003c/div\u003e\u003c/caption\u003e\u003ccolgroup cols=\"3\"\u003e\u003c/colgroup\u003e\u003cthead\u003e\u003ctr\u003e\u003cth align=\"left\" colname=\"c1\"\u003e\u003cp\u003eGroup\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNLP\u003c/p\u003e\u003c/th\u003e\u003cth align=\"left\" colname=\"c3\"\u003e\u003cp\u003eDL\u003c/p\u003e\u003c/th\u003e\u003c/tr\u003e\u003c/thead\u003e\u003ctbody\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eTarget\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eThe task goal was clear, and it was important to achieve it.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eThe task goal may be absent, but how the action was executed was important.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePattern\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eNo ideal pattern was prescribed; instead, participants generated individualized movement solutions based on their unique characteristics, task demands, and environmental constraints.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eNumerous prescribed patterns were provided, and participants adhered to them.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eDescription\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eWhile the task goal was clearly defined, specific movement patterns were not described.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eEach movement pattern and task goal were described.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003ePrescription\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003ePrescription was not allowed.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003ePrescription was encouraged.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eRepeat\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eRepetition was allowed.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eRepetition was not allowed.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eVariability\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eUnstructured movement variability was promoted through systematic manipulation of task and environmental constraints, directing participants' attention toward discovering adaptive movement solutions.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003evariability was encouraged by prescribing different movement patterns, and also manipulations of task and environmental constraints were allowed. Participants attended to the prescribed motor pattern.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eFeedback\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eFeedback was not allowed.\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eFeedback was not allowed.\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003ctr\u003e\u003ctd align=\"left\" colname=\"c1\"\u003e\u003cp\u003eInstructions\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c2\"\u003e\u003cp\u003eInstructions were allowed (to manipulate task constraints).\u003c/p\u003e\u003c/td\u003e\u003ctd align=\"left\" colname=\"c3\"\u003e\u003cp\u003eInstructions were encouraged (to prescribe always differing movement patterns).\u003c/p\u003e\u003c/td\u003e\u003c/tr\u003e\u003c/tbody\u003e\u003c/table\u003e\u003c/div\u003e\u003cp\u003e\u003c/p\u003e\u003cp\u003eDifferential learning (DL)\u003c/p\u003e\u003cp\u003eParticipants are not required to replicate identical movement patterns; each movement is executed in varied forms, and no feedback is provided during performance. The required movement patterns are introduced verbally before each exercise. Consequently, each exercise is performed in a novel manner without direct repetition, relying on the instructor's creativity to generate diverse movement variations[\u003cspan citationid=\"CR42\" class=\"CitationRef\"\u003e42\u003c/span\u003e]. The progression of each exercise is based on repetition without repetition, from simple to advanced interventions. In general, in this approach; the goal of the task may not exist but the way it is performed is important, there are varied movement patterns, movement patterns are prescribed in advance, repetition is not allowed, there is random variability and manipulation of the task and environment constraints is allowed, feedback is not allowed but varied movement instructions are prescribed [\u003cspan citationid=\"CR16\" class=\"CitationRef\"\u003e16\u003c/span\u003e]. Table\u0026nbsp;\u003cspan refid=\"Tab3\" class=\"InternalRef\"\u003e3\u003c/span\u003e and additional file 1.\u003c/p\u003e\u003cp\u003e\u003cb\u003eCriteria for discontinuing or modifying allocated interventions {11b}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe trial may be discontinued at the request of any participating subject if pain or injury occurs during the interventions.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStrategies to improve adherence to intervention protocols {11c}\u003c/b\u003e\u003c/p\u003e\u003cp\u003e To enhance adherence, weekly phone calls will be conducted to monitor each participant’s progress and gather feedback regarding any challenges encountered during the intervention. Additionally, motivational strategies will be employed, and participants will be informed of the potential benefits of the exercise program to further promote engagement and compliance. Exercise fidelity is a key measure of adherence and refers to athletes performing exercises with proper biomechanics, intensity, and completion of prescribed sets and repetitions [\u003cspan citationid=\"CR43\" class=\"CitationRef\"\u003e43\u003c/span\u003e]. Therefore, a fidelity checklist will be developed for trainers to monitor adherence, exercise execution, and compliance with prescribed frequency, intensity, time, and type (FITT) of exercises. Additional file 2\u003c/p\u003e\u003cp\u003e\u003cb\u003eRelevant concomitant care permitted or prohibited during the trial {11d}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eParticipants will be asked to maintain a regular diet and adequate rest, and to refrain from smoking, tobacco, medication, caffeine, and alcohol for 24 hours prior to testing.