Guide
Form check: what a coach watches on the six movements that matter.
Nearly every strength program is built from six patterns: squat, push-up, lunge, hinge, plank and overhead press. Each one has two or three ways it goes wrong, and a coach watches for exactly those. This guide names them, in the words the coach in Loopform AI uses out loud, so you can check yourself or know what you are being told.
What a form check is, and isn't
A form check is not a judgement of how you look. It is three or four questions asked of every rep: did you go through the full range, did the joints track the way they should, did your trunk hold its shape, and did you finish the rep. A good coach answers those questions from one angle, usually the side, and says one thing at a time. That is what this guide does, movement by movement.
Film it the same way a coach would look at it: whole body in frame, phone propped up at the right height, facing or side-on depending on the movement. The filming guide has the five-second setup.
The six movements
Squat
Depth, knees tracking over the toes, chest staying up. Watched from the front, so both knees are visible.
Push-up
Chest low enough, body in one straight line, locked out at the top. Watched from the side, phone on the floor.
Lunge
Front knee bent to about ninety degrees, trunk tall, even work on both legs. Watched from the side with room to step.
Hinge and deadlift
Hips travelling back, back holding its line, knees soft not folding, standing fully tall at the top. Watched from the side at hip height.
Plank
Hips level with the shoulders, not sagging and not piked, for the whole hold. Watched from the side, phone on the floor.
Overhead press
Elbows locked overhead, no leaning back, no leg drive on a strict press. Watched from the side at chest height.
How a phone camera checks form
Pose tracking finds your joints in each frame of video, on the phone, and turns them into angles and lines: the angle at the knee, the angle at the elbow, how far the hip sits from the straight line between shoulder and ankle, how far the trunk leans from upright. A rep is a trip from standing (or the top of a plank) down past a threshold and back up. Depth is the smallest angle the rep reached. A fault is a line or angle that went past its tolerance for long enough to matter, not a single noisy frame.
That is also why the camera angle matters so much. Knees caving in are only visible from the front; depth, back angle and body line are only visible from the side. Loopform AI asks for the right one before each movement and tells you, out loud, when you are in frame.
For the full story of how a rep is counted, what is thrown away as noise, and the list of things that make a camera miss, read Can an app count my reps? For how the other camera apps compare, see AI form-check apps in 2026.
What it says when it sees something
One cue per rep, in plain words, the way a coach standing next to you would: "Little deeper on the next one." "Knees out, push them over your toes." "Hips are sagging, squeeze your glutes." If the rep was clean it counts it and says so. The movement pages list every cue the coach has for each fault.
Rep counting and form cues are free, with or without a subscription. Video never leaves your phone unless you share a clip. Android arrives in January.