> ## 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.

# Loading Phase Lack of Trunk Coil

> Binary indicator if trunk coil is below the acceptable threshold during the loading phase.

## Technical Details

* **Variable Type:** Movement Flag
* **Data Type:** Integer
* **Units:** N/A
* **Column Name:** `loading_phase_lack_trunk_coil`
* **Optimal Direction:** Lower is better
* **Unknown Value:** -1
* **Measurement:** [Trunk Coil](/biomechanics/activities/tennis/metrics/trunk-coil)
* **Threshold:** Trunk coil less than 110°

## Description

Loading phase lack of trunk coil is a binary indicator that flags when the trunk does not rotate away from the serve direction by at least 110° during the loading phase, which limits the amount of rotational energy stored before the serve.

## Use Cases

* Rotational loading assessment
* Power generation evaluation