Know exactly how fast you’re building muscle.
Your food, training, and recovery become one live number — your Build Pace — so you finally know whether today is building muscle, or just passing time.
You train hard. But is it working?
You lift, you eat the chicken and rice, you tell yourself it’s paying off. But “probably” isn’t proof. Most apps count what you ate and stop there — they never tell you whether today actually moved you closer to muscle.
One number tells you if today counted.
Build Pace turns your whole day into a single live multiplier. At 1.0× you’re holding steady. Above it, you’re building — and the higher it climbs, the faster muscle is going on. No more guessing whether you did enough.
No calorie deficits. No red numbers. No “you failed today.” If your goal is to subtract weight, use something else. If it’s to add muscle, this is your app.
See what moves your pace.
Every habit carries a cost and a payoff. Stack the things that build muscle and watch your Build Pace respond — so you know which choices actually matter, not just in theory.
Tap a habit to see how your day adds up.
Not just a score. The next move.
PRTN reads your day, your training, and your recovery, then hands you the single change that matters most right now — your highest-impact lever. Do that one thing, and watch tomorrow’s pace climb.
You’re 32g short on protein and you trained legs hard. Get a protein-rich dinner in tonight and you’ll cross from Holding into Building.
Log your whole day in seconds.
Snap a photo, scan a barcode, or just say what you ate. PRTN reads protein, calories, carbs, and fat in one pass — every meal, not only the high-protein ones. The less it feels like tracking, the more your pace reflects your real day.
- Photo scan — point, shoot, done
- Describe it in plain words
- Barcode in a single tap
- Apple Health syncs the rest
Three steps. Two minutes.
Log your day
Every meal, the easy way — photo, barcode, or a quick description. Known amounts take two seconds.
Recovery flows in
Workouts, sleep, and HRV sync from Apple Health automatically. Nothing extra to track.
See your pace — and your move
One live number shows how fast you’re building, plus today’s single highest-impact lever.
Everything pulling toward muscle.
Catch the anabolic window
Finish a workout and your protein countdown starts — so you fuel the window right when it counts.
Recovery, counted for you
Sleep, HRV, and workouts sync from Apple Health and lift your pace automatically — nothing extra to log.
See a year ahead
A 12-month muscle projection from day one — calibrated to sports science, not hype.
Supplements that earn their place
An evidence-based stack tuned to your body, training, and sleep. No fairy dust.
Built on the research, not vibes.
Your Build Pace and 12-month projection are calibrated to peer-reviewed sports science — protein dose-response, training volume, and the role of sleep in muscle protein synthesis.
Build Pace is an orientation value to guide your training — not a medical prediction.
- Morton et al., 2018 — protein dose-response meta-analysis (49 studies)
- Schoenfeld — training volume & frequency for hypertrophy
- Lamon et al. — sleep and muscle protein synthesis
- Damas 2015 · Witard 2014 — MPS time-course
See the muscle you’ll actually build.
From your inputs, PRTN projects realistic lean-mass gain over a year — the honest curve, plateau and all. The truth is more persuasive than the pitch.
Real training, finally visible.
+4.2 kg lean mass in 14 weeks.
First time my training actually showed. PRTN connected the dots between lifting, eating, and recovering. The mirror finally caught up to the work.
Down 8 kg of fat. Up 4 kg of muscle.
I came to lose weight. I left with a body I actually built. Recomp clicked once I tracked what builds muscle, not just what burns calories.
Stronger at 42 than I was at 32.
Held my muscle through a brutal year of work. The numbers on the bar still go up. PRTN is the only app I open every morning.
Start building — and know it’s working.
Free to download on iOS. Get your personalized plan in two minutes.
Before you start.
Is this a weight-loss app?
No — the opposite. PRTN is built to add muscle, not subtract weight. No calorie-deficit framing, no red numbers, ever.
Do I have to log every meal?
Log what you eat across the day — every meal counts toward your Build Pace. AI scanning makes it a two-second habit, not a chore.
Is it for women too?
Yes. PRTN is for anyone who trains to build or hold muscle. Your plan is calibrated to your body, not a stereotype.
Is the science real?
Your Build Pace and projection are calibrated to peer-reviewed research (Morton 2018, Schoenfeld, Lamon). It’s an orientation value, not a medical claim.
What do I need?
An iPhone. Apple Health unlocks automatic recovery and training input, but you can log everything manually too.
Is my data private?
Your health data stays yours. No ads, no data selling — ever.