> ## 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.

# Bottom

> The instant of maximum lunge depth, when the pelvis reaches its lowest point.

## Technical Details

* **Variable Type:** Event
* **Data Type:** Integer
* **Units:** Frame number
* **Column Name:** `lunge_forward_bottom_frame`
* **Required for QA:** True
* **Measurement:** Frame at which the pelvis reaches its peak vertical height (lowest COM position)

## Description

Bottom marks the instant when the pelvis reaches its lowest point during the forward lunge, corresponding to the peak of the vertical pelvis trajectory. This event separates the eccentric (descent) phase from the concentric (ascent/recovery) phase and is the reference frame for bottom-of-lunge metrics such as knee valgus and stance geometry.

## Use Cases

* Eccentric vs. concentric phase definition
* Joint angle metrics at bottom (e.g., knee valgus, hip/knee/ankle flexion)
* Stance length and width measurement