Overview
The Y Balance Lower Quarter Test is a standardized, reliable, and widely used clinical assessment tool designed to evaluate an individual’s dynamic single-leg balance and neuromuscular control at their “limits of stability.” It is often employed to identify injury risk, track rehabilitation progress, and determine readiness for return to sport.Instructions
Stand barefoot on one leg (the stance leg) in the center of a specialized platform or marked “Y” shape on the floor. While maintaining balance on the stance leg, use the mobile leg to reach as far as possible in three specific directions:- Anterior (forward): Reaching directly forward from the stance foot.
- Posteromedial (backward and inward): Reaching diagonally backward and across the body.
- Posterolateral (backward and outward): Reaching diagonally backward and away from the body.
Dimensions
Required inputs for processing:- Footedness: The foot maintaining balance [‘left’, ‘right’]
- Direction: The direction of the reach [‘Anterior’, ‘Posteromedial’, ‘Posterolateral’]
Events
| Metric | Description | Column Name |
|---|---|---|
| Bottom | the instant of lowest center of mass during the reach | “ |
Discrete Metrics
| Metric | Units | Description | Column Name |
|---|---|---|---|
| Reach Distance | meters | Maximum reach distance in anterior direction | reach_distance |
| Reach Distance Relative | ratio | Maximum reach distance normalized by leg length | reach_distance_relative |
| Trunk Range of Motion Frontal Plane | degrees | Range of trunk motion in frontal plane during reach | trunk_frontal_plane_range_of_motion |
| Stance Knee Medial Translation | meters | Medial translation of stance knee during reach | stance_knee_medial_translation |
| Stance Hip Range of Motion Flexion | degrees | Range of hip flexion during reach | stance_hip_flexion_range_of_motion |
| Stance Hip Max Flexion | degrees | Maximum hip flexion during reach | stance_hip_max_flexion |
| Stance Knee Range of Motion Flexion | degrees | Range of knee flexion during reach | stance_knee_flexion_range_of_motion |
| Stance Knee Max Flexion | degrees | Maximum knee flexion during reach | stance_knee_max_flexion |
Notes
- Kinematic data typically captured at 30-60 Hz for stability activities
- Test requires footedness specification (‘left’ or ‘right’)
- Leg length is used to normalize reach distance. Relative reach distance of 1.1 = reaching 110% of average leg length.
- Knee medial translation is a valgus displacement measure: how far did the knee move laterally?