> ## 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.

# Contact Phase Open Pelvis Rotation

> If pelvis rotation at ball contact is above the acceptable threshold.

## Technical Details

* **Variable Type:** Movement Flag
* **Data Type:** Integer
* **Units:** N/A
* **Column Name:** `contact_phase_open_pelvis_rotation`
* **Optimal Direction:** Lower is better
* **Unknown Value:** -1
* **Measurement:** Pelvis rotation at [Apex](/biomechanics/activities/tennis/events/apex)
* **Threshold:** Pelvis rotation greater than -30°

## Description

Contact phase open pelvis rotation is a binary indicator that flags when the pelvis has rotated too far towards the serve direction (past -30°) at the time of ball contact
This indicates the hips are "opening up" too early relative to the arm and ball.

## Use Cases

* Rotational sequencing assessment
* Mechanics evaluation