> ## 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.

# Seat Off

> The instant the pelvis leaves the seated position at the start of each sit-to-stand rise.

## Technical Details

* **Variable Type:** Event
* **Data Type:** Integer
* **Units:** Frame number
* **Column Name:** `seat_off_frame`
* **Required for QA:** True
* **Recurring:** One frame per repetition
* **Measurement:** Last frame before the rise at which the pelvis is within 10% of the repetition's rise amplitude above the low point the rise starts from

## Description

Seat Off marks the moment the person leaves the chair and begins to stand.
It is detected from the vertical trajectory of the hip center (pelvis keypoint), smoothed with a 0.1-second moving average.
For each repetition, Uplift finds the low point that the rise starts from and takes the last frame within 10% of the rise amplitude above that low point.
Because the threshold is referenced to each repetition's own low point rather than a single seated height for the whole capture, touch-and-go repetitions that bottom out slightly above the chair are still detected.

Seat Off starts the [Rise](https://docs.uplift.ai/biomechanics/activities/stability/sit_to_stand#phases) phase.
Per-repetition metrics are stored at each repetition's Seat Off frame.

## Use Cases

* Start of each repetition and of the [Total Time](https://docs.uplift.ai/biomechanics/activities/stability/sit_to_stand/metrics/total-time)
* [Rise Time](https://docs.uplift.ai/biomechanics/activities/stability/sit_to_stand/metrics/rise-time) and [Repetition Time](https://docs.uplift.ai/biomechanics/activities/stability/sit_to_stand/metrics/repetition-time)
* Start of the window for [Peak Rise Velocity](https://docs.uplift.ai/biomechanics/activities/stability/sit_to_stand/metrics/peak-rise-velocity) and [Peak Trunk Flexion](https://docs.uplift.ai/biomechanics/activities/stability/sit_to_stand/metrics/peak-trunk-flexion)


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