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Can AI watch your workout video and get your form right? We tested it
AI feedback that sounds confident but is wrong is worse than no feedback. If an app tells you your back rounded when it didn't, you'll start fixing a problem you don't have. If it tells you a rep was perfect when your hips shot up first, you'll keep doing it until it hurts.
So before we launched Rep Review, we spent weeks testing how accurate AI form feedback actually is, with real coaches judging the results. Here's what we found, and why every Rep Review is now written by one AI and checked by a second.
Can AI analyse videos?
Yes. The latest AI models can watch a video, or a sequence of still frames taken from it, and describe what's happening: who's in the shot, how they're moving and what changes from one moment to the next. That's what makes an AI personal trainer that checks your technique possible.
But “can describe a video” isn't the same as “can coach you”. Judging exercise form means spotting small things at exactly the right moment: hips rising a fraction before the chest, arms bending too early, a heel lifting at the bottom of a squat. That's where AI video analysis gets harder, and where we found the biggest differences between models.
We tested several AI models on real coach footage
We filmed 17 clips of an experienced CrossFit coach, covering squats, deadlifts, push-ups, lunges, kettlebell swings and bar muscle-ups. Then we ran every clip through several of the leading AI models and compared what they said.
On most clips they agreed on the main coaching point. But where they disagreed, the pattern was clear: different models get things wrong in different ways.
- One model over-coachedIt found something to fix in almost every rep, used coaching jargon a beginner wouldn't follow, and once criticised the athlete's back position before the lift had even started.
- Another under-coachedIt was clearer and easier to read, but it called some reps “largely fine” when there was something worth fixing, and it occasionally described things that weren't there. On one deadlift clip it counted the athlete standing up without the bar as a rep.
- A third was ruled out completelyOn a bar muscle-up it got the swing positions the wrong way round, and it missed that a lunge had been labelled as the wrong type of lunge.
None of these models is bad. They're all impressive. But “impressive” isn't good enough when someone is going to change how they lift because of what it says.
Then we asked coaches to judge, blind
We took the clips where the AI models disagreed and showed both reviews to coaches side by side, exactly as they'd appear in the app. The reviews were labelled only A and B, in a random order, so the coaches didn't know which model wrote which. For each clip they had to pick the better review and explain why.
The result was close, and the reasons mattered more than the score:
- Coaches preferred the clearer, plainer review more often. Jargon puts people off, even when it's correct.
- But the more thorough model caught a genuine, common muscle-up fault (bending the arms too early instead of pressing the bar down) that the clearer one missed completely.
In other words, neither model on its own gave the best review. One was clearer, the other was more thorough.
So we use one AI to write and a second to check
Rather than pick one, Rep Review uses both. One AI watches your clip and writes the review in plain English. A second AI then goes back over your video, point by point, and checks the review before you see it. It:
- Works out the timeline firstWhen you set up, when the rep actually starts and when it finishes, so it never criticises a position before you've started lifting.
- Checks every claim against the picturesAnything it can't see in your video is corrected or removed.
- Moves each comment to the right momentSo the picture on each card shows exactly what the feedback is about.
- Keeps the plain wordingWherever the first review got it right.
On the hardest clips from our tests, the checker made a major correction more than half the time. It found the real main fault on a squat that the first review had missed, removed a fault that had been invented on a push-up, and removed that “rep” where the athlete was just standing up without the bar.
What this means for your reviews
- Feedback you can act on. Each point is tied to the exact moment in your clip, written in plain English, and checked before you see it.
- The good bits as well as the fixes. You'll see what you're doing well, not just a list of faults.
- Honesty when the video isn't clear. If Riley can't see you or the movement properly, she'll tell you and show you how to film it, rather than guess. An honest “I couldn't see that clearly” beats a confident wrong answer.
How to get the most accurate review
The checker can only check what's in the video. To give it the best chance:
- Film from the side, or at a 45-degree angle for squats and deadlifts.
- Get your whole body, and the bar if you're using one, in frame for the whole rep, from set-up to finish.
- Use good light, and keep other people out of the shot.
- Keep the phone still. A water bottle or a plate makes a fine stand.
Our step-by-step technique guides show how to film each movement, including the deadlift, push-up and bar muscle-up.
What AI form feedback can't do
Rep Review isn't a replacement for a good coach. It's a second pair of eyes for the sessions when your coach isn't watching every rep, or when you're training on your own. If anything hurts, stop and speak to a coach or physio. And if a review gets something wrong, tap thumbs down so we can look at it.
Want a second pair of eyes on your rep?
Rep Review is an AI form coach for iPhone. Film one rep and Riley shows you what's working, the one thing to work on next, and the drills that get you there.
Get Rep Review
Questions
Can AI analyse workout videos?
Yes. Current AI models can watch a video, or a series of frames from it, and describe how you're moving. Judging exercise form accurately is harder, which is why every Rep Review is written by one AI and checked against your video by a second before you see it.
Is AI form check accurate?
It can be, but a single AI model on its own gets things wrong more often than you'd expect. In our tests, a second AI checking the first one's review against the video caught major mistakes on more than half of the hardest clips.
Which AI does Rep Review use?
We use leading third-party AI models, and we'll switch to better ones as they arrive. Whatever models we use, every review goes through the same write-then-check process.
Does a human check my review?
No. Reviews are written and checked by AI so you get them within a couple of minutes. Coaches judged our testing, which shaped how the checks work.
Can an AI personal trainer check my form from a video?
Yes, if the clip is clear. Film from the side or at a 45-degree angle with your whole body in frame, and an AI coach like Rep Review can point out what you're doing well and what to fix, tied to the exact moment in your rep.
Can Rep Review replace my coach?
No. It's built to help between coaching sessions and when you train alone, not to replace a coach who can watch you in person.
Tags: AI video analysis · AI personal trainer · AI fitness coach · Form check · Exercise technique
This article is general information, not medical advice. If something hurts, stop and speak to a qualified professional.