\u003c/p\u003e\u003cp\u003e\u003cb\u003eProvisions for post‑trial care {30}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe protocol poses no additional risks to participants beyond those inherent to general sporting activities, as it comprises controlled exercises and excludes the implementation of hazardous interventions. Trainers with recognized qualifications in injury prevention training will oversee the implementation of the training protocols and the management of potential confounding factors.\u003c/p\u003e\u003cp\u003e\u003cb\u003eOutcomes {12}\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003ePrimary outcome measures\u003c/b\u003e\u003c/p\u003e\u003cp\u003eConsistent evidence from multidimensional biomechanical analyses identifies three key ACL injury risk profiles. Including reduced sagittal-plane joint loading (decreased hip/knee flexion angles and moments), excessive frontal-plane knee loading (increased abduction/valgus angles and moments), and higher ground reaction forces [\u003cspan citationid=\"CR44\" class=\"CitationRef\"\u003e44\u003c/span\u003e, \u003cspan citationid=\"CR45\" class=\"CitationRef\"\u003e45\u003c/span\u003e]. These findings establish lower extremity and trunk kinematics and kinetics as critical modifiable factors in ACL injury, emphasizing the necessity of biomechanically-informed interventions. Accordingly, this study will employ kinematic (joint angles) and kinetic (joint moments, ground reaction forces) parameters as primary outcome measures to assess intervention efficacy. The kinematic factors comprise trunk flexion, trunk lateral flexion, knee flexion, knee abduction, hip flexion, hip adduction and hip internal rotation, and ankle dorsiflexion. The kinetic factors include vertical ground reaction force (GRF), knee flexion, knee abduction, hip abduction, and hip external rotation moments.\u003c/p\u003e\u003cp\u003e\u003cb\u003eSecondary outcome measures\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFunctional performance, assessed as a secondary outcome measure across the sagittal, frontal, and transverse planes, will be examined due to its strong clinical relevance to high-risk mechanisms of ACL injury and its contribution to improving ecological validity [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e]. The tuck jump test, single-leg triple crossover-hop for distance test, 90º medial rotation hop for distance test, and single-leg medial side triple hop for distance test will be administered to evaluate functional performance tests.\u003c/p\u003e\u003cp\u003e\u003cb\u003eParticipant timeline {13}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe study will consist of two measurement phases: a pre-test conducted before the intervention and a post-test administered after eight weeks for all participants. (Fig.\u0026nbsp;\u003cspan refid=\"Fig1\" class=\"InternalRef\"\u003e1\u003c/span\u003e)\u003c/p\u003e\u003cp\u003e\u003cb\u003eSample size {14}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eTo determine the minimum required sample size, descriptive statistics from previous studies by Sheikhi et al. [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e] and Gholami et al. [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e] will be utilized in conjunction with the G*Power software (version 3.1.9.2; University of Düsseldorf, Düsseldorf, Germany). A repeated measures analysis of variance (ANOVA) will be employed to assess the interaction effect between group and time, based on a statistical power of 80%, an alpha level of 0.05, a beta of 0.20, and a medium effect size of 0.25. Accordingly, a minimum of 14 participants per group is required. To account for a potential 10% drop-out rate and to enhance statistical power, the final sample size will be increased to 16 participants per group, resulting in a total of 48 participants. This effect size is consistent with improvements observed in hip and knee biomechanics following interventions in previous studies [\u003cspan citationid=\"CR28\" class=\"CitationRef\"\u003e28\u003c/span\u003e, \u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003eRecruitment {15}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eParticipants will be recruited through targeted advertising, direct contact with coaches and university sports teams, and the dissemination of information via virtual platforms. All athletes from Tehran universities in volleyball, futsal, handball, and basketball are invited to participate in this study. Eligible participants will be selected based on predetermined inclusion and exclusion criteria.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAssignment of interventions: allocation\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eSequence generation {16a}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eRandomization will be conducted using a freely accessible web-based tool (\u003cspan class=\"ExternalRef\"\u003e\u003cspan class=\"RefSource\"\u003ehttp://randomizer.org/\u003c/span\u003e\u003cspan address=\"http://randomizer.org/\" targettype=\"URL\" class=\"RefTarget\"\u003e\u003c/span\u003e\u003c/span\u003e, Social Psychology Network, Middletown, CT, USA; accessed on 22 June 2013). An independent researcher will generate the allocation sequence without involvement in the recruitment process. Randomization will be conducted using pre-prepared numbers ranging from 1 to 48, each enclosed in a sealed, opaque envelope and placed in a box to ensure allocation concealment. Participants will be randomly allocated in a 1:1:1 ratio to one of three groups: (1) NLP (n = 16), (2) DL (n = 16), and (3) control (n = 16) [\u003cspan citationid=\"CR34\" class=\"CitationRef\"\u003e34\u003c/span\u003e]. Upon completion of the study, participants will be informed of the group to which they have been assigned for intervention.