openGym

Product Introduction

1. Definition: openGym is a self-hosted, open-source workout tracking application (a Progressive Web App and native Android APK) designed for personal fitness data sovereignty. It falls under the technical categories of fitness software, personal health records (PHR), and self-hosted web applications.
2. Core Value Proposition: It exists to provide gym-goers and fitness enthusiasts with a privacy-first, subscription-free workout tracker that offers intelligent features like guided progression and an optional AI coach, all while ensuring users retain complete ownership and control over their training data.

Main Features

1. Guided Workouts with Intelligent Progression: The app pre-populates workouts based on your schedule and previous performance. It automatically calculates your next target weights or reps using customizable progression schemes (Linear, Greyskull LP, double progression). This works by storing your workout history locally or on your server and applying user-defined rules to determine the next session's parameters.
2. Optional, Private AI Fitness Coach: A key differentiator is the optional AI coach that runs on infrastructure you control. It uses the Model Context Protocol (MCP) and can connect to OpenAI, Anthropic, or Gemini APIs, or local models via Ollama. The AI analyzes your logged data (stalls, effort, body weight) to propose workout adjustments, but all changes require manual review and approval, keeping you in control. All queries are encrypted and private.
3. Comprehensive Exercise Library & Muscle Mapping: Includes a database of 1,324 exercises with animated demos, filterable by equipment and muscle group. The advanced muscle map provides three data-driven views: Volume Balance (where training load is distributed), Fatigue Tracking (weighted by perceived effort/RPE), and Strength Decay (time since last training for a muscle, linked to exercise 1RM). This is powered by exercise metadata and the user's logged set data.
4. Self-Hosted Deployment & Data Ownership: The core architecture allows for two deployments: a local-only Android APK or a self-hosted Docker container (for amd64/arm64). The self-hosted version enables multi-device sync via a personal server, passkey/Face ID login for multiple users, and ensures all data (workouts, body weight, photos) remains on infrastructure you control, with easy JSON export/import for backups.

Problems Solved

1. Pain Point: Eliminates reliance on subscription-based fitness apps that lock user data behind paywalls and often monetize user information. Solves data privacy concerns by ensuring zero telemetry and local/self-hosted storage.
2. Target Audience: Technically-inclined fitness enthusiasts (powerlifters, bodyweight trainees, gym-goers), homelabbers, privacy advocates, and small training groups (like friends or family) who want shared, synced logs without cloud dependencies.
3. Use Cases: Essential for users following complex, progressive routines (e.g., 5/3/1, Greyskull LP) who need automatic weight calculations; for individuals migrating from apps like Strong or Hevy who want to retain their history without fees; for coaches managing a few clients with full transparency; and for iPhone users seeking a functional home-screen app outside the App Store via the PWA.

Unique Advantages

1. Strengths & Limitations (Pros & Cons):

   • Pros: Unmatched data ownership and privacy (AGPLv3 licensed, no telemetry). Rich feature set rivaling premium apps (progression, AI analysis, muscle maps). Flexible deployment (offline mobile or self-hosted sync). One-time cost (free) versus recurring subscriptions.
   • Cons: Requires technical knowledge for self-hosting (Docker, reverse proxy). No official iOS App Store distribution, requiring use of the web PWA. Community support (Discord) versus dedicated commercial support. Feature development pace depends on open-source contributions.

2. Key Alternatives & Differentiation:

   • Strong/Hevy (Commercial Apps): These are polished, cloud-synced mobile apps with subscription models. openGym differentiates by being free, open-source, and allowing complete data export/self-hosting. It matches their core logging features while adding advanced analytics (structural balance, fatigue mapping) and a private AI coach.
   • FitNotes (Android): A popular free Android app with robust logging. openGym differentiates by offering cross-platform access via web/PWA, intelligent progression systems, a vastly larger exercise library with demos, and the self-hosted multi-user sync option.
   • Spreadsheets/Notion: The ultimate in flexibility and control. openGym differentiates by providing a specialized, guided UI that automates calculations (plate math, 1RM, progression), visual analytics (heatmaps, muscle maps), and structured workout planning, reducing manual entry and human error.

Frequently Asked Questions (FAQ)

1. Is openGym really free with no catch? Yes, openGym is completely free and open-source under the AGPL-3.0 license. There is no premium tier, subscription, or hidden fees. The developer accepts donations but does not monetize the software or user data.
2. Can I use openGym on my iPhone? While there is no native iOS App Store app due to Apple's restrictions, iPhone users can use the fully-functional self-hosted web version and install it as a Progressive Web App (PWA) to their home screen, which provides an app-like experience with offline functionality.
3. How does the self-hosting and data sync work? You deploy the openGym Docker container on a server (e.g., a home NAS or VPS). Users then access the web interface, create a profile secured with a passkey (like Face ID), and their workout data is stored in a database on that server, syncing automatically across all devices that log into that instance.
4. Is my data safe with the AI coach feature? The AI coach is designed for privacy. When enabled, it sends prompts to an AI endpoint you configure (like your own Ollama or a paid API). Your server only sends the necessary context (e.g., "user stalled on bench press"), and the AI's suggestions are never applied automatically. API keys are stored encrypted.
5. Can I import my history from other workout apps? Yes, openGym supports importing workout history from popular apps like Strong, Hevy, and FitNotes, as well as body weight data from Apple Health exports. The import function is designed to merge data intelligently without overwriting existing entries.