Tutorial: Build a LangGraph AI Agent That Auto-Adjusts Workouts Using HRV Data

A developer tutorial published on DEV Community walks through building a self-optimizing fitness agent using LangGraph, the Notion API, and Apple HealthKit. The agent reads Heart Rate Variability data to assess a user's physical recovery state, then uses a GPT-4o-powered LLM to decide whether to reduce or maintain workout intensity. Based on that decision, the agent automatically updates the user's Notion workout database, replacing high-intensity sessions with active recovery when fatigue is detected. The system is structured as a state machine graph, allowing it to fetch additional context such as sleep data before finalizing any schedule changes. The tutorial requires Python 3.10+, LangChain, LangGraph, a Notion integration token, and a simulated or bridged HealthKit data source.