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConcealment mechanism {16b}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe random numerical sequence was placed in sealed, opaque envelopes and stored in a box to ensure allocation concealment. An independent researcher, blinded to the baseline assessment, opened the envelopes based on group assignment and subsequently conducted the training sessions.\u003c/p\u003e\u003cp\u003e\u003cb\u003eImplementation {16c}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eGroup allocation, participant enrollment, and assignment to intervention groups will be conducted by an independent researcher who is not involved in other aspects of the study. Two sports science professionals, each with a minimum of five years of experience in ACL injury prevention programs, will be present throughout the intervention. They will provide instruction, oversee the correct execution of exercises, and ensure adherence to intervention procedures. They are also familiar with the exercise protocols.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAssignment of interventions: Blinding\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eWho will be blinded? {17a}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe present study will employ a single-blind design, in which only the outcome assessors are blind to their group allocation. Outcome measures are assessed at baseline and post-test by a blinded assessor who remains unaware of both the study hypothesis and methodology.\u003c/p\u003e\u003cp\u003e\u003cb\u003eProcedure for unblinding if needed {17b}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eOur process avoids the identification of information for our participants or group of outcomes from our controlled trial to the participants and/or investigators conducting the study.\u003c/p\u003e\u003cp\u003e\u003cb\u003eData collection and management\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003ePlans for assessment and collection of outcomes {18a}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eKinetic and kinematic data during the single-leg drop vertical jump test will be simultaneously collected using a force plate (Bertec corporation, Columbus, OH), sampling at 1200 Hz, and a motion analysis system (Kestrel 8.0 motion analysis, US), sampling at 240 Hz. Reflective markers will be placed on the iliac crest, ASIS, posterior superior iliac apine (PSIS), greater trochanters, medial and lateral femoral epicondyles, medial and lateral malleolus, 1st and 5th metatarsal heads, and the heel of their shoes. In addition, clusters of four markers attached to rigid shells will be placed on their thighs and legs [\u003cspan citationid=\"CR47\" class=\"CitationRef\"\u003e47\u003c/span\u003e]. The plug-in gait marker set will be employed for motion capture [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. Marker trajectories will be recorded using cortex software (Motion Analysis Corporation, Santa Rosa, CA) and an eight-camera motion analysis system (Eagle cameras; Motion Analysis Corporation).\u003c/p\u003e\u003cp\u003eA static calibration trial will be conducted with the athletes standing in the anatomical position. The marker data will be cut off at a frequency of 15 Hz, while the force data will be cut off at a frequency of 50 Hz. Depending on the type of task and the markers attached to the trunk, pelvis, knees, and ankles, the cameras cover a volume of space in the X, Y, and Z axes of 3×4×2.5, respectively [\u003cspan citationid=\"CR48\" class=\"CitationRef\"\u003e48\u003c/span\u003e]. This results in joint angles of flexion/extension, abduction/adduction, and internal/external rotation. The midpoint between the medial and lateral epicondyles of the femur and the medial and lateral malleolus will be used to estimate the centers of the knee and ankle joints, respectively. The hip joint center will be estimated using a regression method [\u003cspan citationid=\"CR49\" class=\"CitationRef\"\u003e49\u003c/span\u003e]. Joint angles represent the orientation of the distal segment's local coordinate system relative to the proximal segment's [\u003cspan citationid=\"CR50\" class=\"CitationRef\"\u003e50\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eInitial contact and toe-off were identified as the instances when the vertical GRF first exceeded 10 N and subsequently fell below 10 N, respectively, before take-off [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The period from initial contact (vGRF \u0026gt; 10 N) to 100 ms post-initial contact was defined as the landing phase [\u003cspan citationid=\"CR51\" class=\"CitationRef\"\u003e51\u003c/span\u003e]. All joint moments will be reported as external moments and calculated using the inverse dynamics method. Joint moments and vertical GRF will be normalized to body weight. For each participant, the data will be averaged across five successful trials of the single-leg drop vertical jump test. Visual3D software (C-Motion Inc., Rockville, MD, USA) will be used to construct the biomechanical model and analyze the collected data. Data processing will be performed using MATLAB engineering software (version 8.4, 2014b).