Your strength coach, built into your Apple Watch.
VolumeArc is an AI-powered strength coach for iPhone and Apple Watch. The watch leads the session. Readiness comes from your real recovery data. Your history follows you across every Apple device — privately, and on-device when it matters.
Built day-one on iOS 26 + watchOS 26
- iOS 26
- watchOS 26
- Live Activities
- Foundation Models
- CloudKit
- Liquid Glass
Three things VolumeArc does that other strength apps don’t.
On-device AI that works offline. A watch app that doesn’t need your phone. Readiness driven by your real recovery data, not a survey.
You
Last week I hit 5×5 at 225. Should I push to 230 today or hold?
VolumeArc · Pro
HRV is up 6% vs your 28-day baseline and you slept 7h42m. Push to 230×5×5. If bar speed slows on set 3, drop to 225 for the last two — log RPE so I can recalibrate next session.
AI coach with on-device fallback
A three-tier provider chain. Premium routes to Gemini Pro via streaming SSE. Free routes to Gemini Flash Lite. Both fall back to Apple Foundation Models on-device when the network drops, then to a heuristic engine offline. Every prompt is template-validated against a 20-fixture eval matrix.
Rest timer
1:23
Bar speed: target met
Apple Watch as the primary surface
Start, log, and finish a session entirely from the watch — real HKWorkoutSession, native rest timer, set decisions, coach cues. Offline payload queue replays to the phone the moment connectivity returns.
Readiness
82
out of 100
Readiness from real recovery data
Five-factor readiness score derived from HRV trend, sleep debt, training load, recovery, and recent volume — all from HealthKit. The coach reads this context before answering, so the prescription matches the body that opened the app.
Built native to your devices, not ported to them.
Every system VolumeArc touches uses the right Apple API for the job — HealthKit, CloudKit, ActivityKit, App Intents, Foundation Models, and the iOS 26 design system.
Live Activities + Dynamic Island
Active workouts publish to the lock screen and Dynamic Island with real session state — exercise, target, rest timer countdown.
Apple Watch parity
Real HKWorkoutSession on the watch — start, log, finish without your phone. Offline payload queue replays when reconnected.
Privacy-first AI
On-device Apple Foundation Models tier means your coach can answer without ever leaving your phone. Cloud tier ships with PII scrubbing.
CloudKit sync
Your training history syncs across iPhone, iPad, and Watch via your private CloudKit container. No accounts, no third-party servers.
Siri Shortcuts + App Intents
Six App Intents cover the common flows — start next workout, ask coach, log set, sync. Wire them into Shortcuts or Focus filters.
Liquid Glass design
Built on day one for iOS 26’s Liquid Glass material system. Cards, toasts, coach bubbles, and hero transitions feel native to the OS.
Simple pricing. Subscription auto-renews under App Store rules.
Free covers the full tracker, sync, and on-device AI. Pro unlocks Gemini Pro and live voice coaching.
Free
$0
Track every set, every workout. Get the coach on Gemini Flash Lite + on-device Foundation Models. Cloud sync across all your Apple devices.
- Full workout tracker
- Apple Watch app + complications
- Live Activities + widgets
- Cloud sync (CloudKit private DB)
- AI coach — Flash Lite tier
- On-device Foundation Models fallback
- Readiness from HealthKit (HRV, sleep, training load)
Pro
$9.99/mo
The full AI coach experience — Gemini Pro tier and live voice coaching. For lifters who want the deepest prescription their data can give them.
- Everything in Free
- AI coach — Gemini Pro tier
- Single-turn voice coaching
- Curated programs library (5/3/1, PPL, SS)
- Priority eval-trend updates
- Apple Watch Vitals + Training Load integration
Subscriptions are billed through your Apple ID. Auto-renews until cancelled. Manage in iOS Settings → Apple ID → Subscriptions. See Terms and Privacy Policy for full disclosure.
Frequently asked questions
Anything else? support@volumearc.com.
How is VolumeArc’s AI coach different from a chatbot?
VolumeArc’s coach runs through a structured prompt template — system persona, intent envelope, and a context block built from your readiness, recent sessions, and current program. Every prompt is regression-tested against a 20-fixture eval matrix before it ships. We publish the eval results at /quality.
Does the AI coach work offline?
Yes. On supported devices (iOS 26+ with Apple Intelligence enabled), the coach falls back to Apple’s on-device Foundation Models when the network is unavailable, so you can still get readiness-aware advice in the basement gym, on a plane, or anywhere there is no signal.
What data does VolumeArc send to its servers?
Workout history and personal information stay in your private CloudKit container — Apple holds the encryption keys, not us. The AI coach forwards a redacted prompt envelope to a Cloudflare Worker that proxies to Gemini Pro or Flash Lite. We strip personally identifying fields before any payload leaves the device. Read the full Privacy Policy for the data-flow diagram.
Why is the Apple Watch experience first-class?
Most strength apps treat the Watch as a notification surface. VolumeArc runs a real HKWorkoutSession with a native rest timer, set logging, coach cues, and offline payload queueing. The Watch can run a session start-to-finish even when your phone is off.
What does Premium unlock?
Premium ($9.99/month or $79.99/year) routes the coach to Gemini Pro for deeper context handling, unlocks single-turn voice coaching, and gates priority features. Cloud sync, on-device AI, Live Activities, and the full workout tracker stay free for everyone.
Will VolumeArc come to Android or the web?
No. VolumeArc’s wedge is being the deepest Apple-ecosystem strength coach. Cross-platform tools chase breadth; VolumeArc trades breadth for depth so the Watch + Live Activities + Health integration can be best-in-class.
How do you handle HealthKit data?
HealthKit reads (HRV, sleep, training load) feed the Readiness model and the coach prompt. Your raw HealthKit data never leaves the device. Computed summaries (e.g., "HRV down 8%") may be included in the redacted coach prompt envelope, but only with explicit permission and only when you ask the coach a question.
Can I import my workout history from another app?
Today, VolumeArc imports anything Apple Health already has — completed strength sessions logged by other apps, manual workouts, and cardio context. Direct Hevy / Strong / Fitbod imports are on the roadmap.
I have a problem or feedback. How do I reach you?
Use the in-app Send Feedback flow under Profile → Help, or email support@volumearc.com. Bug reports include redacted diagnostics so we can reproduce the issue without seeing your personal data.