Motor imagery is a cognitive technique in which individuals mentally rehearse a movement without physically performing it. However, individuals with low imagery ability may not fully benefit from traditional motor imagery training. Virtual reality (VR) may enhance imagery vividness by providing immersive visual feedback. The purpose of this study is to compare the effects of immersive VR-based motor imagery, action observation combined with motor imagery, kinesthetic motor imagery alone, and a control condition on imagery ability, muscle strength, and muscle activation. Thirty-two healthy male participants will be assigned to one of four parallel groups based on imagery ability levels. All participants will complete a 4-week unilateral leg extension resistance training program (three sessions per week at 80% of one-repetition maximum). During each session, participants will perform their assigned imagery protocol. Primary outcomes include changes in imagery ability assessed by the Movement Imagery Questionnaire-3. Secondary outcomes include isokinetic quadriceps peak torque, average power, and surface electromyography activity of the rectus femoris, vastus medialis, and vastus lateralis muscles. The findings of this study may provide insight into whether immersive VR can enhance the effectiveness of motor imagery training in individuals with low imagery ability.

Motor imagery training has been shown to enhance motor performance and strength adaptations; however, its effectiveness is strongly influenced by individual imagery ability. Individuals with low imagery ability may experience limited benefits due to reduced vividness and sensory engagement during mental rehearsal. Immersive virtual reality (VR) may enhance the perceptual and sensory components of imagery by providing first-person visual feedback, thereby potentially improving motor-related neural activation and training adaptations. This study is designed as a 4-week, parallel-group interventional trial including healthy young adult males. Participants will be categorized according to imagery ability assessed by the Movement Imagery Questionnaire-3 (MIQ-3) and allocated into four groups: immersive VR-based motor imagery, action observation combined with motor imagery, kinesthetic motor imagery alone, and a control condition involving relaxation imagery. All participants will complete a supervised unilateral leg extension resistance training program performed three times per week at 80% of one-repetition maximum. Each session will consist of four sets of 8-12 repetitions for the dominant leg. Imagery interventions will be administered prior to each training session according to group assignment. Isokinetic strength assessments will be performed at angular velocities of 60°/s and 120°/s. Surface electromyography (sEMG) signals will be recorded from the rectus femoris, vastus medialis, and vastus lateralis muscles during testing. Imagery ability will be reassessed following the intervention period. The primary objective of the study is to determine whether immersive VR-based motor imagery enhances imagery ability and neuromuscular adaptations compared to traditional motor imagery approaches and control conditions.

Inclusion Criteria:

• Healthy male individuals aged 18-30 years No participation in a structured lower-limb resistance training program within the previous 6 months No prior experience with structured motor imagery training Provided written informed consent

Exclusion Criteria:

• History of lower-limb musculoskeletal injury or surgery within the past 6 months Neurological disorders affecting motor control Visual or vestibular impairments preventing safe use of virtual reality equipment Current use of medications affecting neuromuscular performance Any medical condition contraindicating resistance training

Eligible participants must be biologically male and self-identify as male.

De-identified individual participant data (IPD) underlying the primary and secondary outcome measures, including MIQ-3 scores, isokinetic peak torque values, average power, and normalized sEMG data, will be shared. Demographic variables necessary for replication (age and body mass) will also be included.

Data will be available beginning 6 months following publication of the primary results and will remain available for 5 years.

Access to de-identified individual participant data will be granted to qualified researchers upon reasonable request to the corresponding author. Requests must include a brief research proposal outlining the intended use of the data. Data will be shared following approval by the study investigators and in accordance with institutional and ethical guidelines.