Mainstay Consumer Health Data Privacy Policy
Effective Date: October 4, 2026 ยท Policy Version 1.3
This page is our consumer health data privacy policy. It is also a section of our full Privacy Policy, which covers everything else we collect.
This section is our consumer health data privacy policy, written for the Washington My Health My Data Act, Nevada's consumer health data law (SB 370), and similar laws. It applies to "consumer health data", meaning personal information that identifies, or could reasonably be linked to, your past, present, or future physical health. We apply it to every user, wherever you live.
What consumer health data we collect
- Health metrics from Apple Health: steps, distance, active calories, exercise minutes, heart rate, resting heart rate, heart rate variability, sleep, VO2max, body weight, and workout history, as daily summaries and workout summaries.
- Information you give us: age, sex, height, weight, injury and limitation notes, pain or soreness you report, check-in ratings for sleep, soreness, and motivation, post-workout feedback, and anything health-related you tell the AI coach.
- Information we derive: your readiness score and label, training adjustments made because of an injury or limitation, and fitness progress estimates.
Where it comes from
From you (what you type or select in the App), from Apple Health on your device (only the types you permit), and from our own calculations on that data.
Why we collect and use it
To provide the coaching you asked for: building and adjusting your training plans, writing coach replies, estimating your readiness, and showing your progress. We also use it to check and improve the quality and safety of the coaching (Privacy Policy, Section 7), to fix bugs, and to keep records the law requires. We never use it for advertising, and we never sell it.
Who receives it
We share consumer health data only with the processors that handle it on our behalf: Anthropic (to generate plans and coach replies), PostHog (AI observability traces, which contain the prompts above, and check-in ratings and pain reports in usage events), and Railway (hosting of our database). Sentry may receive health data only if it appears in a request that caused a server error. We have no affiliates that receive it, and we do not share it with any other third party.
Your consent
Before we collect consumer health data for AI coaching, current versions of the App show a consent screen that says what we send to Anthropic and how the Mainstay team reviews coaching, and nothing is sent to Anthropic until you agree. Beta testers on builds released before that screen existed agreed through the Beta Program Agreement and see the screen when they update. We will ask again before we collect or share consumer health data for any purpose not described here.
We never sell it
We do not sell consumer health data, and we do not use it to target advertising.
Your rights
- Confirm and access. Ask us whether we collect, share, or sell your consumer health data, get a copy of it, and get a list of every third party and processor that received it, with their contact details.
- Delete. Delete your account in the App (Profile > Membership and account > Delete account) or ask us to delete your consumer health data. We will also tell our processors to delete it, as described in the Privacy Policy, Section 13.
- Withdraw consent. Turn session recordings off in the App (Profile > Privacy > Session recordings, in current versions), or withdraw your consent to AI processing by emailing us or deleting your account. Once you withdraw AI consent we stop sending your data to Anthropic, which means the App can no longer coach you.
How to exercise them, and how to appeal
Email support@mainstay.fit from the email address on your account, or tell us which account is yours so we can verify the request. We will respond within 45 days; if we need more time (up to another 45 days) we will tell you why. We will not charge you or treat you differently for using these rights. If we decline your request, you can appeal by replying with "Appeal" in the subject line; we will answer the appeal in writing within 45 days and explain our reasons. If your appeal is denied, you may contact the Attorney General of your state (in Washington, the Washington State Office of the Attorney General; in Nevada, the Nevada Attorney General).