\u003c/p\u003e\u003cp\u003eBiomechanics during single-leg drop-vertical jump test with neurocognitive load\u003c/p\u003e\u003cp\u003eParticipants will be instructed to stand barefoot on a 30 cm-high box, with their arms in a self-selected position. They will then be directed to perform a single-leg landing onto a force plate positioned 30 cm from the box, immediately followed by a maximal vertical jump and a subsequent landing in the initial position. Each participant will complete five trials, and the mean value of these trials will be used for statistical analysis. Trials will be deemed invalid and repeated if the participant loses balance, falls, makes contact with the ground using the contralateral foot, or performs a jump onto the box instead of a landing. To minimize the effects of fatigue, a one-minute rest interval will be provided between each trial [\u003cspan citationid=\"CR52\" class=\"CitationRef\"\u003e52\u003c/span\u003e]. The dominant leg is defined as the leg that the participant prefers to use to land after a jump [\u003cspan citationid=\"CR27\" class=\"CitationRef\"\u003e27\u003c/span\u003e]. The single-leg drop vertical jump test has demonstrated good reliability. It has reported intraclass correlation coefficients (ICC ≤ 0.75) [\u003cspan citationid=\"CR53\" class=\"CitationRef\"\u003e53\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eNeurocognitive load\u003c/p\u003e\u003cp\u003eThe Stroop effect is a cognitive task commonly employed to impose cognitive load during jumping and landing assessments. An examiner stands approximately three meters in front of the participant, at eye level, and presents a series of color words (e.g., blue, red, black, yellow). Each word is displayed in a font color that either matches or conflicts with the semantic meaning of the word, thereby eliciting the Stroop effect. Participants will be instructed to respond to the font color of the word, rather than its semantic content, upon landing. Trials in which participants provide an incorrect response to the color will be considered invalid and repeated. The Stroop effect represents a form of cognitive interference that affects reaction time and has been shown to increase response latency compared to tasks without such interference [\u003cspan citationid=\"CR54\" class=\"CitationRef\"\u003e54\u003c/span\u003e]. The Stroop task will serve as the cognitive load imposed on participants during the execution of functional performance and single-leg drop vertical jump tests. The inclusion of this cognitive component is intended to enhance the ecological validity and generalizability of the assessments by simulating the cognitive demands commonly encountered in real-world athletic environments.\u003c/p\u003e\u003cp\u003eTuck jump test\u003c/p\u003e\u003cp\u003eThe tuck jump test will be used to identify athletes at high risk for ACL injury and to assess functional performance. This test is a practical and effective motor assessment tool designed to identify neuromuscular deficits related to ACL injury, particularly in landing technique during repetitive plyometric activity. Excellent reliability was demonstrated, with ICC values ranging from 0.94 to 0.96, [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. This test requires participants to perform continuous maximal height jumps for 10 seconds within a predefined spatial range. The scoring system comprises ten quantitative dual-item measures, which collectively evaluate neuromuscular impairments across four domains: ligament dominance, quadriceps dominance, trunk dominance, and leg dominance. Additionally, the test facilitates the assessment of fatigue effects and deficits in feedforward and predictive neuromuscular responses [\u003cspan citationid=\"CR36\" class=\"CitationRef\"\u003e36\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eParticipants will be instructed to position their feet at the center of a marked rectangle on the floor, which is composed of four smaller rectangles, each measuring 41 cm in length and 35 cm in width. Before the test, standardized instructions will be provided, detailing the procedure, including the requirement to raise the knees to hip height and to attempt landing within the center of the marked rectangle with the feet positioned shoulder-width apart. To identify anatomical landmarks in two-dimensional kinematic analysis, reflective markers will be placed on the following anatomical locations: the acromioclavicular joint, sternum, anterior superior iliac spine (ASIS), greater trochanter of the femur, medial and lateral epicondyles of the femur, medial and lateral malleoli of the ankle, as well as the first and fifth metatarsal heads. During each trial, performance will be recorded using two video cameras (Galaxy A12, SM-A127F/DS) positioned in the frontal and sagittal planes, each placed at a distance of 3 meters from the participant and aligned with waist height.\u003c/p\u003e\u003cp\u003eTo ensure accurate identification of movement errors, participants will wear minimal clothing necessary for appropriate video analysis. Following the test, all recorded trials will be analyzed using Kinovea software (Kinovea, version 0.8.15, USA), through which any biomechanical deficits exhibited during jumping and landing will be systematically evaluated and scored. According to Dingenen et al., 2D kinematic analysis (ICC = 0.90–0.99) and kinovea software have demonstrated high reliability [\u003cspan citationid=\"CR55\" class=\"CitationRef\"\u003e55\u003c/span\u003e]. The scoring system is designed such that participants are assigned a score of “one” or “two” if they fail to meet the specified performance criteria, with the score reflecting the severity of the observed defect. A score of “zero” is assigned when the performance criteria are satisfactorily met. A movement pattern is deemed ineffective if an associated technical deficiency is observed at least twice within the ten-second testing period [\u003cspan citationid=\"CR56\" class=\"CitationRef\"\u003e56\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSingle-leg triple crossover-hop for distance test\u003c/p\u003e\u003cp\u003eTo perform the test, the athlete begins by standing on the dominant leg behind a designated starting line. The task involves executing three consecutive maximal forward jumps, while alternately zigzagging to the left and right across a 15 cm-wide strip on the ground, without making contact with the strip. On the third and final jump, the athlete is required to stabilize and maintain the landing