> ## 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.

# Cocking Phase Lack of External Rotation

> Binary indicator if shoulder external rotation (layback) during the cocking phase is below the acceptable threshold.

## Technical Details

* **Variable Type:** Movement Flag
* **Data Type:** Integer
* **Units:** N/A
* **Column Name:** `cocking_phase_lack_external_rotation`
* **Optimal Direction:** Lower is better
* **Unknown Value:** -1
* **Measurement:** [Cocking Phase Max Shoulder External Rotation](/biomechanics/activities/tennis/metrics/cocking-phase-shoulder-external-rotation)
* **Threshold:** Max shoulder external rotation less than 180°

## Description

Cocking phase lack of external rotation is a binary indicator that flags when the dominant shoulder does not reach at least 180° of external rotation (layback) during the cocking phase, which limits the elastic energy available for the acceleration phase.

## Use Cases

* Layback and shoulder loading assessment
* Injury risk identification
* Mechanics evaluation