WorkoutLog app PRD: From concept to launch with AI builders
On this page, you'll find a complete, real-world Product Requirements Document (PRD) for a WorkoutLog app, covering features, metrics, and tech choices. We compare top AI app builders like Lovable, Cursor, and Replit for this use case and offer a starter checklist you can use to turn your gym tracking idea into a shipped product. Get the exact prompt to use with AI builders.
What this is
A WorkoutLog app PRD defines the scope, functionality, and success metrics for a mobile or web app that tracks user workouts, exercise names, sets, reps, weights, and progress over time. The PRD includes detailed user stories, data models, and integration points (e.g., Supabase for database, React Native or Next.js for UI). With clear requirements, teams using AI builder platforms like Lovable or Cursor can rapidly scaffold and iterate, cutting delivery times from months to weeks. The PRD specifies measurable outcomes—such as boosting user retention by 30% in 3 months and logging 250 active sessions/day at launch.
Compared to alternatives
| Option | Best for | Trade-off |
|---|---|---|
| Lovable | PMs and devs who want to ship fast with React/Supabase scaffolding and instant multi-user support. | Requires comfort tweaking React/Supabase; less flexible on UI out-of-the-box. |
| Cursor | Developers who want precise code generation and granular control over Next.js or mobile codebases. | You’ll need more config upfront, and setup can take longer for authentication/storage. |
| Replit | Rapid MVPs and solo builders—easy to run, host, and iterate. Great for hackathons or learning. | Scaling, deployment, and database integration (e.g., production Supabase/Postgres) get tough after MVP. |
| Claude Code | Teams needing LLM-driven doc-to-code and quick iteration, with code completion and refactor support. | Limited direct scaffolding: you’ll stitch together code, not get the whole app instantly. |
| Bolt | AI-driven scaffolding for straightforward apps with workflows, especially when business logic is simple. | Lacks deep customization; better for CRUD/admin-type apps than consumer mobile products. |
A real example
Product Requirements Document (PRD) for WorkoutLog App
1. Overview
WorkoutLog is a cross-platform mobile app (iOS/Android) for individuals to track weightlifting or fitness routines. Users create workouts, log exercises/sets/reps/weights, and visualize progress over time. The goal: help 500 active users log at least 3 workouts/week within 4 weeks of launch and see a 30% increase in user retention MoM.
2. Target Users
- Gym goers (18–40, any gender) who track workouts manually or in spreadsheets.
- Personal trainers needing client workout tracking.
3. Core Features
- Create, edit, and delete workouts with multiple exercises.
- Add sets, reps, and weight for each exercise.
- View workout history chronologically and by exercise.
- Progress charts (e.g. line chart for squat 1RM over 8+ weeks).
- Account creation (email, Google OAuth).
- Data sync across devices (Supabase backend, real-time updates).
4. Nice-to-Haves (v2+)
- Social: share workouts or templates.
- Integration with Apple Health/Google Fit.
- Streaks/badges for gamification.
5. Non-Goals
- Nutrition tracking.
- Custom video-upload workouts.
6. Tech Stack
- React Native (Expo) for UI (mobile).
- Supabase for authentication, database, and sync.
- Vercel for web landing page (optional).
- Chart.js or Victory for graphs.
7. Success Criteria
- 250+ daily active users after 3 weeks.
- 1000+ total workouts logged in first month.
- 40% user retention at 30 days (tracked via Supabase analytics).
8. Example User Story
“As a user, I want to log tonight’s workout on my phone so that I can track progress week to week and see my strength gains.”
9. Page Flow
- Onboarding/signup
- Dashboard: recent workouts, CTA to log new
- Log workout: select exercises, enter sets/reps/weight
- View: History and progress
10. Open Questions
- Should the app suggest exercises or only allow custom entries?
- Priority: offline support vs more charts?
11. Metrics and Analytics
- Track user retention, session length, total logs/week, 7-day streaks completed. Success = 40%+ users logging 3+ workouts/week after 1 month.
This PRD is compatible with Lovable, Cursor, and Replit using the respective PRD guides.
How to use this
- Capture the core problem and scope: Define your use case (logging workouts), target user (e.g., gym goers), and exclude extras (like meal planning or video uploads). Keep the PRD focused: recording exercises, sets, reps, weights, and charts for progress.
- Pick your tech and AI builder fit: Decide if you want web (Next.js), mobile (React Native), or both. Match that with an AI builder: Lovable works fastest for Supabase-React projects; Cursor is great for Next.js code; Replit is solid for prototypes.
- Write crystal-clear user stories and feature lists: Draft example flows—logging a workout, seeing workout history, onboarding. Prioritize initial features and defer stretch goals to v2 (like social, notifications, integrations).
- Set success metrics and analytics upfront: Define at least two measurable goals (e.g. DAUs, retention, 1000+ total logged workouts in first month). List exactly how you’ll measure these—using Supabase analytics or custom event tracking.
- Draft your PRD in an action-ready format: Format your PRD with numbered sections—overview, target user, features, stack, metrics. Use our Filled Example as a template for clarity and completeness so AI builder tools like Lovable or Cursor don’t miss requirements.
- Plug your PRD into the AI builder of choice: Copy your PRD and use the 'starter prompt' provided for your chosen builder. For Lovable or Cursor, paste into their onboarding flow. For Replit, drop into Codegen. You’ll have your app scaffold within minutes.
FAQ
Which AI builder is best for a WorkoutLog app MVP?
Lovable is fastest for Supabase/React-based projects and ships good scaffolds for mobile-first apps. Cursor's great for customizing web-first Next.js versions. Replit is perfect if you want to iterate quickly or demo to stakeholders in under a day.
How much detail should my WorkoutLog PRD include?
Specify user stories, the full feature list, tech stack, and at least two measurable outcomes (e.g., daily active users and retention). Avoid marketing fluff—developers and AI builders need clear, concise direction to hit your intended target.
Can I use AI builders like Cursor or Claude Code for production apps?
You can. Cursor and Lovable both produce production-grade scaffolds when paired with frameworks like Next.js or React Native. You’ll need to review code, test, and handle deployment, but the heavy lifting is handled. Replit is best kept to MVP or learning builds.
How do I track app metrics like retention or active users?
With a Supabase backend, set up event tracking for each workout logged. Create daily/weekly queries to track active users, new signups, and streak completion. Surface charts directly in the admin panel for easy monitoring.
What if I want to add nutrition or community features later?
Flag stretch features as 'v2+' in your PRD. Ship with basic logging first, collect user feedback, then consider expanding into nutrition or community modules. Most AI builder architectures let you add features incrementally.