position for two seconds. The jump distance will be measured from the starting line to the heel of the landing foot and recorded as the participant's performance. If the participant loses balance, makes ground contact with the non-dominant foot, or performs an additional jump, the trial will be deemed invalid and subsequently repeated. The single-leg triple crossover hop for distance test has demonstrated excellent validity, with ICC values ranging from 0.89 to 0.99, [\u003cspan citationid=\"CR57\" class=\"CitationRef\"\u003e57\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eThe 90 medial-rotation hop for distance test\u003c/p\u003e\u003cp\u003eParticipants will be instructed to stand on the dominant leg with the medial aspect of the foot perpendicular to the intended jump direction. They should execute the jump with approximately 90 degrees of internal rotation in the transverse plane during the forward phase. Before takeoff, the foot should not be aligned with the intended direction of the jump. However, upon landing, the foot should be oriented in the direction of the jump. The examiner will visually assess and verify this alignment. If the participant fails to land in alignment with the direction of the jump, defined as a deviation greater than 10 degrees, the trial will be considered invalid and will be repeated. The jump distance will be measured from the medial aspect of the foot at take-off to the tip of the toes at landing. The 90° medial rotation hop for the distance test has demonstrated excellent test-retest reliability (ICC = 0.93–0.98) [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e].\u003c/p\u003e\u003cp\u003eSingle-leg medial side triple hop for distance test\u003c/p\u003e\u003cp\u003eParticipants will be instructed to stand on their dominant leg with the medial side of their foot perpendicular to the intended direction of their hop. They will then perform three consecutive medial hops, landing on the same foot each time. Upon the final landing, the foot must remain perpendicular to the intended direction of the hop. The total hop distance will be measured from the medial aspect of the foot at initial takeoff to the medial aspect of the foot at final landing. The trial will be deemed invalid and repeated if the participant is unable to maintain balance for at least two seconds after landing, touches the ground with their upper limbs or contralateral leg, or takes additional small jumps after landing. A 30-second rest period will be provided between each attempt. The single-leg medial side triple hop for the distance test has shown excellent reliability when tested repeatedly (ICC = 0.93–0.98) [\u003cspan citationid=\"CR46\" class=\"CitationRef\"\u003e46\u003c/span\u003e].\u003c/p\u003e\u003cp\u003e\u003cb\u003ePlans to promote participant retention and complete follow‑up {18b}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe researcher will monitor each participant's adherence to the prescribed exercise protocol through regular phone calls, email correspondence, and in-person meetings. To further motivate participants, a small gift will be provided upon completion of the study. In addition, we count on the commitment of the athletic trainers to ensure that it can be carried out in the most correct way possible.\u003c/p\u003e\u003cp\u003e\u003cb\u003eData management {19}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eAll collected data will be coded using numerical identifiers to ensure participant anonymity. Additionally, the data will be disseminated through two primary channels: publication in academic papers and submission to a trial registration website.\u003c/p\u003e\u003cp\u003e\u003cb\u003eConfidentiality {27}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe data sheets and electronic files that have been collected will not contain any personal information, and each participant will be given a unique study code.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePlans for collection, laboratory evaluation, and storage of biological specimens for genetic or molecular analysis in this trial/future use {33}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThis study did not include the collection of biological specimens from participants.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStatistical methods\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eStatistical methods for primary and secondary outcomes {20a}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eData distribution normality and variance homogeneity will be assessed using the Shapiro-Wilk and Levene's tests, respectively. Parametric tests were applied when normality assumptions were met; otherwise, nonparametric alternatives were used. A 3×2 repeated measures ANOVA test will be performed to determine the differences between the three groups (control, DL, and NLP) and time (pre-test and post-test). Then, post hoc comparisons with a Bonferroni correction will be performed. If the assumption of sphericity is violated (as evidenced by unequal variances between paired measurement groups), the Greenhouse-Geisser correction will be applied. The pretest-to-posttest within-group factor will be considered the main effect of time, and the between-group factor will be considered the main effect of group. The percentage change from pretest to posttest will be calculated. Partial eta squared (ηp²) will compute effect sizes (ES) to enhance statistical power. The effect size will be classified as small (0.01), medium (0.06), or large (0.14) [\u003cspan citationid=\"CR39\" class=\"CitationRef\"\u003e39\u003c/span\u003e]. Statistical analyses will be performed at a 95% confidence level (p \u0026lt; 0.05) using IBM SPSS statistics software, version 26 (IBM Corp., Armonk, NY, USA).\u003c/p\u003e\u003cp\u003e\u003cb\u003eInterim analyses {21b}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe principal investigator will have access to the interim results and will make the final decision about whether to terminate the trial.