Parameter

Parameter is a workout app built around a simple idea: you already have a subscription to an AI that is a smarter coach than any fitness app's built-in one. Connect it once, and your AI plans your training using your goals, your equipment, and your real workout history, not a generic template. Parameter's job is to run what your AI writes and log it honestly: strength, intervals, classes, and rest, tracked on iPhone and on Apple Watch.

In a chat with your AI, you can ask things like:
- "Plan my week. I'm training for a 10K in six weeks and I lift Tuesdays and Thursdays."
- "I tweaked my knee. Adjust today's session."
- "Look at last month and tell me if my squat is actually progressing."

Your AI reads your profile, equipment, and history to answer, then pushes a plan or an updated workout straight into Parameter. You never touch a template or a spreadsheet, and Parameter never writes a plan on its own.

Parameter runs four kinds of training: guided classes you follow in another app, structured intervals with a live segment display and heart-rate-zone targets, exercise routines with a plate calculator and your last set shown before you lift, and simple sessions for a run, ride, or walk with indoor/outdoor tagging. Rest days get their own card, with active-recovery guidance, not an empty gap in your week.

On many machines that support the Bluetooth FTMS profile, Parameter sends each segment's authored targets to the equipment. On heart-rate-zone segments it also closes a loop to hold your zone, correcting speed on a treadmill and power on an indoor bike. It never chases your heart rate with incline. Starting and stopping a machine is always yours. Every interval workout also prints as a numbered console table, so a machine with no Bluetooth at all is still a first-class way to train.

Parameter's Apple Watch app works fully on its own, with its own sync, so a run or a lift is tracked wrist-only if that is all you bring. Whichever device starts a workout, the other shows the exact same execution screen, not just a status line, and pause, skip, end, and adjust all work from either wrist or phone. The Digital Crown adjusts your current target or your reps before you check off a set, and watch face complications and a Smart Stack card show what's next.

$1 a month, with a two-week free trial, is the only thing Parameter charges for, and it covers only the AI connection. Planning, execution, history, and a full data export stay free whether you subscribe or not. There's no Parameter account: your workouts, profile, and history live in your own private iCloud, and Parameter runs no database of its own to store them in.

Parameter works with any MCP-compatible AI client, including the assistants most people already subscribe to.

Parameter requires an iPhone running iOS 17 or later. An Apple Watch is recommended for live heart rate and wrist execution, but not required. Having a plan written by your AI needs an MCP-compatible AI client; building and logging your own workouts by hand works with no AI client at all.

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Privacy Policy: https://parameterfit.com/legal/privacy-policy/