> ## 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.

# Drive Start

> Start of the drive phase of the softball pitch.

## Technical Details

* **Variable Type:** Event
* **Data Type:** Integer
* **Units:** Frame number
* **Column Name:** `drive_start_frame`
* **Required for QA:** False
* **Measurement:** First frame after high hand where the stepping (lead) ankle passes in front of the pushing (drive) ankle, in the pitch direction

## Description

Drive Start marks the beginning of the drive phase, when the lead leg begins stepping toward the plate and passes the pushing leg. This timing anchors several angular metrics that describe the rotational phase of the delivery.

## Use Cases

* Drive phase identification
* Rotational sequencing analysis