Simple Muscle
Connects to ChatGPT or Claude via MCP so your AI can create, adjust, and analyze your workouts
Simple Muscle gives your existing AI assistant (ChatGPT, Claude, or any MCP client) access to structured workout history so it can build a plan, swap an exercise around an injury, or analyze a month of training. The iPhone app runs the workout itself: one set at a time, with a rest timer, Live Activity, and lock-screen controls. Core tracking, the MCP connection, and offline use are free; $5/month adds iPhone cloud sync and backup, since Simple Muscle doesn't charge for the AI itself.
What holds up
- +Free tier includes unlimited workout tracking, Live Activity, and offline use on iPhone
- +MCP connector works with any AI assistant you already use — no built-in AI to pay for
- +Lock-screen Live Activity lets you complete sets and see the rest countdown without unlocking the phone
Mind the limits
- −Needs ChatGPT, Claude, or another MCP client to build plans — no plan builder in the app itself
- −Cloud sync and cross-device history cost $5/month; the free tier is iPhone-only tracking
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