How the camera form check actually works
The short answer
Your phone converts each camera frame into the coordinates of your joints and then throws the frame away. Reps and form errors are worked out from how those points move. The video never leaves your device, and what syncs is a short list of numbers.
“An AI that watches you exercise” is a sentence that makes most people picture a camera streaming their living room to a server somewhere. It is a fair thing to be wary of, and it is worth explaining precisely why that is not what happens here.
The four steps
1Your phone watches, frame by frame
You prop the phone against a wall and stand where it can see all of you. From there it is reading the video stream continuously, not taking photographs. Nothing is captured in the sense of being kept.
2Each frame becomes a skeleton, not a picture
A pose-estimation model finds the major joints — shoulders, elbows, hips, knees, ankles — and reduces the frame to their coordinates. After that step the image is gone and what remains is a list of points in space. This is the part people find surprising: the system never has a picture of you to lose.
3The skeleton becomes reps and errors
Joint angles moving through a known pattern is a rep. Angles going somewhere they should not — knees caving in on a squat, elbows flaring wide on a push-up, hips rising before shoulders on a bridge — is a flagged error, called out while you are still in the set rather than afterwards.
4Only the numbers leave the device
What reaches us is a count of reps, the movements performed, the seconds spent, and the errors flagged. Your session history is built entirely from those. There is no video to request, subpoena or leak, because it was never uploaded in the first place.
Who built the tracking
We did not write the pose-estimation model. The movement tracking in Mira runs on the KinesteX SDK, which is a motion-tracking toolkit other fitness and wellness apps license too, and which handles rep counting, movement classification and the on-device processing described above.
Worth stating plainly: Mira and KinesteX come from the same team, so treat this as a disclosure rather than a recommendation. We are telling you because you should know what is inside a product that points a camera at you, and because “our proprietary AI” would have been the easier and less honest sentence.
What Mira adds on top is the part specific to this situation: sessions sized for a suppressed appetite, a plan that shrinks on a flat day instead of guilt-tripping you, and progress reported in reps and form rather than on a scale.
What a form score is, exactly
It is one number with a boring definition: the share of your scored reps that finished without a flagged error. Forty reps with six flagged errors is 85%. That is the whole calculation, and it is worth knowing because a number with a hidden formula invites you to read meaning into it that is not there.
It is a comparison against your own previous sessions and nothing else. It is not a rating of you, not a fitness level, and not a measure of how hard you worked. Form scores usually climb quickly in the first few weeks, for the unremarkable reason that movements become familiar.
What it cannot see
It sees the errors it has been trained to look for, on the movements it knows. It cannot see the compensation you are making somewhere it is not watching, it cannot feel where your weight is, and it cannot take a history. A good coach standing next to you is better at all three, which is a trade we wrote a whole comparison about.
It also needs conditions: room to be seen head to toe, enough light to resolve your outline, and a phone that is not going to slide down the wall halfway through a set. In a dark room at an angle, it will miss reps.
The movements it starts you on
Nothing exotic, and nothing requiring equipment. These are the ones the first sessions are built from, and the ones the camera reads most reliably.
Sit back towards the chair rather than dropping straight down, and stand up without using your hands.
Elbows travel back at roughly forty-five degrees, not out sideways. The body stays one straight line from heel to head.
Drive through the heels until hips, knees and shoulders make one line. Squeeze at the top, do not arch the lower back.
Pull the elbows past your ribs and let the shoulder blades come together. The pull comes from the back, not the arms.
The fastest way to see whether any of this works for you is to try it. The assessment is free, takes about three minutes, needs no card and does not start a trial. The baseline it gives you is yours to keep whatever you do next.
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