Introducing AI form feedback and AI-powered training coach. Flex AI is the world’s first AI personal trainer. The new update (Flex 3.0) introduces real-time AI Form Feedback and Lex—an AI persona that adapts your workout plan, analyzes your lifts, corrects your form instantly, and answers questions about training, recovery, and nutrition.
Flex AI: Your AI Personal Trainer
@aminniri Seven years of iterating on one problem shows real obsession, in a good way.
What I’m curious about is the breakthrough moment: was there a specific prototype or model that finally made you think, ‘okay, now this is actually possible’?
Because form-tracking has been ‘almost there’ for years, but never truly reliable. Would love to hear what finally clicked for you.
Flex AI: Your AI Personal Trainer
@fernando_scharnick I always believed it was a solvable problem from first principles: if humans can reliably spot form errors and coach someone through a lift, then in theory a machine should be able to learn the same patterns. The issue was that everything out there was either generic pose estimation / body tracking or unstable rule based systems, nobody had built exercise specific models that actually detect form errors rep by rep in real gym footage.
The breakthrough for us wasn’t one single prototype, but the point where our own rep detection and error indication models became as consistent as a good human coach across angles, body types, and edge cases. Once we had enough domain-specific data and models tuned to specific exercises and error types, the reliability finally crossed the threshold where it felt commercially viable.
From there it was years of iteration, new architectures, new datasets, re-labeling edge cases, to make it robust enough for everyday users. Huge credit to the team for grinding through that. Getting something to work in a lab is one thing, getting it to work reliably for real people in real gyms is what took the longest.
@aminniri This is such a fascinating breakdown, especially the part about crossing that “human-coach consistency” threshold.
It’s wild how many teams tried to brute-force this with generic pose models instead of building exercise-specific intelligence.
Huge respect for grinding through all the edge-case labelling… that’s the unglamorous part nobody talks about
ATH.ooo
I've been using Flex for a long time. It's become my favorite way to track my workouts, and I've been hoping it would get an AI trainer and ground-up rethink around AI, so I can't wait to try all these new features!
Flex AI: Your AI Personal Trainer
Having restarted my gym journey, after being stuck with just home workouts and now without a personal trainer, Flex has been my go-to "gym partner" for creating workouts suited to my style and needs. What's now great is how it gives me feedback on my form, during my workouts. Been loving this feature for what it's worth.
No more logging sets manually, no more recording and playing back a video to myself, no more having to remember to progress my weights or reps. It's all taken care of now! Love the new release!
Flex AI: Your AI Personal Trainer
This app is great for people like me who are often in the gym but struggle to maintain a strict routine. I love being able to share my workout results with my friends, and not needing to track on paper.
Having AI generate workouts has been awesome because it suggested some exercises I hadn't tried before, and I'm loving them. Experienced lifters have a lot to learn too!
Flex AI: Your AI Personal Trainer
So proud to be part of the team bringing Flex 3.0 to life after years of work. We poured a lot of love into making the AI interaction feel seamless—can't wait to see you all crush your workouts with it!
I’m personally loving the AI workout generator. It solves the problem of doing the same old exercises and keeps the gym fun and fresh.
Flex AI: Your AI Personal Trainer
The workout generation is a life-saver; ensures I never get bored.
Flex AI: Your AI Personal Trainer
Camocopy
I think calling it "world’s first AI personal trainer" is a bit misleading as there are already quite a few alternatives, also from big providers. Despite this I like the design and straightforward onboarding.
@aminniri @artem_goryaev
Flex AI: Your AI Personal Trainer
@artem_goryaev @jim_engine Totally fair point, “AI personal trainer” has been used loosely by a lot of products. What we mean by world’s first is a full, end-to-end personal training experience that includes real time form feedback, rep by rep error detection, and exercise specific coaching, not just a chat interface or a static plan generator.
When we started 7.5 years ago, nothing like that existed. That’s why we ended up filing a patent for our form feedback system, there was no prior art for models that could detect specific lifting errors, rep by rep, directly from a smartphone camera. That technology is what finally made a complete “AI trainer” experience possible.
Our whole mission is to make the level of guidance you’d get from a great coach accessible to the 99% of people who can’t afford one. So far, the reception has been incredible, and we’re just getting started.
Camocopy
@artem_goryaev @aminniri Thanks for your explanation :)