> ## 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 Coil

> Max rotation angle that the trunk turns away from the pitcher. This measures the loading of the trunk during the swing.

## Technical Details

* **Variable Type:** Discrete Metric
* **Data Type:** Float
* **Units:** °
* **Column Name:** `trunk_coil`
* **Aggregation:** mean
* **Precision:** 0
* **Measurement:** Maximum trunk rotation away from pitcher between [max foot raise](/biomechanics/activities/baseball/hitting/events/max-foot-raise.mdx) and [foot contact](/biomechanics/activities/baseball/hitting/events/foot-contact.mdx) events
* **Reference:** 0° = neutrally square to the pitcher, shoulders in line with the pitch
* **Typical Range:** 24 – 41 °
* **Optimal Direction:** Middle — moderate values are optimal

## Description

Trunk coil measures the maximum rotation angle of the trunk away from the pitcher, indicating the loading and preparation of the core for power generation.
Neutrally sqare towards the pitcher (where the shoulders are in line with the pitch) would be 0 deg.

## Normative Ranges

Percentile distributions by competition level from the 2026 Q1 dataset; the optimal range spans the 25th–75th percentiles.

| Population         | Optimal Range (25th–75th) | 10th | 25th | 50th | 75th | 90th |
| ------------------ | ------------------------- | :--: | :--: | :--: | :--: | :--: |
| Youth              | 28 – 45 °                 |  18  |  28  |  35  |  45  |  53  |
| High School        | 24 – 42 °                 |  17  |  24  |  33  |  42  |  49  |
| College            | 26 – 39 °                 |  17  |  26  |  31  |  39  |  45  |
| Professional       | 22 – 35 °                 |  12  |  22  |  27  |  35  |  39  |
| Broad (All Levels) | 24 – 41 °                 |  16  |  24  |  31  |  41  |  48  |

## Use Cases

* Core preparation assessment
* Rotation evaluation

## Interventions

* [Coil Drill](https://www.youtube.com/shorts/XcvnswS7stw)
  * Focus Area: Back Hip Loading
* [Hook'Em Drill](https://youtu.be/IyCE0hey7-I)
  * Focus Area: Back Hip Loading, Limited Separation