Privacy Policy

Strength IO is a strength-training app for iOS and watchOS operated by Crimson IO LLC ("we," "us," "our"). Your health data is yours — we built Strength IO to help you train smarter, not to monetize your information.

This Privacy Policy describes what information we collect, how we use it, and your choices. By using Strength IO, you agree to this policy.

Information We Collect

Account Information

Strength IO uses Sign In with Apple or email/password for account creation. When using Sign In with Apple, Apple provides us with an anonymized user identifier, and optionally your name and email address (Apple offers a relay option that hides your real email). Email sign-up collects your name, email address, and a password. We do not require or collect any other personal information to use the app.

Fitness & Workout Data

When you use Strength IO, the app stores data you create — including workout history, exercise logs, personal records, recovery scores, training metrics, gym profiles, goals, and preferences. This data is stored on your device and synced to our secure servers, tied to your account, so it is backed up and restores when you set up a new iPhone.

Workout summaries synced to our servers include aggregate metrics such as average and maximum heart rate, calories burned, duration, volume, and exercise details. We also sync your daily readiness score — the computed score only — so your readiness history is backed up and restores on a new device. The health readings behind that score (heart-rate variability, resting heart rate, sleep duration, respiratory rate, blood oxygen, wrist temperature, and their personal baselines) stay on your device and are never uploaded to our servers, and so does all raw HealthKit time-series data (individual heart-rate samples, sleep stage transitions, and other continuous readings). There is one exception: when AI coaching is enabled and your coaching text is written in Apple’s Private Cloud Compute, those daily readings and baselines are sent there to write it. They are not stored there, and they are never sent to our servers or to any third party.

Apple HealthKit Data

With your permission, Strength IO reads health data from Apple HealthKit to power its recovery and readiness features. This includes:

• Sleep (duration, stages, quality)
• Heart rate, resting heart rate, heart rate variability, walking heart rate
• VO2 Max
• Active energy, exercise time, steps, stand time
• Body measurements (weight, height, body fat, lean mass)
• Respiratory rate, blood oxygen
• Wrist temperature
• Workout history and effort scores

Strength IO may also write your completed workouts back to HealthKit so they appear in Apple Health.

Raw HealthKit data — individual samples, continuous time-series readings, and the daily health values behind your readiness score (heart-rate variability, resting heart rate, sleep duration, respiratory rate, blood oxygen, wrist temperature, and their personal baselines) — is processed on your device: it is never uploaded to our servers, never shared with third parties, never used for advertising or marketing, and never sent to any third-party AI service. The one exception to on-device-only processing is AI coaching: when it is enabled, the daily health values behind your readiness score (not the raw samples or time-series) are sent to Apple’s Private Cloud Compute to generate your coaching text, where they are not stored. Aggregate workout-level metrics (such as average heart rate per workout) and your computed daily readiness score are synced to our secure servers, tied to your account, so your history restores on a new device. You can revoke HealthKit access at any time in iOS Settings.

Location Data

If you grant location access, Strength IO captures your location once when a workout begins to tag that workout with a single pin — its coordinates and a reverse-geocoded place name (such as your gym). This is a one-time tag at the start of the workout, not continuous tracking and not a route. When location permission is granted, that pin is stored with your workout and synced to our servers as part of your workout data. There is no separate in-app sharing toggle: location is optional and controlled entirely by the permission you grant in iOS Settings — deny or revoke it there at any time and workouts recorded from then on will simply not include a location tag. Revoking applies going forward: pins already saved stay attached to the workouts that carry them, so your map history survives reinstalling the app. A pin is part of its workout, so deleting that workout deletes its pin, and deleting your account deletes all of them.

On-Device Processing & AI

Strength IO's recovery calculations run entirely on your device using Apple's on-device frameworks. Its AI coaching runs on your device, or in Apple's Private Cloud Compute — Apple's own stateless cloud infrastructure, built so that the data it processes is used only to generate your coaching text, is never stored, and is not accessible to anyone, including Apple. Your data is never sent to any third-party AI service for processing.

