Privacy Policy — Z2/4×4 Trainer

Last updated: June 3, 2026

Z2/4×4 Trainer (“the App”) is a cardio training app for iPhone and Apple Watch that prescribes daily and weekly Zone 2 and Norwegian 4×4 workouts and weekly health-maintenance / weight-loss targets. This policy explains how the App handles your information.

Short version: The App is local-only. Everything stays on your device. We do not have a server, we do not collect your data, and nothing you enter or that the App reads from Apple Health is transmitted off your device or shared with anyone.

Who we are

• App: Z2/4×4 Trainer
• Developer contact: ozzyfly@logolo.ca

We are the developer of the App. We do not operate any online service, account system, or backend on your behalf.

What information the App uses

The App works entirely on your device. Depending on your choices, it uses:

1. Information you enter manually — age (to calculate maximum heart rate), an optional maximum-heart-rate override, body weight, and workout details.
2. Health data you choose to share via Apple Health (HealthKit), which the App can read: heart rate, resting heart rate, active energy (calories burned), body mass (weight), and workouts.
3. Workouts the App writes back to Apple Health: completed Zone 2 and Norwegian 4×4 workouts.

The App only requests the Health data types listed above, and only after you grant permission in Apple's standard Health permission screen. You can change or revoke this access at any time in Settings → Health → Data Access & Devices on your iPhone.

How your information is used

• All calculations — training zones (Zone 2 = 60–70% of max heart rate; 4×4 intervals at 85–95%), maximum heart rate (220 − age, or your override), and weekly targets — happen entirely on your device.
• Health data is used only to power these features inside the App.
• Workouts are saved back to Apple Health only so your training appears alongside your other health records.

What we do NOT do

• We do not collect, transmit, upload, or back up your data to any server. There is no server.
• We do not require an account, login, or registration.
• We do not sell, rent, trade, or share your data with any third party.
• We do not use any third-party analytics, tracking, advertising, or crash-reporting SDKs.
• We do not use your Health data — or any other data — for advertising or marketing, ever.
• We do not track you across apps or websites.

Apple's HealthKit framework prohibits using Health data for advertising or sharing it with third parties, and the App fully complies.

In-app purchases

The App offers an optional one-time purchase ("Pro"). The transaction is processed entirely by Apple through the App Store; the App never sees your payment details, and purchase verification happens on your device. No purchase information is linked to your Health or training data.

Data storage and security

• Your data is stored locally using Apple's on-device storage (SwiftData) and Apple Health.
• Data may be included in your personal device backups (iCloud Backup or encrypted local backups) if you enable those — controlled by Apple and your device settings, not by us.
• Because nothing is transmitted off the device, there is no online database to breach.

Deleting your data

• Health data: manage or delete records in the Apple Health app and in Settings → Privacy & Security → Health.
• All App data: simply delete the App. Workouts previously written to Apple Health remain there until you delete them — they belong to you.

Children's privacy

The App is intended for a general audience and does not knowingly collect data from anyone, including children. Because the App collects no data and has no server, no personal information is gathered regardless of the user's age.

Medical disclaimer

The App is a fitness and training tool, not a medical device. It does not diagnose, treat, cure, or prevent any disease. Consult a qualified healthcare professional before beginning any exercise program.

Changes to this policy

If this policy changes, we will update the “Last updated” date above and post the new version at the same URL.

Contact

Questions about your privacy or this policy? Email ozzyfly@logolo.ca.