> ## 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 Shoulder Hip Separation

> Maximum difference in rotation of the shoulders and hips (separation angle) during the loading phase.

<img src="https://mintcdn.com/upliftlabs/Ku7T6jLWrJyoK7uq/biomechanics/activities/tennis/images/hip-shoulder-separation.png?fit=max&auto=format&n=Ku7T6jLWrJyoK7uq&q=85&s=35a5423171acfdb9babf91f7de24114d" alt="Hip shoulder separation during loading" width="500" height="500" data-path="biomechanics/activities/tennis/images/hip-shoulder-separation.png" />

## Technical Details

* **Variable Type:** Discrete Metric
* **Data Type:** Float
* **Units:** degrees (°)
* **Column Name:** `loading_phase_shoulder_hip_separation`
* **Measurement:** Maximum separation angle between shoulder and hip rotation in the transverse plane during the loading phase ([Ball Release](/biomechanics/activities/tennis/events/ball-release) to [Low Arm](/biomechanics/activities/tennis/events/low-arm))

## Description

Shoulder hip separation during loading is the maximum angular (twist) difference between the torso and pelvis (transverse plane) during the loading phase.
It indicates how much the upper body is "coiled" relative to the lower body before the serve.

Also known as X Factor.

## Use Cases

* Coiling and kinetic chain assessment
* Comparison with [Contact Phase X Factor](/biomechanics/activities/tennis/metrics/contact-phase-x-factor) at apex
* Technique and power potential