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods for additional analyses (e.g., subgroup analyses) {20b}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eFor subgroup analyses, participants’ demographic characteristics (e.g., number of athletes, age, body mass, height, body mass index, sports experience, and sport type) will be compared using a one-way analysis of variance (ANOVA). If the omnibus test yields a significant result, post hoc independent t-tests will be conducted.\u003c/p\u003e\u003cp\u003e\u003cb\u003eMethods in analysis to handle protocol non‑adherence and any statistical methods to handle missing data {20c}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eParticipant adherence to the intervention will be monitored by recording attendance at each session. Participants who miss more than three consecutive sessions, whether due to injury or other reasons, will be classified as having not completed the intervention. To mitigate the risk of noncompliance with the study protocol, the sample size will be increased by 10%. However, if nonadherence persists, the intention-to-treat (ITT) analysis will be applied. In cases of missing data, the multiple imputation method will be used to address the gaps appropriately.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePlans to give access to the full protocol, participant‑level data, and statistical code {31c}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe study protocol will be published in the journal, and the corresponding author may be contacted if you would like access to the underlying data.\u003c/p\u003e\u003cp\u003e\u003cb\u003eOversight and monitoring\u003c/b\u003e\u003c/p\u003e\u003cp\u003e\u003cb\u003eComposition of the coordinating center and trial steering Committee {5d}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe study does not comprise a steering committee, management team, or oversight body beyond the lead author and the protocol contributor.\u003c/p\u003e\u003cp\u003e\u003cb\u003eComposition of the data monitoring committee, its role, and reporting structure {21a}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe data monitoring committee will consist of researchers who have no competing interests in this study. Committee members will periodically evaluate participants and make relevant recommendations.\u003c/p\u003e\u003cp\u003e\u003cb\u003eAdverse event reporting and harms {22}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eA dedicated group will use a communication platform to facilitate the collection, assessment, reporting, and management of both solicited and self-reported adverse events and other undesirable effects related to the interventions or trial conduct. Participants will be encouraged to report their conditions through the platform.\u003c/p\u003e\u003cp\u003e\u003cb\u003eFrequency and plans for auditing trial conduct {23}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eA detailed timetable for implementation will be included in the protocol, and a checklist will be used to track the completion of each item.\u003c/p\u003e\u003cp\u003e\u003cb\u003ePlans for communicating important protocol amendments to relevant parties (e.g., trial participants, ethical committees) {25}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eShould any substantial amendments to the protocol be made, the relevant parties will be apprised of them via notifications on the WhatsApp messaging platform. Additionally, any potential amendments to the protocol will be communicated to the Ministry of Health via the IRCT website.\u003c/p\u003e\u003cp\u003e\u003cb\u003eDissemination plans {31a}\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe research findings will be disseminated to study participants, healthcare practitioners, and the broader public via peer-reviewed scientific journals and publicly accessible results databases.\u003c/p\u003e"},{"header":"Discussion","content":"\u003cp\u003e\u003cb\u003eFuture expectations of the study\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThis study designed a randomized controlled trial protocol to compare the effects of plyometric training based on DL and NLP approaches on biomechanical and functional outcomes in athletes at high risk for an ACL injury. The main research question investigates whether variability-based training (integrating NLP and DL with plyometrics) improves functional performance and landing biomechanics in high-risk ACL athletes compared to a control group. This field-based controlled trial is expected to advance ACL injury risk reduction programs by decreasing injury likelihood and refining return-to-sport criteria. By integrating sport-specific physical and cognitive indicators, this study aims to improve ecological validity and generalizability, better reflecting the multifaceted demands of athletic performance. The findings may inform enhanced rehabilitation protocols, injury risk reduction, and optimize ACL injury prevention strategies. To facilitate knowledge translation, findings will be disseminated through workshops for athletic trainers and sports medicine practitioners, alongside presentations at scientific conferences and forums. Although neuromuscular and biomechanical differences exist between sexes, females exhibit greater knee valgus, reduced flexion at initial contact, and stiffer landings that are consistently associated with higher ACL injury risk [\u003cspan citationid=\"CR58\" class=\"CitationRef\"\u003e58\u003c/span\u003e]. The current intervention protocol is hypothesized to reduce ACL injury incidence in high-risk female athlete populations through the modification of landing biomechanics toward safer movement patterns.