Analytics & Crash Reporting

We use service providers for analytics (to understand how the app is used) and crash reporting (to identify and fix bugs). These services collect usage data such as which screens you visit, which features you use, and technical information about crashes or errors. This data is associated with a random account identifier, not your name or email. We do not use advertising networks or ad-supported analytics services.

Subscription Data

Subscriptions are handled entirely by Apple's App Store. Strength IO verifies your subscription on your device using Apple's StoreKit — no third party receives your purchase data, and no purchase information is combined with your health or workout data. See the App Store terms for Apple's handling of payment information.

How We Use Your Information

We use your information to:

• Generate personalized workouts, weight recommendations, and recovery-aware scheduling
• Calculate daily readiness and recovery scores using your health and training data
• Track your progress, personal records, and training trends
• Authenticate your account
• Back up your data so it restores when you set up a new iPhone
• Monitor app stability and fix crashes
• Understand which features are used to guide development priorities

Service Providers

We use a limited number of trusted service providers to operate the app — for account authentication and data storage, and product analytics and crash reporting. These providers process data only as needed to provide their service and are contractually prohibited from using your data for their own purposes.

We do not sell, rent, or trade your personal data. We do not share your data with any third-party AI service — Strength IO's coaching runs on your device or in Apple's Private Cloud Compute, never through a third-party AI provider. We do not use advertising networks or share data for advertising or marketing purposes.

Data Storage & Security

Your fitness and workout data is stored on your device and synced to our secure servers, tied to your account and encrypted in transit and at rest.

Account information and your synced workout data are stored on secure servers with encryption in transit and at rest. We use industry-standard security measures including encrypted connections, secure authentication, and access controls. No method of storage or transmission is 100% secure, and we cannot guarantee absolute security.

Data Retention

Your account and fitness data is retained for as long as your account is active. You can delete your data at any time from within the app.

Crash reporting data is retained by our crash-reporting provider for approximately 90 days. Usage analytics events are retained by our analytics provider for longer under its standard retention policy; they are associated with a random account identifier, never your name or email, and after you delete your account they are no longer linked to any account profile.

Deleting Your Account

You can delete your account and all associated data at any time from Settings within the app. This permanently removes:

• All local app data on your device
• Your account and profile from our servers
• All workout, achievement, and training data stored on our servers
• Your authentication credentials

Two limited categories may persist after account deletion. First, administrative and security audit logs (records of privileged actions taken on the backend) are retained for security and legal-compliance purposes; any reference they held to your account identifier is cleared. Second, the usage and crash-reporting data described above is not linked to your identity: deleting your account deletes your analytics profile, and any remaining crash data (kept ~90 days) and usage events (kept longer under our analytics provider's standard retention policy) carry only a random identifier that no longer maps to any account. Neither category can be used to reconstruct your profile or fitness data.

You can also delete the app to remove all local data from your device.

Your Rights

You have the right to:

• Access the personal data we hold about you — the data export feature in Settings downloads the data the app holds, and you can contact us for a complete copy of everything stored on our servers
• Request correction of inaccurate data
• Request deletion of your data (available in-app or by contacting us)
• Revoke HealthKit access at any time
• Revoke location access at any time

California Residents

Under the California Consumer Privacy Act (CCPA), you have the right to know what personal information we collect, request its deletion, and opt out of its sale. We do not sell personal information. To exercise these rights, contact us at support@strengthio.app.

Children's Privacy

Strength IO is not intended for children under the age of 13. We do not knowingly collect personal data from children. If you believe a child has provided us with personal data, please contact us and we will delete it.

Changes to This Policy

We may update this policy from time to time. When we do, we will revise the "Last updated" date at the top of this page. Continued use of the app after changes constitutes acceptance of the updated policy.

Contact

Questions? Contact us at support@strengthio.app.