Iron Chapter

Premium AI Fitness Coach · TestFlight Now Open

Every set. Every bite. AI writes the story.

Multi-stage AI coaching with shipped memory, science citations, and an accountability loop.

Other apps run a single LLM and hope. Iron Chapter runs deterministic rules first, an LLM that reviews them, and a critic that checks the low-confidence calls. Science questions are answered from a retrieved corpus of peer-reviewed research — with citations pulled from the papers themselves, so they can't be invented. And every memory it keeps about you is yours to inspect, edit, or delete.

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71,060 research citations Source-labelled food logging Platform-aware wearable connections Privacy-first memory

Pulse · Iron Chapter Coach online · reasoning live

Should I cut carbs tonight?

Keep carbs in. Your last four evening sessions had progressive PRs on full-carb days — pulling them now would compound the poor-sleep week you're already in.

3 studies cited Why I'm saying this ↓

Remembering: prefers evening training

Show, don't tell

Most fitness apps show you a number. We show you our work.

Tap any coach response and Iron Chapter opens it up. The deterministic rule it started from, the reasoning the LLM applied, the safety checks it ran, the research it pulled, the memories about you it used. Nothing is hidden. Nothing is hallucinated quietly. If it's wrong, you can see where it went wrong — and tell it so.

Should I cut carbs tonight?

Keep carbs in. Your last four evening sessions had progressive PRs on full-carb days — pulling them now would compound the poor-sleep week you're already in.

3 studies cited

Why I'm saying this

Rule

Evening training → moderate carbs help recovery

Reasoning

Your last 4 sessions logged progressive PRs on full-carb days

Memory

You mentioned poor sleep last week → no late stimulants

Citations

Burke 2018 · Helms 2014 · Aragon 2017 — tap to read on PubMed

Evidence grade

High — each source carries its own grade

That's a real coach behavior, shipped today. Not a roadmap promise.

Architecture

Four layers, and none of them is "ask the model and hope."

This is what most "AI fitness apps" don't have.

Rules first.

Before any AI runs, deterministic rules check the basics — deficit, last session volume, sleep, safety flags. Rules are auditable, predictable, and never hallucinate.

Then an LLM reviews.

A language model reads the rule output as a prior, not a command. It can agree, suppress, modify, or ask one diagnostic question — but only with reasoning it can show you.

A critic checks the uncertain calls.

When the reviewer's confidence falls below threshold, a second pass critiques the first — looking for safety blind spots, unsupported claims, missing context. It can override the first model.

Safety sits above all of it.

Thirteen categories — emergency symptoms, disordered eating, pregnancy, medications, PEDs, minors — short-circuit before any model runs and return a written response, not a generated one. The model never gets the chance to improvise.

"Every other AI fitness app runs one model and hopes."

Product surface

Built like a real fitness operating system.

Today — your daily command center

Open the app to one screen that already knows your day: your muscle-coverage map across the last two weeks, calories and macros against target, steps, sleep and water, and — if you've connected a wearable — an HRV and resting-heart-rate readout. Below it, the three things actually worth doing today. Streak-freeze credits build up quietly so one missed day doesn't undo a month.

AI Coach

Natural-language chat, with an option to have answers read back aloud. Full context: profile, today's logs, training history, the corrections you've made, and — with a wearable connected — your sleep, HRV, recovery and strain. Asks clarifying questions instead of guessing, and routes to specialist lanes (hypertrophy, supplements, injury-aware, wellness) when your question needs depth. It adapts to your onboarding intent — workouts-only, just meal ideas, or a gentler relationship with food — and anchors to the personal reason you gave for starting, so your why resurfaces when motivation flags.

Food, with trust labels

Log in plain language — "two rotis with rajma and a small bowl of curd" — and every item comes back labelled with where its numbers came from: verified, database, external provider, or AI-estimated, with low-trust items held until you confirm. Override a value and the original source stays visible next to yours. Resolution runs against USDA FoodData Central, Open Food Facts, Edamam and FatSecret, plus our own verified and community-contributed entries. Meal plans respect your budget, cooking skill, and disliked foods. Logs save offline and sync when you're back online — you never lose an entry.

Periodized workouts

100 pre-built programs running 4 to 12 weeks, with periodization and deload weeks designed in — every set carrying a target RPE, not just sets and reps. 714 reviewed exercises, each with setup steps, form checkpoints, common mistakes and goal-specific dosing; 475 have male and female demonstration images. PR tracking, supersets, RPE and reps-in-reserve, equipment-aware swaps, and an iOS Live Activity rest timer on your lock screen and Dynamic Island. A built-in plate calculator, form guide overlays, and warm-up ramps calculated from your working weight. Voice logging mid-set — say "100 for 8" and the app writes it. One tap can reduce the load, extend rest, report discomfort, or open a mid-workout Coach Call grounded in the set you just finished. Miss a week and the plan shifts forward — you don't fall behind.