\u003c/p\u003e\u003cp\u003e\u003cb\u003eLimitations\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThis study has several limitations. First, the sample was restricted to male athletes, limiting the generalizability of the findings to female athletes. Second, the study did not include an electromyographic analysis of lower-limb muscle activity, which could have provided valuable insights into the neuromuscular mechanisms underlying landing biomechanics. Third, the absence of a comparison group that only received plyometric training limits the ability to determine whether the observed effects in the intervention groups were due to the variability-based approaches (NLP and DL) or the plyometric training itself. Fourth, the predominance of athletes recruited from a single center may introduce bias and limit the generalizability of the findings. Fifth, laboratory-based biomechanical assessments, even those incorporating cognitive tasks like the Stroop test, still differ from in-game dynamics.\u003c/p\u003e\u003cp\u003e\u003cb\u003eStrengths\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThe study has high ecological validity via neurocognitive load. Given that the present study integrates two ACL injury prevention training protocols previously shown to have large effect sizes, the resulting intervention may serve as an effective and ecologically valid training program for enhancing injury prevention strategies and reducing injury risk among athletes participating in indoor ball sports. If the results are favorable, the proposed training protocol could provide physiotherapists, coaches, and sports science professionals with a practical framework for guiding injury prevention strategies and facilitating a safe and effective return to sports.\u003c/p\u003e\u003cp\u003e\u003cb\u003eTrial status\u003c/b\u003e\u003c/p\u003e\u003cp\u003eThis trial was prospectively registered in the IRCT on 15 March 2025 (Registration Code: IRCT20210602051477N3). The recruitment of participants will take place from September to October 2025.\u003c/p\u003e"},{"header":"Abbreviations","content":"\u003cdiv class=\"DefinitionList\"\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eACL\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eAnterior cruciate ligament\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eNLP\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eNon-linear pedagogy\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003cdiv class=\"DefinitionListEntry\"\u003e\u003cdiv class=\"Term\"\u003eDL\u003c/div\u003e\u003cdiv class=\"Description\"\u003e\u003cp\u003eDifferential learning.\u003c/p\u003e\u003c/div\u003e\u003c/div\u003e\u003c/div\u003e"},{"header":"Declarations","content":"\u003cp\u003e\u003cstrong\u003eAcknowledgements\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eNot applicable.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAuthors’ contributions {31b}\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eMHG serves as the chief investigator and guarantor of the study; he conceived the research idea and led the development of the study proposal and protocol. MHN, HS, MKT, and AB contributed to the study design and the formulation of the proposal. All authors reviewed and approved the final manuscript.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eFunding {4}\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they did not receive any funding from public, commercial, or nonprofit agencies to conduct this research.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eAvailability of data and materials {29}\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eUpon publication in this journal, the final test dataset will be made publicly available to all readers.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eEthics approval and consent to participate\u003c/strong\u003e \u003cstrong\u003e{24}\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThis study received ethical approval from the biomedical research ethics committee of Kharazmi University\u0026nbsp;(Approval Code:\u0026nbsp;IR.KHU.REC.1403.169). Additionally, the trial was prospectively registered on the\u0026nbsp;IRCT\u0026nbsp;(Registration Code:\u0026nbsp;IRCT20210602051477N3). Written informed consent will be obtained from all eligible participants before their inclusion in the study.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eConsent for publication {32}\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eAll of the authors have consented to the publication of this work.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eCompeting\u003c/strong\u003e \u003cstrong\u003einterests {28}\u003c/strong\u003e\u003c/p\u003e\n\u003cp\u003eThe authors declare that they have no financial or personal relationships with any individuals or organizations that could have inappropriately influenced the conduct or reporting of this study.\u003c/p\u003e"},{"header":"References","content":"\u003col\u003e\u003cli\u003e\u003cspan\u003eNessler T, Denney L, Sampley J. ACL injury prevention: what does research tell us? 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Elsevier; 2019. pp. 532\u0026ndash;5.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSanders TL, Maradit Kremers H, Bryan AJ, Larson DR, Dahm DL, Levy BA, et al. Incidence of anterior cruciate ligament tears and reconstruction: a 21-year population-based study. Am J Sports Med. 2016;44(6):1502\u0026ndash;7.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eSheikhi B, Letafatkar A, Thomas AC, Ford KR. Altered trunk and lower extremity movement coordination after neuromuscular training with and without external focus instruction: A randomized controlled trial. BMC Sports Sci Med Rehabilitation. 2021;13(1):1\u0026ndash;9.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eF\u0026auml;ltstr\u0026ouml;m A, H\u0026auml;gglund M, Hedevik H, Kvist J. Poor validity of functional performance tests to predict knee injury in female soccer players with or without anterior cruciate ligament reconstruction. Am J Sports Med. 2021;49(6):1441\u0026ndash;50.