Effects of Virtual Reality-Based Optokinetic Stimulation Added to Neuromuscular Training in Basketball Players

Participants will continue their usual basketball team training for six weeks. No additional neuromuscular training or virtual reality-based optokinetic stimulation will be provided as part of the study.

Participants will continue their usual basketball team training and additionally receive supervised neuromuscular training three times per week for six weeks, totaling 18 sessions. Each session will last approximately 25-30 minutes and include progressively advanced strength, balance, proximal control, and plyometric exercises targeting jump-landing mechanics.

Supervised neuromuscular training will be delivered three times per week for six weeks (18 sessions), in addition to usual basketball team training. Each session will last approximately 25-30 minutes and include strength, balance, proximal control, and plyometric exercises. Exercises will progress from bilateral squats, walking lunges, single-leg balance, and drop landings to single-leg squats, drop jumps, single-leg countermovement jumps, and single-leg standing long jumps. Exercises will be performed in 3-4 sets, with 60-90 seconds of rest between sets. Exercise difficulty and repetitions will progress according to the weekly protocol.

• TNM

Participants will continue their usual basketball team training and receive the same supervised neuromuscular training program as the active comparator group, three times per week for six weeks, totaling 18 sessions. Immediately before each neuromuscular training session, participants will receive virtual reality-based optokinetic stimulation. Visual stimulus speed, exposure duration, and postural difficulty will increase progressively over the six-week intervention.

Supervised neuromuscular training will be delivered three times per week for six weeks (18 sessions), in addition to usual basketball team training. Each session will last approximately 25-30 minutes and include strength, balance, proximal control, and plyometric exercises. Exercises will progress from bilateral squats, walking lunges, single-leg balance, and drop landings to single-leg squats, drop jumps, single-leg countermovement jumps, and single-leg standing long jumps. Exercises will be performed in 3-4 sets, with 60-90 seconds of rest between sets. Exercise difficulty and repetitions will progress according to the weekly protocol.

• TNM

Optokinetic stimulation will be delivered using a Meta Quest 3S headset and custom Unity software immediately before neuromuscular training, three times per week for six weeks. Participants will track moving balloons with their eyes while keeping their head and trunk as still as possible. Weekly progression will be: week 1, seated, 20 degrees/s, 3 x 30 s; week 2, standing with feet together, 20 degrees/s, 3 x 60 s; week 3, semi-tandem stance, 30 degrees/s, 3 x 90 s; week 4, tandem stance, 40 degrees/s, 3 x 120 s; week 5, tandem stance, 50 degrees/s, 3 x 150 s; week 6, tandem stance, 60 degrees/s, 3 x 180 s. Clockwise and counterclockwise motion will be presented for equal durations. Background rotation speed will be twice the balloon speed. Symptoms will be monitored using the Simulator Sickness Questionnaire, with exposure adjusted according to tolerance.

• VR-OKS

Peak knee flexion angle of the dominant limb will be measured in degrees using the Xsens MVN Awinda inertial motion capture system during a standardized drop vertical jump from a 30-cm box. The peak angle will be identified during the landing deceleration phase, from initial ground contact to maximum knee flexion. Initial contact will be determined using synchronized force-platform data. The dominant limb will be defined as the preferred leg for kicking a ball. Three successful trials will be recorded at each assessment. Change from baseline to the end of the six-week intervention will be evaluated.

Peak vertical ground reaction force will be measured using a Bertec force platform sampling at 1000 Hz during the standardized drop vertical jump. Initial contact will be defined as the first instant at which filtered vertical ground reaction force exceeds 10 N. Peak force will be identified as the maximum vertical ground reaction force within the first 0.20 seconds after initial contact and normalized to body weight, expressed in multiples of body weight. Three successful trials will be recorded at each assessment. Change from baseline to the end of the six-week intervention will be evaluated.

The time interval between initial ground contact and peak vertical ground reaction force will be measured in seconds using a Bertec force platform sampling at 1000 Hz during the standardized drop vertical jump. Initial contact will be defined as the first instant at which filtered vertical ground reaction force exceeds 10 N. Peak vertical ground reaction force will be identified within the first 0.20 seconds after initial contact. Three successful trials will be recorded at each assessment. Change from baseline to the end of the six-week intervention will be evaluated.

