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
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!
I come from a remote area where I don’t have access to fancy gyms and qualified PTs. I’ve tried some workout apps before but each and every one of them lacked some personal touch.
I came across Flex AI recently and I was in love with the UX instantly. I’ve been eagerly waiting for the launch of Flex 3.0 which comes with the AI trainer and honestly it’s a game changer; particularly for a country guy like me.
It’s reliable and improving day by day. It deserves all the recognition.
Flex AI: Your AI Personal Trainer
@mustaq_sameer So glad to hear that you're enjoying the app and UI, and that you're making use of the AI features!
Tried it during my workout today and honestly didn’t expect it to be this good. The form checks actually caught stuff I usually miss, and having quick answers on the spot feels super handy. Kinda feels like having a trainer in your pocket. I’m definitely keeping this in my routine.
@sasha_sashova it's almost addictive right? Like I suddenly want to go to the gym even more so I can admire my Flex history when I'm sore at home the next day 😂
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
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!
I’ve always struggled with feeling judged in the gym because I was never sure if I was doing movements correctly. YouTube tutorials helped a bit, but without real feedback I still couldn’t tell what I was doing wrong. Having something that gives instant form cues has been a huge confidence boost. Using this in beta was honestly a game-changer, and I’m excited that more people who deal with the same anxiety can finally try it too.