> ## 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.

# P4 Top of Swing

> The highest hand position of the backswing and the moment just before the downswing transition begins.

## Technical Details

* **Variable Type:** Event
* **Data Type:** Integer
* **Units:** Frame number
* **Column Name:** `p4_top_of_swing_frame`
* **Required for QA:** False
* **Measurement:** Peak hand height occurring before the X-Factor Zero Crossing event
* **Timing:** Between P3 Mid Backswing and P5 Transition
* **Legacy Name:** Top Backswing

## Description

P4 Top of Swing marks the highest point of the backswing, immediately before the club changes direction into the downswing.
It is found as the frame of peak hand height occurring before the X-Factor Zero Crossing event.
This event is also used as the reference for Upswing Duration, Downswing Duration, and several angle-at-event metrics.

Also exposed under the legacy column name Top Backswing.

## Use Cases

* Backswing completion
* Upswing / Downswing Duration split point
* Kinematic sequence and angle-at-event reference