Landing load absorption duration will be measured in seconds as the time interval between peak vertical ground reaction force and maximum knee flexion of the dominant limb during the standardized drop vertical jump. Peak vertical ground reaction force will be identified within the first 0.20 seconds after initial contact using a Bertec force platform. Maximum knee flexion will be identified using synchronized Xsens MVN Awinda motion capture data. The dominant limb will be defined as the preferred leg for kicking a ball. Three successful trials will be recorded at each assessment. Change from baseline to the end of the six-week intervention will be evaluated.

Hip flexion range of motion will be measured in degrees using the Xsens MVN Awinda system, from initial ground contact to the instant of maximum dominant-knee flexion during the standardized drop vertical jump. Bilateral measurements will be calculated within the same analysis window.

Knee flexion range of motion will be measured in degrees using the Xsens MVN Awinda system, from initial ground contact to the instant of maximum dominant-knee flexion during the standardized drop vertical jump. Bilateral measurements will be calculated within the same analysis window.

Ankle dorsiflexion range of motion will be measured in degrees using the Xsens MVN Awinda system, from initial ground contact to the instant of maximum dominant-knee flexion during the standardized drop vertical jump. Bilateral measurements will be calculated within the same analysis window.

The interval from initial ground contact to maximum knee flexion of the dominant limb will be measured in seconds using synchronized Bertec force-platform and Xsens MVN Awinda data during the standardized drop vertical jump.

Peak dominant-knee valgus angle will be measured in degrees using the Xsens MVN Awinda system during the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Valgus will be defined as the maximum positive value of the dominant-knee abduction/adduction angle.

Peak resultant tibial acceleration will be calculated from the three-axis free-acceleration signals of the lower-leg sensors of the Xsens MVN Awinda system during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Acceleration will be expressed in meters per second squared.

Visual dependence will be assessed using the ratio of eyes-closed to eyes-open center-of-pressure sway area measured with a Bertec force platform during tandem stance. Two 30-second trials will be performed under each condition. The ratio is dimensionless, with higher values indicating greater reliance on vision for postural control.

Visual dependence will be assessed using the ratio of eyes-closed to eyes-open mean center-of-pressure velocity measured with a Bertec force platform during tandem stance. Two 30-second trials will be performed under each condition. The ratio is dimensionless, with higher values indicating greater reliance on vision for postural control.

Center-of-pressure sway area will be measured using a Bertec force platform during tandem stance with eyes open and eyes closed. Two 30-second trials will be performed under each condition. Results will be reported separately for each visual condition in square centimeters.

Total center-of-pressure path length will be measured using a Bertec force platform during tandem stance with eyes open and eyes closed. Two 30-second trials will be performed under each condition. Results will be reported separately for each visual condition in centimeters.

Mean center-of-pressure velocity will be measured using a Bertec force platform during tandem stance with eyes open and eyes closed. Two 30-second trials will be performed under each condition. Results will be reported separately for each visual condition in centimeters per second.

Peak anterior-posterior center-of-mass velocity will be obtained from Xsens MVN Awinda data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Velocity will be expressed in meters per second.

Peak medial-lateral center-of-mass velocity will be obtained from Xsens MVN Awinda data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Velocity will be expressed in meters per second.

Peak vertical center-of-mass velocity will be obtained from Xsens MVN Awinda data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Velocity will be expressed in meters per second.

Peak anterior-posterior center-of-mass acceleration will be obtained from Xsens MVN Awinda data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Acceleration will be expressed in meters per second squared.

Peak medial-lateral center-of-mass acceleration will be obtained from Xsens MVN Awinda data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Acceleration will be expressed in meters per second squared.

Peak vertical center-of-mass acceleration will be obtained from Xsens MVN Awinda data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Acceleration will be expressed in meters per second squared.

Anterior-posterior center-of-mass displacement will be calculated from Xsens MVN Awinda position data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Displacement will be expressed in meters.

Medial-lateral center-of-mass displacement will be calculated from Xsens MVN Awinda position data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Displacement will be expressed in meters.

Vertical center-of-mass displacement will be calculated from Xsens MVN Awinda position data during landing load absorption, defined as the interval from peak vertical ground reaction force to maximum dominant-knee flexion. Displacement will be expressed in meters.

Peak dominant-knee flexion angle will be measured in degrees using the Xsens MVN Awinda system during a visually cued drop vertical jump. Participants will perform the task when a predetermined target color appears on the BlazePod system and withhold movement for other colors. Five successful trials will be recorded. Peak knee flexion will be identified during the landing deceleration phase, from initial ground contact to maximum dominant-knee flexion.