Progress that explains itself

Muscle balance, weekly volume, consistency rings, recovery trends, macro adherence, net energy. Weekly sleep and training audits grade your week and surface up to three ranked recommendations. Earn achievement badges as you go, and get a yearly "Wrapped" recap of everything you lifted. Every card explains the why — not just the number.

Auditable

Citations you can click, from papers we actually retrieved.

Most fitness apps say they're "science-backed" and leave it there. When you ask Iron Chapter a science question, it searches a corpus of 71,060 peer-reviewed references across 5,827 journals and answers from what it finds. The citations you see are built from the retrieved records themselves — not written by the model — so they can't be invented. A separate check re-reads the answer against those records and flags anything it can't ground.

Peer-reviewed references

71,060

Across 5,827 journals — click any citation to read

Traceable to PubMed

99.97%

71,042 carry a PubMed ID · 68,809 a DOI

Graded high-evidence

17,261

Every source carries its own evidence grade

Your in-app research feed adds new studies as they're indexed and graded. Tap "Ask Coach about this paper" on any of them to see exactly what it changes for your training.

"If we cite a study, you can click it. If we make a claim, we can defend it."

Trust & Evidence

The safety layer runs before the model does.

Most of what keeps a health chatbot safe is what it never gets to say. Iron Chapter checks every message against thirteen risk categories first — and where one matches, the answer is written, not generated.

Ask a general-purpose model for dosing on a potentially lethal weight-loss chemical "for research" and it may well answer. Iron Chapter's guardrail intercepts that class of request before any model is called, and responds with a written refusal that carries no numbers at all.

Covered categories include emergency symptoms, disordered-eating language, prolonged fasting, extreme calorie targets, unsafe rate-of-loss requests, pregnancy, medications, performance-enhancing drugs, injury escalation, and users under 18. A separate firewall blocks prompt-injection and off-domain requests. Not a medical device or diagnostic tool.

What we control

🔒 Data encrypted (in transit & at rest) 🙅 We never sell your data 🔒 Privacy policy ✉️ Privacy request support ♿ Screen-reader labelled · in-app text scaling 🔑 No AI keys in the app · authenticated server proxy 👩‍⚕️ Expert-reviewed content soon 📱 Privacy disclosed on App Store & Google Play

Earned proof

⭐ App Store rating soon 🏆 Product Hunt #1 soon 💬 Trustpilot soon ❤️ Works with Apple Health 🔬 How we handle safety — read our approach

How we keep the coach safe and accurate

Three things, none of which depend on trusting a model. Risky requests are intercepted before generation and answered from written templates. Science answers are grounded in retrieved papers, and a second pass flags any citation the answer can't support. And the coach is told, in its own instructions, not to claim an exercise is uniquely proven when the evidence behind it is general programming guidance — a line we hold on this page too. We're building an internal benchmark to put numbers on this; until it's reproducible and reviewed by a credentialed dietitian, we're not publishing a score. We'd rather show you the mechanism than a figure you can't check.

Iron Chapter is an evidence-based wellness coach, not a licensed medical provider. It does not diagnose, treat, or replace your doctor, dietitian, or emergency services. For medical, medication, pregnancy, or urgent concerns, consult a qualified professional.

Memory, your way

Iron Chapter remembers you. You decide what it keeps.

Real coaches remember you. They know you train at 9pm, that paneer doesn't sit well, that you're working around a bad shoulder. Iron Chapter builds the same memory — but with rules most apps refuse to follow.

✓Every memory shows you why Iron Chapter believes it, and where it came from. Provenance is required, not optional.
✓Nothing learned from a conversation reaches the coach until you approve it. Suggestions sit in a review queue you control.
✓No AI reads your chats to build memory. Extraction is deterministic pattern-matching, and it skips anything about other people, any contact details, and any language suggesting disordered eating.
✓Health-related memories — allergies, injuries, conditions — can be excluded from coaching in one switch. You can edit any memory, pause memory entirely, or delete it for good.
✓Delete is a real delete, not a hidden flag. Delete your account and your memory goes with it.

Straight about the defaults: memory is on when you start, and you turn it off rather than on. The switches are global — memory, chat suggestions, coaching use, and health-sensitive content — not one per category.

Wearable-aware

Your coach can see what your watch sees.

Wearable connections depend on your platform, plan and the connections enabled in the app. Fitbit connection is deferred for the Android launch; manual logging and saved history remain available. Where supported, synced activity and recovery data can inform coaching.

Apple Health

Health Connect

Fitbit · Android deferred

Whoop

Garmin · soon

Oura · soon

Strava · soon

Pulse · using wearable context "Your HRV dropped 18% overnight — I'd suggest a Zone 2 cardio swap today instead of legs."

