Privacy Policy

Flex (flex.attereon.com, the iOS/iPadOS app on the App Store, and the Android app on Google Play, with companion apps for Apple Watch and Wear OS) · Last updated September 16, 2026

What we collect

• Account data: you sign in with your Attereon account (id.attereon.com), which holds your email address and password; Flex's own servers never store your password. Flex keeps a profile linked to that account: a username, an optional display name, and a public-profile flag if you enable a public profile.
• Fitness data you create: workout plans, logged sets/reps/weights, session history, yoga and recovery sessions, favorites, preferences (music, trainer voice, units), and, if you fill it in, a training profile (goals, injuries, experience) for a trainer. This data exists so the app can function — tracking your training is the product.
• About you (optional): body weight, height, birth year, and sex, if you choose to enter them in Settings. They exist only to estimate calories and heart-rate zones for your own sessions. They are never shown on a public profile and never shown to a trainer. Clear any field at any time.
• Device push tokens (native apps only, with your permission): a push token from Apple (APNs) on iOS or Google (Firebase Cloud Messaging) on Android, so we can deliver notifications such as trainer plan assignments and messages. A notification passes through Apple's or Google's push service on its way to your device. Declining notifications disables only this.
• Apple Health and Apple Watch (iOS app only, off until you turn it on in Settings): with your permission, each finished workout or yoga session is written to Apple Health as a workout, and we read the heart rate and active energy Health recorded during that session (for example from an Apple Watch) plus your latest body weight to estimate calories. If you install the Apple Watch companion app, a session started on your iPhone can run on the watch too; the watch streams your live heart rate to the phone for the session and nowhere else. A summary of that session — average and peak heart rate, calories, and the heart-rate trace — is stored with the session in your Flex history so it appears on every device. Health data is used only to show you your own sessions: never for advertising, never shared, and deleted with your account. Turn the switch off at any time; you can also revoke access in the Health app under Sharing.
• Health Connect and Wear OS (Android app only, off until you turn it on in Settings): the Android counterpart of the above. With your permission, each finished workout is written to Health Connect as an exercise session (a yoga breathing practice as a mindfulness session, where your version of Health Connect supports it) together with the heart-rate readings and active calories from that session; we read the heart rate and active calories Health Connect recorded during the session (for example from a Wear OS watch) plus your latest weight to estimate calories, and a body weight you enter in Flex is written back to Health Connect. The permissions requested are: read and write heart rate, read and write active calories burned, read and write weight, write exercise sessions, and write mindfulness sessions. If you install the Wear OS companion app, the watch streams your live heart rate to the phone for the session and nowhere else. The same session summary described above is stored in your Flex history. Turn the switch off at any time; you can also revoke each permission in Health Connect (Settings → Apps → Health Connect → App permissions).

What we don't do

• No third-party analytics SDKs, no advertising networks, no fingerprinting, no selling or sharing of personal data with data brokers. The only outside services that handle anything from the app are Apple and Google, to deliver push notifications to your device, and only if you allow notifications. Our public pages (the homepage, Learn library, and these pages) collect anonymous, aggregate visit statistics using our own self-hosted system — no cookies, no third parties, and nothing that can identify you or follow you across days or sites. Inside the app, once you are signed in, the only record of how you use it is the gear-recommendation events described below.
• No collection of contacts, location, photos, or anything outside what you enter in the app and, if you opt in, the Apple Health or Health Connect session data described above.
• Guest mode works without an account; guest workout data stays on your device.

Gear recommendations and affiliate links

Some screens may show a gear recommendation that links to Amazon. As an Amazon Associate we earn from qualifying purchases. Which product you see is chosen on our servers from your own recent training in Flex — for example the equipment you have been logging with and the weights you are lifting — and nothing about you is sent to Amazon or anyone else to make that choice. When a recommendation is shown or tapped, we record an event on our servers: the product, the screen it appeared on, whether it was shown or tapped, and your user id (no id if you are signed out). These events rotate what you see and tell us which recommendations are useful; there are no third-party ad networks or trackers involved, and when your account is deleted the events are detached from it (the user id is cleared), leaving nothing that identifies you. Once you tap through, these are ordinary outbound links and Amazon's own privacy policy applies on their site.

Where data lives

Your data is stored on our servers (DigitalOcean, USA) over HTTPS. Login sessions use rotating tokens stored on your device.

Trainers

Nothing is shared with a trainer until you join one with their code and they approve you. From the date of approval, an approved trainer can see: every workout, yoga, and recovery session you complete — not only the plans they assigned — including each logged set, rep, and weight; your personal records and progress per exercise; how your sessions line up with the plans they assigned; the training profile you fill in (goals, injuries, experience); and the comments either of you leave on a session. The heart-rate and calorie summary on a session is visible to a trainer only while "Share health data with my trainer" is on in Settings. Your body weight, height, birth year, and sex are never shown to a trainer. Trainers can keep private notes about their clients on their side; those are not shown to you. Leaving a trainer in the app ends their access.

Your control

• Edit or delete logged workouts and plans at any time in the app.
• Export everything we hold about you from Settings as one CSV file with a section for each: your profile, body-weight readings, every session (strength, yoga and recovery, with the heart-rate and calorie summary where one was recorded) and every logged set. If anything is missing from it, email [email protected] from your account's address.
• Account deletion: from Settings (type your username to confirm) or via [email protected]. This permanently deletes your Flex profile and everything stored under it — plans, sessions and logged sets, health summaries, body-weight readings, training profile, favorites, comments, shared plans, awards, and push tokens. Your Attereon account itself is not affected, and can be linked to a fresh Flex profile later.
• Log out anywhere to revoke that device's session server-side.

Children

Flex is not directed at children under 13, and we do not knowingly collect their data.

Changes & contact

Material changes to this policy will be posted here with a new date. Questions: [email protected].