How to Film Your Cycling Position for a Reliable Analysis
BikeFit AI measures your joint angles on the video, frame by frame, at every pedal stroke. How accurate those measurements are depends directly on the video. This page explains why to film a certain way, how to do it, and the two screens of the app that help you: the camera check before you film, and the video quality in your result.
Why the way you film matters
The analysis locates your joints on every frame: shoulder, hip, knee, ankle. From them it derives the angles of the knee, hip, torso, shoulder and elbow, then follows them over several pedal strokes. Three consequences:
- From the side, for the position analysis. This is the view professional bike fitters use to measure these angles: it shows how the knee and hip flex, and how the torso leans. A front or rear view shows something else, such as the path of the knees; it does not replace the side view for these angles.
- While pedalling. A position is judged in motion, over complete and regular pedal strokes, not on a photo.
- Forwards. When you pedal backwards, the knee and ankle angles are reversed: the analysis does not accept them.
How to film: the rules the analysis checks
Before you film, the app always tells you which view it expects. For the position analysis, it is the side view:
- Put the bike on an indoor trainer. It keeps the bike still while you pedal.
- Film from the side, left or right. Place the phone to the side, perpendicular to the bike. Avoid oblique, three-quarter angles.
- Stay entirely in the frame, feet and pedals included. Move the phone back until the whole cyclist is visible.
- Pedal forwards, at a normal and steady cadence, as on the road, without stopping during the recording.
- Give it light. Avoid backlighting and very dark backgrounds.
- Put the phone on a stable surface, in portrait or landscape. In landscape, unlock screen rotation.
- Charge the phone, or plug it in. On low battery, power saving slows it down and makes it drop frames.
With the in-app camera, recording stops by itself once the required duration has been filmed. A video taken from your gallery follows exactly the same rules.
Before you film: the camera check
When you film with the in-app camera, the phone measures its conditions on the preview for about two seconds, before you start recording. It then shows what it found, line by line, and estimates the result.
What each line means:
- Device: the phone and its system version.
- Frames / s: the number of frames per second the camera really delivers. With too few frames, knee angles are less accurate and the overlay, that is the skeleton drawn on your video, is jerky.
- Light: the exposure time, that is how long each frame takes in light. When light is short, the camera lengthens the exposure, slows down and drops frames.
- Battery: the charge level, and whether the phone is plugged in.
- Position: portrait or landscape. The only case flagged is a phone held in landscape with the screen locked in portrait, because the video would come out rotated.
- Resolution: the size of the image the camera films.
A green dot marks a favourable value, orange a borderline value, red a value that degrades the analysis; a grey dot is a simple observation (the device, the position). The estimate says in one sentence whether the analysis looks reliable, or what may degrade it, with the matching advice. The check never blocks you: you can always film.
A value the phone does not provide has no line. This is the case for light and battery on iPhone, whose browsers do not give this information.
In your result: the video quality
After the analysis, the "Video quality" block sits just above "Optimizing your position", in the result as in your history. It is folded: its header shows the share of the video used, with a level (Excellent, Good, Average or Low). Opened, it shows the video as the analysis received and read it.
Video quality
95% · Excellent
The reliability of the measurement depends on it.
| Analysed video | |
|---|---|
| Source | Gallery |
| Frames / s | 60 |
| Analysed resolution | 1280 × 720 |
| Analysed duration | 28.5 s |
| Filmed side | Right |
- Source: the phone gallery or the in-app camera.
- Frames / s: the frames per second of the video received.
- Analysed resolution: the size of the image the analysis actually read, after any downscaling of a larger video.
- Analysed duration and filmed side.
If part of the frames could not be read clearly, the level turns orange and a sentence says so: the measurement is then less reliable. With the in-app camera, the block adds the conditions measured by the camera check. With a calibration tag, it adds the parallax and the tag distance. A line only appears if its value was measured.
This block also helps you understand the gap between two analyses: a video received with fewer frames per second, or with a smaller share used, gives a less accurate measurement.
If the analysis rejects the video
A video that does not allow a reliable measurement is rejected, rather than producing an approximate result. The app tells you why: no cyclist detected, profile not detected, or insufficient pedalling. It also lists the points to check. Your analysis credit is not consumed: go back over the rules above and film again.
For an even more precise measurement: the calibration tag
With the Pro plan, a printed calibration tag attached to the bike measures the parallax, that is the angle between the camera axis and the bike. A camera slightly at an angle distorts the angles: the tag lets you correct it before you film.