Effects of Virtual Reality-Based Optokinetic Stimulation on Landing Technique and Dynamic Knee Valgus in Athletes

Participants will complete a single session of drop vertical jump training consisting of two blocks of 10 repetitions, with 30 seconds of rest between repetitions and five minutes between blocks. Performance feedback will be provided after each block. Seated virtual reality-based optokinetic stimulation will be administered before each training block, consisting of three 60-second exposures in each direction, totaling six minutes of active stimulation per block

Following a standardized warm-up and task familiarization, participants will perform two blocks of 10 drop vertical jumps from a 30-cm box toward a target positioned at 50% of their height. After landing on both feet, participants will immediately jump as high and forward as possible and maintain the final landing position for five seconds. Rest periods will be 30 seconds between repetitions and five minutes between blocks. Feedback based on real-time landing error scores will be provided after each block.

Optokinetic stimulation will be delivered through a Meta Quest 3S headset while participants sit in a supported chair with their feet on the floor. Participants will track a red balloon with their eyes while keeping their head as still as possible. Foreground stimuli will move at 30 degrees per second, with the background moving in the opposite direction at twice that speed. Three 60-second exposures will be delivered in each direction before each training block, with 30-60-second rest periods. Active stimulation will total six minutes per block and 12 minutes across the session, excluding rest. The headset will be removed before jump training.

Participants will complete the same single-session drop vertical jump training as the experimental group, consisting of two blocks of 10 repetitions, with 30 seconds of rest between repetitions and five minutes between blocks. Performance feedback will be provided after each block. No additional optokinetic stimulation will be administered before the training blocks.

Following a standardized warm-up and task familiarization, participants will perform two blocks of 10 drop vertical jumps from a 30-cm box toward a target positioned at 50% of their height. After landing on both feet, participants will immediately jump as high and forward as possible and maintain the final landing position for five seconds. Rest periods will be 30 seconds between repetitions and five minutes between blocks. Feedback based on real-time landing error scores will be provided after each block.

Landing technique will be assessed using the 17-item Landing Error Scoring System (LESS) from frontal and sagittal video recordings of the drop vertical jump task. Total scores range from 0 to 19 points, with higher scores indicating more landing errors and poorer landing technique. Participants will complete five successful trials at each assessment, and the mean total score across these five trials will be used for analysis. Assessments will be performed by an assessor blinded to group allocation. Changes over time will be compared between groups.

Dynamic knee valgus will be assessed using two-dimensional frontal-plane video analysis during a single-leg squat on the dominant limb. The frontal plane projection angle (FPPA), expressed in degrees, will be measured at the deepest squat position using lines connecting the anterior superior iliac spine, the midpoint of the patella, and the midpoint of the ankle joint. The mean of three successful repetitions will be used for analysis. Changes over time will be compared between groups by an assessor blinded to group allocation.Assessments will be performed by an assessor blinded to group allocation. Changes over time will be compared between groups.