The problem
Subscription fitness apps are built for the median user. Each one is competent at a slice of the job, but none knows your specific program, your equipment, your schedule, or the fact that your back squat is lagging. YouTube programs are static. They have no memory, no coach, no progression.
The gap between "a coach in your pocket" and what is actually available on the App Store is enormous. Our client, a fitness content creator, wanted to close that gap, starting with themselves.
The brief was direct: build one app that replaces the stack, owns its own data, and runs as a native-feeling tool on the home screen.
What we built
A custom progressive web app. It installs to the home screen on iOS and Android, works offline, and loads in under a second on cellular. One user, one program, one system of record.
1. A program-aware Today screen
The home view shows today's workout, auto-generated from a custom exercise database. Every lift is pre-loaded with a target weight and rep scheme calculated from the last session's performance. No guessing, no manual progression math, no scrolling through spreadsheets mid-set.
Each exercise expands into set-by-set logging with an integrated rest timer and coach tips. Tomorrow and the next five days are visible underneath, collapsible so the user sees only what they need during the session.
Logs queue in local storage if the user is offline, then sync the moment they reconnect. A workout never gets lost because the gym has bad reception.
2. An AI coach grounded in real numbers
The Coach tab is a chat interface powered by Claude. Before every message, the app assembles a context package: the user's full program, today's logged sets, the last seven days of workouts, the latest body composition data, and recent wearable signals if available.
It is not a generic fitness chatbot. It cites the actual numbers. Ask "should I push the back squat today?" and the response references last session's RPE, this week's total volume, and whether sleep recovery is trending up or down.
3. A user-owned backend
The most important architectural choice: there is no backend database to manage. The user's own spreadsheet is the system of record. They already lived in spreadsheets. Rather than migrating them into a new silo, the app meets them where they are.
Sensitive work (model calls and authenticated writes) happens on the server so credentials never touch the device. Everything else runs in the browser, with a clean, modern stack and a typography treatment that feels closer to a good terminal than to a consumer app.
There are no databases to manage, no servers to patch, no monthly bills to watch. The user owns their data, literally, in a spreadsheet they can open in any browser.
The bonus layer: wearables and body composition
Claude can extract patterns from Apple Health and connected smart scales to build coaching around sleep scores, HRV, recovery trends, and body composition targets. Ask the coach to dial back volume on a low-recovery day and it actually looks at last night's sleep score before responding.
Progress charts in the Log tab show volume trends and estimated 1RM curves per lift, so the user can see what is working and what is stalling without opening a separate analytics tool.
The outcome
The app replaced a rotating stack of paid apps and static YouTube programs with a single tool that knows its user cold. Workout sessions run faster because the target numbers are already loaded. Programming decisions are sharper because the coach sees real data. And because the whole thing is a web app backed by the user's own spreadsheet, there is no recurring cost and no risk of a vendor pulling the product.
By the numbers
Why this matters
Off-the-shelf apps are built for no one in particular. This is what software for you looks like: one person, one program, one system of record, one coach that cites the actual numbers.
The same framework rebuilds in days for any client. Bring us your lifts, your equipment, your coach's programming, and your goals. We will deliver a PWA that knows your program cold, logs to a spreadsheet you already own, has a coach chat grounded in your real data, and belongs to you. No vendor lock-in, no ads, no social feed.
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We scope, build, and ship custom tools for operators, creators, and small teams. Tell us what you're using today and we'll map the fastest path to something that actually fits.
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