Effective date: March 24, 2026 · Last updated: July 13, 2026
Contents
🔒 1. Overview
Sthenos ("the App", "we", "our") is a health and wellness application for iPhone and Apple Watch. This Privacy Policy explains what data the App accesses, how it is used, and the protections in place to keep your information private.
The short version: Sthenos reads health data from Apple Health on your device, processes it entirely on-device to compute your energy score, and never transmits your health data to any external server, cloud service, or third party. Ever.
📊 2. Data We Access
Sthenos requests read-only access to the following Apple HealthKit data types. All data is accessed and processed exclusively on your device.
| Data Type | Why We Use It | Stored? |
|---|---|---|
| Heart Rate Variability (SDNN) | Primary recovery signal, normalised to your personal baseline | On-device only |
| Resting Heart Rate | Recovery indicator and part of your personal baseline | On-device only |
| Heart Rate | Drives real-time activity and stress drain, and workout intensity | On-device only |
| Sleep Analysis & Stages | Sleep is the primary recharge window for your energy | On-device only |
| Workout Sessions | Used to compute training load (Banister TRIMP) and residual fatigue | On-device only |
You can grant or revoke any of these permissions at any time via Settings → Privacy & Security → Health → Sthenos on your iPhone.
🚫 3. Data We Never Collect
Sthenos does not collect, store, or transmit:
- Your name, email address, or any other personal identifiers
- Your location or GPS data
- Any health data to external servers or the cloud
- Device analytics, crash logs, or usage telemetry
- Advertising identifiers (IDFA)
- Any data from your contacts, camera, microphone, or photos
No account required. Sthenos works without registration. We have no user accounts and no user database.
⚙️ 4. How We Use Your Data
All data processing happens locally on your iPhone and Apple Watch. Specifically, the App:
- Reads health samples from HealthKit and replays them through an on-device energy model to compute your Sthenos score (0–100)
- Stores a rolling 30-day history of your scores in local app storage to power trend graphs and personalised baselines
- Caches your most recent score in a widget extension so it can be displayed on your Home Screen and Lock Screen without opening the App
- Sends your current score to the Apple Watch companion app over local device communication (never the internet)
- On supported devices, optionally generates written insights using Apple Intelligence. This runs entirely on-device — your health values are used only in the on-device prompt and are never sent to Apple or any server.
None of this data ever leaves your device.
🤝 5. Third Parties
Sthenos does not integrate any third-party SDKs for analytics, advertising, crash reporting, or data collection.
The App uses Apple HealthKit (provided by Apple Inc.) to read health data. Your use of HealthKit is governed by Apple's Privacy Policy. Sthenos does not share any HealthKit data with Apple beyond what Apple already has through HealthKit itself.
There are no advertisements in Sthenos and we do not share your data with advertisers, data brokers, or any other commercial third parties.
👶 6. Children's Privacy
Sthenos is rated 4+ on the App Store. The App does not knowingly collect any personal data from children under the age of 13. Because Sthenos does not collect any personal data from anyone, it is safe for use by users of all ages under parental supervision.
⚖️ 7. Your Rights
Because Sthenos does not collect or store personal data on any server, there is no data to request, export, or delete from our side. However:
- Revoke HealthKit access: Go to Settings → Privacy & Security → Health → Sthenos and toggle off any data types at any time.
- Delete local app data: Deleting the Sthenos app from your iPhone removes all locally stored scores and history from your device.
- Apple Health data: Your underlying health data is managed through the Apple Health app. Sthenos has read-only access and cannot modify or delete your health records.
If you are a resident of the European Union (GDPR), California (CCPA), or another jurisdiction with specific privacy rights, those rights are fully satisfied by the above — since we hold no personal data about you.
📝 8. Changes to This Policy
If we make material changes to this Privacy Policy, we will update the effective date at the top of this page and, where appropriate, notify you via an in-app notice.
Continued use of Sthenos after any changes constitutes your acceptance of the updated policy. We encourage you to review this page periodically.
✉️ 9. Contact Us
If you have any questions or concerns about this Privacy Policy or how Sthenos handles your data, please get in touch.
Questions about your privacy?
We're happy to help. Send us an email and we'll respond within 48 hours.
bursts.mansard-0v@icloud.com