I built this because I realized the 'VO2 Max' number in Apple Health doesn't tell you much without context.

I implemented the HUNT Linear algorithm (based on 55k participants) in a Next.js app to map raw VO2 max numbers to a 'Biological Age'.

I also added a /llms.txt endpoint so you can curl the documentation or let ChatGPT read the normative data tables directly without hallucinating.

It's a free web tool, but I also wrapped it in an iOS app for notifications/widgets if you want to track it long-term