Stack

A strength-training app with a personal AI coach — conceived, designed, built, and shipped by one person.

Role: Solo creator
Platform: iOS, iPhone and iPad
Built with: React Native, Expo, Railway
Status: Live on the App Store

Five ST∆CK App Store screenshots in a row on a dark indigo background: workout plan, AI coach, muscle heatmap, workout log, and weekly volume trends. — App Store screenshots.

Overview

ST∆CK started as a tool for my own training: a fast way to log sets at the gym and actually see progress over time. It grew into a complete consumer product with a personal AI coach, analytics, workout plans, and Apple Health sync.

The design problem was density. Strength training produces a lot of numbers — sets, reps, weights, rest times, muscle groups, months of history. The interface had to make that information quick to enter mid-workout and easy to read at a glance.

My role

Conceived the product and owned it end to end: UX, interface design, development, and App Store release
Designed the visual system, from the interface to the app icon and App Store screenshots
Built with React Native and Expo, a Railway backend, RevenueCat subscriptions, and Resend email
Integrated Apple Health sync and an AI coach grounded in each lifter's own training history

Highlights

On the App Store for iPhone and iPad: Live
Muscle groups in the body heatmap: 22
Person, from concept to launch: 1

Interface

Designed for the gym floor

A dark interface with a restrained palette led by indigo keeps attention on the numbers. The rest timer stays pinned to the top of the screen, each set is a single row of weight and reps, and logging sits at the center of the tab bar.

ST∆CK workout plan screen: a rest timer above a front-and-back body map with trained muscles highlighted and a day-by-day checklist. — Plans fill in a body map as you train.

ST∆CK workout log screen: a pinned rest timer above an exercise card for bench press with three sets of weight and reps. — Log sets without leaving the timer.

AI coach

Coaching grounded in your own data

The aiCoach answers questions about form, rest, and programming using the lifter's actual history — recent sessions, muscle recovery, and personal records — so the advice is specific rather than generic.

ST∆CK aiCoach screen: a chat where the coach answers how long to rest between sets, with guidance for strength, hypertrophy, and endurance. — Ask about form, rest, or programming.

Analytics

Making progress visible

A full-body heatmap shows every muscle trained across 22 groups, filterable by 7, 30, 90, or 365 days. Weekly volume trends per exercise turn months of logged sets into a readable line.

ST∆CK muscles trained screen: a front-view body heatmap in shades of purple and pink with 7, 30, 90, 365-day filters and summary stats. — A heatmap across 22 muscle groups.

ST∆CK weekly volume trend for bench press: a line chart over months above a dated list of weights and reps. — Weekly volume, per exercise.

See the work

View on the App Store

Contact

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Always glad to talk about creative work, live music, and products worth building.

Connect on LinkedIn michaelgilsinan.com