> ## 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.

# Ball Release

> The estimated timing of the ball toss during the serve.

## Technical Details

* **Variable Type:** Event
* **Data Type:** Integer
* **Units:** Frame number
* **Column Name:** `ball_release_event`
* **Required for QA:** False
* **Measurement:** Estimated frame of ball toss release, marked by:
  * when the hand passes above the face, or
  * when the hand reaches its max upwards velocity before apex

## Description

Ball Release marks when the ball is released from the hand during the toss, estimated from hand motion.
It separates the start of the preparation phase from the [Release](/biomechanics/activities/tennis/overhand_serve#phases) and [Loading](/biomechanics/activities/tennis/overhand_serve#phases) phases and is used for timing and [Loading Phase Ball Release Angle](/biomechanics/activities/tennis/metrics/loading-phase-ball-release-angle) metrics.

## Use Cases

* Toss consistency and timing
* Loading phase definition (ball release to low arm)
* Ball release angle assessment