Your training deserves better software.
FitnessOS logs every set and estimates how recovered each muscle is, so you know what is ready today. No badges. No fake streaks.
15 days of PRO free. No credit card.
Muscle readinesssample readout
Instead of badges, you get answers.
Every screen is built around one question: what should I train today?
Know what is ready.
After every set, FitnessOS estimates how recovered each muscle group is, in percent and hours until ready. It counts sets, reps, how close you went to failure, and which smaller muscles helped.
- Chest, back, legs, shoulders, arms (biceps and triceps separately) and core
- Recovery windows differ by muscle: about 56 h for chest, 66 h for back, 72 h for legs
- A weekly “how did you feel” question tunes it to you
A plan that listens to you.
Pick your split (Push/Pull/Legs, Arnold, Upper/Lower, Bro split, full body) or tap “Suggest for me”. The rules build the program from the exercises you actually have. The AI only explains it.
- You choose days, goal and experience, the plan follows
- Swap any exercise. Nothing changes without your tap
- After 4 to 6 weeks it offers fresh exercises for the same split
It advises. You decide.
Ask “What today?”, “How much rest?”, “Swap an exercise” or “Order my exercises”, and get an answer based on your own numbers. With PRO you can ask anything about your training.
- It never prescribes weights or reps
- If something hurts, the answer is always the same: stop, rest, see a professional
Log a set in one sentence.
Swipe to log, or type or say “lat pulldown 50 x 10”. Ghost Mode shows what you did last time, so beating it is one glance away.
- Swipe, type or voice, in English, Serbian and Spanish
- Exercise library with images and muscle maps
- Works without internet and syncs when you are back
Progress, zero badges.
A calendar of every training day, a volume trend, sets per muscle and a consistency wall. Just your numbers, shown honestly.
Ghost Mode
Your last session, one tap to copy it. Beat yourself, not strangers.
237 exercises
Steps, tips and video for each, in three languages.
Arsenal
Pick the exercises you have, or start from a pack: Full gym, Dumbbells only, No equipment.
Post-workout read
A short analysis after your session, once the app has enough of your history.
Share cards
A clean image of your session or month, ready for your story.
Install, no store
Add it to your home screen from the browser on Android and iPhone.
Log a set. The app does the rest.
Log
Swipe, type or say your set. Weight, reps, done.
Recover
Bio-Engine updates every muscle, with percent and hours to ready.
Decide
“Next up” shows what is ready in your routine. You choose.
See it in use.
Simple. Free to start.
Start with Free forever, or try everything in PRO for 15 days with no card.
Free
- Unlimited logging and history
- Ghost Mode
- Routine generator and all splits
- Next up card and weekly calibration
- 237 exercises, offline
PRO
- Everything in Free
- Bio-Engine recovery per muscle and body map
- FitnessOS Score
- Smart Timer and weekly AI report
- Weekly AI report from Bio-Engine
God Mode
- Everything in PRO
- One payment a year
- Cancel anytime
Prices include tax. Payments by Lemon Squeezy.
Before you start.
Is FitnessOS a personal trainer?
No. It is a tracker. It records, calculates and advises, and the decision is always yours. It does not prescribe weights or reps beyond a starting suggestion.
How is recovery calculated?
From your own logs: sets, reps, load, how close you went to failure, and which muscles helped. It is an estimate, not a medical measurement.
Do I need to download it from an app store?
No. FitnessOS is a web app. Open it in your browser and add it to your home screen on Android or iPhone. It works offline and syncs later.
What happens after the 15 days?
You keep the Free plan forever. PRO features stay locked until you choose to subscribe. No card is needed to start the trial.
Which languages does it support?
English, Serbian and Spanish, across the whole app including all 237 exercises.
What if something hurts?
Stop, rest, and see a doctor or physiotherapist. FitnessOS is a training guide, not medical advice.