> ## 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.

# Reverse Spine Angle

> Binary indicator of a reverse spine angle — the trunk tilts toward the target during the backswing instead of away from it, identified when the mid-shoulder position moves in front of the mid-pelvis position by more than 5 cm.

## Technical Details

* **Variable Type:** Movement Flag
* **Data Type:** Integer
* **Units:** N/A
* **Column Name:** `reverse_spine_angle`
* **Optimal Direction:** Lower is better
* **Unknown Value:** -1
* **Measurement:** Mid-shoulder X position vs. mid-pelvis X position, between P1 Address and P5 Transition
* **Threshold:** Mid-shoulder X position exceeds mid-pelvis X position by more than 5 cm (0.05 m) at any point during the backswing

## Description

Reverse Spine Angle flags a backswing fault where the upper body tilts toward the target instead of away from it, identified when the mid-shoulder position moves ahead of the mid-pelvis position (along the swing direction) by more than 5 cm between Address and Transition.

## Use Cases

* Posture fault detection
* Backswing mechanics coaching
* Injury risk screening