Wearable data shapes what the coach says. It does not silently rewrite your programme — load, volume and targets stay yours to change.

Free to start

Start free. Choose the support you need.

Free covers core tracking, recent history and basic Progress. Pro adds advanced app features and supported Connected AI connections. AI Pro adds hosted coaching and AI meal and workout tools. Current prices and availability are shown inside the app.

Free, forever

What you get without paying.

A real product, not a trial. No time limit, no card on file.

Core food and exercise tracking
Recent history
Basic Progress

AI Pro includes 100 Coach messages each day. Pro lifetime covers Pro features; hosted AI coaching is a separate upgrade. Existing purchased access is preserved.

Free, Pro and AI Pro · Optional upgrades in-app · No ads · No data sales.

Try Iron Chapter free in TestFlight →

FAQ

Honest answers to the questions we get most.

How is this different from Cal AI / MyFitnessPal / MacroFactor?

Cal AI is a photo-logger; we're a reasoning coach. MyFitnessPal is a database; we're a thinking partner. MacroFactor adapts macros well but doesn't explain why or remember your context the way we do. Iron Chapter is built around the question those apps don't answer: why should you do this, and what worked for you last time?

Is the science-backed claim real, or marketing?

Real, and narrower than most apps mean by it. Ask a science question and the coach retrieves from a corpus of 71,060 peer-reviewed references — 99.97% with a PubMed ID — and cites what it actually pulled, with links you can open. A second pass flags any citation the answer can't support. What we don't claim: that every single message carries a citation (retrieval runs on science questions, not small talk), or that we've published a benchmark score. We're building one; until it's reproducible and a credentialed dietitian has reviewed the transcripts, we'd rather show you the mechanism than a number you can't check.

What about my data and privacy?

Memory is on by default and you turn it off — we'd rather say that plainly than call it opt-in. What you get in exchange: every memory is inspectable with its source shown, editable, and deletable for good (a real delete, not a hidden flag). Anything the app picks up from a conversation waits in a review queue until you approve it, and no AI reads your chats to build it — extraction is deterministic pattern-matching that skips other people, contact details, and disordered-eating language. Health-related memories can be excluded from coaching with one switch. Deleting your account removes your profile, logs, chats and memory; a small amount of billing and support telemetry is retained with your identity stripped out. We do not sell data. We do not run ads.

Does it work for vegetarian, vegan, Indian, Mediterranean, or keto diets?

Yes. Food resolution runs against USDA FoodData Central, Open Food Facts, Edamam and FatSecret, plus our own verified database and community-contributed entries — with Indian staples referenced against IFCT 2017 values. Vegetarian, vegan, eggetarian, pescatarian, Jain, sattvic, halal, gluten-free and lactose-free are enforced as hard filters on generated meal plans. Keto, paleo and Mediterranean are honoured in planning but not filtered afterwards, so check those plans. Niche regional cuisines: file requests in-app and we add them.

How much does it cost?

Free includes core tracking, recent history and basic Progress. Pro adds advanced app features and supported Connected AI connections. AI Pro adds hosted AI coaching, including 100 Coach messages each day, and AI meal and workout tools. Pro lifetime does not include the separate AI Pro upgrade. The app shows current regional prices, eligible offers and billing terms before purchase; existing purchased access is preserved.

When does it launch?

Public App Store and Play Store launch this quarter. TestFlight is open now for founding members.

Can I use it without a wearable?

Yes — wearables enrich the coach's context, but everything works on manual logging too.

Metric or imperial?

Both for logging — switch between kg and lbs anytime, and the active workout screen follows. Being straight with you: several progress charts still render in kg only. That's on the fix list, not a design choice.

Can I use Iron Chapter without tracking food?

Yes — and it's not just a setting we let you turn off. Pick a workouts-only path (or "just meal ideas," or "gentler relationship with food") during onboarding and the app reshapes: nutrition surfaces go quiet, Today focuses on movement and recovery, and the coach changes how it talks to you. You can switch modes any time in Profile.

Are you VC-backed?

Founder-funded today; opening a seed round soon. If you're an investor, reach out.

From the founder

Why we built this.

I've used every fitness app on the market. Most of them treat you like a row in a spreadsheet. The good ones track macros well. The popular ones make logging fun. None of them coach.

A coach knows what you ate, what you trained, what worked last time, what your sleep did to your hunger last week. A coach can tell you why the recommendation is what it is — and disagree with itself when the evidence changes. That's what Iron Chapter is built to be. Not a tracker that bolted on a chat window, but a coach with a multi-layer brain, real memory, and the honesty to show its work.

If that resonates, join the TestFlight. Tell us what we get wrong — and there will be things. We've deliberately kept a benchmark score off this page until it's reproducible and reviewed by someone with credentials we don't have. Grading yourself isn't evidence. Your feedback is closer to it.

— Rishi, founder