> ## Documentation Index
> Fetch the complete documentation index at: https://docs.uplift.ai/llms.txt
> Use this file to discover all available pages before exploring further.

# Y-Balance Lower Quarter

> Biomechanical analysis of Y-Balance lower quarter test, including reach distance and stability measurements.

## 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.

## Example Videos

### Left

<Frame>
  <video controls src="https://uplift-docs-assets.s3.amazonaws.com/stability/stability-y_balance_lower_quarter-left_combined.mp4" />
</Frame>

### Right

<Frame>
  <video controls src="https://uplift-docs-assets.s3.amazonaws.com/stability/stability-y_balance_lower_quarter-right_combined.mp4" />
</Frame>

## 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?