> ## 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.

# Trunk Stretch

> Twist range of motion of the trunk during the serve.

## Technical Details

* **Variable Type:** Discrete Metric
* **Data Type:** Float
* **Units:** degrees (°)
* **Column Name:** `trunk_stretch`
* **Measurement:** Total twist (like a tornado) range of motion of the trunk during the serve
  * typically from maximum coil (away from serve direction) to maximum rotation during follow through

## Description

Trunk stretch is the twist range of motion of the trunk through the serve.
It captures how much the trunk rotates in the twist direction from the coiled position ([Trunk Coil](/biomechanics/activities/tennis/metrics/trunk-coil)) through the acceleration phase to contact.
Greater stretch can indicate more potential for energy transfer.

## Use Cases

* Trunk mobility and range of motion
* Kinetic chain and energy transfer
* Comparison with pelvis stretch