42K Run.
A single-purpose iOS app for marathon training. Pick your race date and the plan adapts to fit your window — progressive long runs, workout types matched to your goal, and a taper that peaks on race day.
My Role
End-to-end product: marathon domain research, plan generation logic, UX/UI, native iOS & watchOS development.
Timeline
In development throughout 2026. iOS 17+ and watchOS 10+. Native SwiftUI + MVVM, no third-party deps.
Tech Stack
The Challenge
Most running apps try to be everything — 5K plans, HIIT, casual jogging, marathon prep — and end up shallow at every distance. Marathon training has very specific needs: progressive long runs, pace discipline, taper weeks, and a plan that peaks at exactly the right time. Generic apps don't nail any of this, and dedicated coaching apps lock it behind expensive subscriptions.
An app that does one distance, and does it properly. 42.2 km. Nothing else.
The Solution
A dedicated 42.2 km app and nothing else. Pick a race date and a goal level — Finish, Finish Strong, or Personal Best — and the app generates a 16-week plan with progressive long runs, workout types matched to your goal, and a taper calibrated to race day. Start any workout and get a live segment coach with haptic and audio cues. A standalone Apple Watch app mirrors the flow. Live Activity keeps your run visible on the lock screen. Everything syncs to Apple Health.
No subscription. No social feed. No cross-training modules. Just the plan, the run, and the finish line.
The discipline
42K Run is defined by subtraction. Five decisions kept it pointed at one finish line — each one a marker on the way there.
One distance. 42.2 km, nothing else.
Instead of a do-everything app — 5K, HIIT, casual jogging.
Marathon training has specific needs: progressive long runs, pace discipline, a taper that peaks on race day. An app that does one distance nails them; generalists stay shallow at all of them.
The plan bends to your race date
Instead of a fixed, generic plan.
You don’t choose a plan length — you choose a race day. The 16-week structure back-calculates from it, so the build, peak, and taper land exactly when they should.
Three goals, not infinite knobs
Instead of a blank pace-config screen.
Finish, Finish Strong, or Personal Best. Your goal sets your paces — three honest tiers cover real runners without drowning them in settings.
No subscription, no feed, no cross-training
Instead of the coaching-app paywall and social loop.
The plan, the run, the finish line. Everything else is noise between you and race day.
The watch is a peer, not a remote
Instead of a phone-tethered companion.
Runners don’t carry a phone on every run. The Apple Watch app runs the whole workout on its own and syncs back — not a mirror that needs the phone in your pocket.
How It Works
From race date to finish line in three steps
Set
Pick your race date and one of three goal levels — Finish, Finish Strong, or Personal Best. The app generates a 16-week plan that peaks at the right time.
Run
Start any workout from Today and get GPS tracking, a live segment coach for warm-up, main set, and cool-down, plus haptic and audio cues during the run.
Sync
Every run saves to Apple Health. The Apple Watch app mirrors the flow, Live Activity keeps stats on the lock screen, and race prep kicks in 21 days out.
Race day is in 16 weeks, and I want to finish strong — not just survive it.
Plan · 16 weeks
Progressive long runs to race distance
Goal · Finish Strong
Paces matched to your target
Workout · 5 types
Easy, long, tempo, intervals, recovery
Taper · Final 3 weeks
Volume drops, sharpness peaks on race day
Built With
Native iOS and watchOS, deeply integrated with Apple's platform
Core Location
High-precision GPS tracking with 3m distance filter for real-time distance, pace, and elevation.
HealthKit
Read past runs from Apple Health and save every new workout with full metadata.
ActivityKit
Live Activity on the lock screen and Dynamic Island during active workouts.
WatchConnectivity
Two-way sync between iPhone and Apple Watch for seamless handoff.
User Notifications
Workout reminders that respect your schedule without spamming you.
AVFoundation + Haptics
Audio cues and haptic feedback for segment transitions during runs.
The 16-week arc
The real problem isn't tracking a run — it's shaping sixteen weeks so they peak on a date you pick. The whole plan is calculated backward from race day.
Given a race date, the plan works backward: progressive mileage through the build, a peak three to four weeks out, then a taper that sheds volume while keeping sharpness — so race day is the freshest you've been in months.
Screens from 42K Run
From onboarding to finish line — every screen that gets you to race day.
