> ## 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 Trunk Tilt

> Degrees of side-side trunk tilt at apex (ball contact).

<img src="https://mintcdn.com/upliftlabs/Ku7T6jLWrJyoK7uq/biomechanics/activities/tennis/images/trunk-tilt.png?fit=max&auto=format&n=Ku7T6jLWrJyoK7uq&q=85&s=55120786dc6ac631503926bb6ad2cfdb" alt="Trunk tilt at contact" width="500" height="500" data-path="biomechanics/activities/tennis/images/trunk-tilt.png" />

## Technical Details

* **Variable Type:** Discrete Metric
* **Data Type:** Float
* **Units:** degrees (°)
* **Column Name:** `contact_phase_trunk_tilt`
* **Measurement:** Lateral (side-side) trunk tilt at [Apex](/biomechanics/activities/tennis/events/apex) (ball contact)

## Description

Contact phase trunk tilt is the lateral trunk tilt at ball contact.
It reflects posture at the moment of impact and can be compared with [Loading Phase Trunk Tilt](/biomechanics/activities/tennis/metrics/loading-phase-trunk-tilt) to assess trunk motion through the serve.

Negative values indicate leaning to the dominant side, positive values indicate leaning to the non-dominant side.

## Use Cases

* Posture at contact
* Trunk control and consistency
* Comparison with loading-phase trunk tilt