How it works

1. The browser letterboxes each camera frame into 640 by 360 pixels.
2. The browser encodes the frame as JPEG and sends it with the capture time.
3. The server runs MoveNet Lightning through OpenVINO and returns 17 keypoints.
4. Three keypoints make one interior angle, and eight angles come back on every frame.
5. A state machine watches one angle and closes a repetition when the angle returns to the resting value the server measured for you.
6. At the far end of a counted repetition, one fault test compares the peak angle against the range the movement asks for.

What the measurement is worth

Pose model

MoveNet Lightning, FP16, on the processor

What it reads

Eight joint angles a frame, from a side view in the sagittal plane

Published single-camera error

5.5 to 5.8 degrees root mean square, against the 2 to 5 degrees clinicians call desirable

Smallest knee change a clinician calls meaningful

8.48 degrees after stroke

Two clinicians labelling the same recordings

Cohen's kappa 0.63