SISU fitness club

Platform for gym management, personal training, and client progress tracking. It serves clients (workouts, nutrition, and progress tracking), gyms (manage clients, membership, and gym access), and admins (billing, updates, gyms management). Includes AI assistance, relative strength calculation.

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The Problem

Traditional fitness apps often exist in silos: workout trackers don't talk to nutrition apps, and trainers often rely on spreadsheets or WhatsApp to manage clients. Users struggle to interpret their own data—knowing that they lifted 100kg is different from knowing if that places them in an "Elite" category relative to their body weight. Trainers lack a centralized dashboard to monitor client adherence and health metrics efficiently.

The Solution

I built a unified platform with the following key features: Role-Based Dashboards: tailored interfaces for Clients, Trainers, and Admins. Smart Analytics: A proprietary algorithm, that calculates "Relative Strength" by comparing lifted weight vs. body weight, categorizing users from "Beginner" to "Elite" based on gender-specific standards. AI Integration: A context-aware AI chat assistant (powered by OpenAI) that remembers conversation history (for PRO users) and provides specific fitness/nutrition advice, including the ability to analyze uploaded images/videos of form. Automated Management: Background cron jobs handle membership expirations, billing cycles, and email operational emails. Gamification: Leaderboards and visual progress tracking (charts, muscle heatmaps) to drive user retention.

My Role

Full Stack Developer & Lead Architect

Tech Stack

Node.jsHTML2CanvasReact.jsMongoDBOpenAI APICloudinaryRenderGoogle OAuthNode-cronJWT

Key Decisions

1
Relative strength framework: Instead of just tracking raw numbers, I implemented a normalization layer that scores performance based on body weight. This required creating a massive static dataset of strength standards (GUIDE_RANGES) to give every user meaningful context for their lifts.
2
Context-Aware AI: I decided to implement a "memory" system for the AI chat (stored in MongoDB) specifically for PRO users, allowing the assistant to recall previous injuries or goals, making the interaction feel personalized rather than transactional.
3
Hybrid security approach: I used both JWT for API statelessness and Sessions for OAuth management, ensuring a smooth social login experience while keeping the API secure for mobile/external consumption.
4
Service worker implementation: To resolve issues with spotting connectivity in gyms, I implemented a Service Worker to cache core app shell assets, ensuring the app loads instantly even with poor signal.

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