Overview
The sit-to-stand test measures how quickly and powerfully a person can rise from a chair and sit back down over multiple repetitions. It is widely used to assess lower extremity strength, power, and functional mobility, particularly in older adults and rehabilitation settings. The most common variant is the five times sit-to-stand (5xSTS), but Uplift can analyze any number of repetitions from 1 to 25, so other multi-repetition protocols can be captured with the same movement. Each repetition is analyzed in a cyclical pattern: Uplift detects a seat off, stand, and sit for every repetition, reports metrics for each repetition, and summarizes them across the capture.Instructions
Sit on an armless chair with your back upright, feet flat on the floor about hip-width apart, and arms crossed over your chest or stretched out in front. Stand up fully, then sit back down fully, as quickly as possible, for the required number of repetitions. Count reps as you return back to the sitting position. Keep your arms crossed or outstretched throughout the test, and don’t use your arms to assist in any way. Start and finish seated: complete the final sit before the capture ends.Dimensions
Required inputs for processing:- repetitions
Output Variables
Generic Outputs
Every capture includes session metadata, standard joint angle/velocity time series, and 3D keypoint positions common to all movements. See Generic Outputs for the full list.Events
Events are recurring: each event occurs once per repetition, and its column lists one frame per detected repetition.Phases
Per-Repetition Metrics
One value per repetition. Each value is stored at that repetition’s Seat Off frame (or its Stand frame if Seat Off was not detected), and every other frame is-1.
Summary Metrics
Notes
- Events are detected from the vertical trajectory of the hip center (pelvis keypoint).
- Up to 25 repetitions are analyzed per capture. Captures with no detected repetitions or more than 25 fail QA.
- QA also fails if any repetition is missing its Seat Off or Sit, if events are out of order, or if Total Time is implausible for the number of repetitions. Finish the capture seated so the final Sit is detected.
- Repetitions that rise less than 80% of the capture’s largest rise are flagged as invalid. They are still included in the per-repetition output and averages, but are skipped by Rise Time Change and Relative Power Change.
- Per-repetition values that cannot be calculated (for example, because an event was not detected) are
-1. Summary metrics that cannot be calculated are empty (NaN).