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eMyer GD, Ford KR, Hewett TE. Tuck jump assessment for reducing anterior cruciate ligament injury risk. Athletic therapy today: J sports health care professionals. 2008;13(5):39.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eTaylor JB, Nguyen A-D, Shultz SJ, Ford KR. Hip biomechanics differ in responders and non-responders to an ACL injury prevention program. Volume 28. Arthroscopy: Knee Surgery, Sports Traumatology; 2020. pp. 1236\u0026ndash;45.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eNess BM, Zimney K, Kernozek T, Schweinle WE, Schweinle A. Incorporating a dual-task assessment protocol with functional hop testing. Int J sports Phys therapy. 2020;15(3):407.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eHamoongard M, Hadadnezhad M, Abbasi A. 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Phys Ther Sport. 2018;29:84\u0026ndash;92.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eFort-Vanmeerhaeghe A, Montalvo AM, Lloyd RS, Read P, Myer GD. Intra-and inter-rater reliability of the modified tuck jump assessment. J sports Sci Med. 2017;16(1):117.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003eEbert JR, Du Preez L, Furzer B, Edwards P, Joss B. Which hop tests can best identify functional limb asymmetry in patients 9\u0026ndash;12 months after anterior cruciate ligament reconstruction employing a hamstrings tendon autograft? Int J sports Phys therapy. 2021;16(2):393.\u003c/span\u003e\u003c/li\u003e\u003cli\u003e\u003cspan\u003ePark-Braswell K, Grooms D, Shultz S, Raisbeck L, Rhea C, Schmitz R. Sex-Specific Brain Activations during Single-Leg Exercise. Int J Sports Phys Therapy. 2022;17(7):1249.\u003c/span\u003e\u003c/li\u003e\u003c/ol\u003e"}],"fulltextSource":"","fullText":"","funders":[],"hasAdminPriorityOnWorkflow":false,"hasManuscriptDocX":true,"hasOptedInToPreprint":true,"hasPassedJournalQc":"","hasAnyPriority":false,"hideJournal":false,"highlight":"","institution":"","isAcceptedByJournal":true,"isAuthorSuppliedPdf":false,"isDeskRejected":"","isHiddenFromSearch":false,"isInQc":false,"isInWorkflow":false,"isPdf":false,"isPdfUpToDate":true,"isWithdrawnOrRetracted":false,"journal":{"display":true,"email":"[email protected]","identity":"trials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"trls","sideBox":"Learn more about [Trials](http://trialsjournal.biomedcentral.com/)","snPcode":"13063","submissionUrl":"https://www.editorialmanager.com/trls","title":"Trials","twitterHandle":"MedicalEvidence","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true},"keywords":"ACL injury risk research, Plyometric training, Motor learning strategy, Ecological constraints, Nonlinear dynamics","lastPublishedDoi":"10.21203/rs.3.rs-7114294/v1","lastPublishedDoiUrl":"https://doi.org/10.21203/rs.3.rs-7114294/v1","license":{"name":"CC BY 4.0","url":"https://creativecommons.org/licenses/by/4.0/"},"manuscriptAbstract":"\u003cp\u003e\u003cstrong\u003eBackground: \u003c/strong\u003eThe 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.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eMethods: \u003c/strong\u003eThis 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.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eDiscussion: \u003c/strong\u003eThis 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.\u003c/p\u003e\n\u003cp\u003e\u003cstrong\u003eTrial registration: \u003c/strong\u003eThe 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).\u003c/p\u003e","manuscriptTitle":"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","msid":"","msnumber":"","nonDraftVersions":[{"code":1,"date":"2025-08-22 10:33:21","doi":"10.21203/rs.3.rs-7114294/v1","editorialEvents":[{"type":"communityComments","content":0},{"type":"decision","content":"Accept","date":"2026-02-08T08:31:36+00:00","index":"","fulltext":""},{"type":"reviewerAgreed","content":"","date":"2026-01-08T09:46:52+00:00","index":0,"fulltext":""},{"type":"reviewersInvited","content":"","date":"2025-08-15T05:08:04+00:00","index":"","fulltext":""},{"type":"editorAssigned","content":"","date":"2025-08-11T07:00:00+00:00","index":"","fulltext":""},{"type":"submitted","content":"Trials","date":"2025-07-26T02:53:26+00:00","index":"","fulltext":""}],"status":"published","journal":{"display":true,"email":"[email protected]","identity":"trials","isNatureJournal":false,"hasQc":true,"allowDirectSubmit":false,"externalIdentity":"trls","sideBox":"Learn more about [Trials](http://trialsjournal.biomedcentral.com/)","snPcode":"13063","submissionUrl":"https://www.editorialmanager.com/trls","title":"Trials","twitterHandle":"MedicalEvidence","acdcEnabled":true,"dfaEnabled":true,"editorialSystem":"em","reportingPortfolio":"BMC/SO AJ","inReviewEnabled":true,"inReviewRevisionsEnabled":true}}],"origin":"","ownerIdentity":"36156795-4c54-4ac9-8448-aead5721a903","owner":[],"postedDate":"August 22nd, 2025","published":true,"recentEditorialEvents":[],"rejectedJournal":[],"revision":"","amendment":"","status":"published-in-journal","subjectAreas":[],"tags":[],"updatedAt":"2026-02-23T16:03:04+00:00","versionOfRecord":{"articleIdentity":"rs-7114294","link":"https://doi.org/10.1186/s13063-026-09555-0","journal":{"identity":"trials","isVorOnly":false,"title":"Trials"},"publishedOn":"2026-02-17 15:59:26","publishedOnDateReadable":"February 17th, 2026"},"versionCreatedAt":"2025-08-22 10:33:21","video":"","vorDoi":"10.1186/s13063-026-09555-0","vorDoiUrl":"https://doi.org/10.1186/s13063-026-09555-0","workflowStages":[]},"version":"v1","identity":"rs-7114294","journalConfig":"researchsquare"},"__N_SSP":true},"page":"/article/[identity]/[[...version]]","query":{"redirect":"/article/rs-7114294","identity":"rs-7114294","version":["v1"]},"buildId":"8U1c8b4HqxoKbykW_rLl7","isFallback":false,"isExperimentalCompile":false,"dynamicIds":[84888],"gssp":true,"scriptLoader":[]}