> ## 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 Pelvis Rotation

> Pelvis rotation angle relative to its starting orientation at apex (ball contact).

## Technical Details

* **Variable Type:** Discrete Metric
* **Data Type:** Float
* **Units:** degrees (°)
* **Column Name:** `contact_phase_pelvis_rotation`
* **Measurement:** Transverse-plane pelvis rotation at [Apex](/biomechanics/activities/tennis/events/apex) (ball contact)

## Description

Contact phase pelvis rotation measures how far the pelvis has rotated (twisted) by the moment of ball contact, relative to its starting orientation. It reflects how much of the pelvis's rotational range has been used by contact, which relates to the [Contact Phase Open Pelvis Rotation](/biomechanics/activities/tennis/flags/contact-phase-open-pelvis-rotation) movement flag.

## Use Cases

* Pelvis rotation timing
* Kinetic chain sequencing
* Related to Contact Phase Open Pelvis Rotation flag