Apple Health Sync: AI Coaching From Apple Watch

Hey, I'm Martin, the founder of Coach. Fun update today: Apple Health sync is finally live. Our Garmin integration has been running for a while, and now everyone on Apple Watch and iPhone gets the same depth.

What syncs from Apple Health

Connect once and Coach pulls in:

• Workouts with the full heart rate trace (every sample your watch recorded), laps, distance, and calories. Not just a summary line.
• Heart rate and heart rate variability (HRV), the signals your recovery is built on. Apple Watch records HRV as SDNN, the standard deviation of the intervals between normal beats.
• Sleep, split into deep, core, REM, and awake stages. Core is what most other platforms call light sleep, and that is how Coach labels it.
• Daily metrics like steps, resting heart rate, and active energy.

My favorite part: we backfill up to a year of workout history and 90 days of daily health metrics. Your coach knows how you've been training before you've typed a single word.

Every workout your Apple Watch records shows up, native Workout app or third-party. All 84 of Apple's HealthKit workout types, including the three Apple has since deprecated but older workouts still carry, map into the same sport taxonomy we use for Garmin, so "Functional Strength Training" lands in the right bucket instead of a generic "Other." And we keep your Apple data in full, so when Coach gets smarter at reading a session, we re-run the analysis across your whole history. No re-syncing. It just quietly gets better.

What your AI coach does with the data

Real heart rate and HRV let Coach read your recovery instead of guessing at it. If your HRV is suppressed and last night's sleep was short, Coach can turn tomorrow's hard intervals into an easy aerobic day on its own, instead of holding you to a plan your body already voted against.

That is not a gimmick. In Vesterinen and colleagues' 2016 trial, recreational runners who did hard sessions only when their HRV was in its normal range improved 3,000 m speed by 2.1% over eight weeks while doing about a quarter fewer hard sessions than the group on a fixed plan, whose 1.1% gain was not significant. Kiviniemi's 2007 study found the same pattern in moderately fit men: HRV-guided training raised maximal running speed more than a predefined schedule did. Sleep is part of that picture. A 2025 meta-analysis of 11 randomized trials found sleep deprivation reliably lowers rMSSD, the vagal HRV index, and shifts the balance toward sympathetic drive.

Want the science? We've written about heart rate zone training, recovery and sleep tracking, and the training load model behind it. Short version: the more honest data Coach has, the less it assumes.

What's next

Apple Health is the second provider Coach reads, after Garmin, and it runs through the same normalization step and the same analysis. That shared core is what makes the next sources of your training data faster to add, and there are more on the way. Referrals are next: share Coach with a friend, and there's something in it for both of you. And a big chunk of the last stretch went into performance and bug fixes, the unglamorous work that makes an app worth trusting. We'll keep doing it.

Connect Apple Health in Coach

Open the Coach iOS app, connect Apple Health, and grant access. A few taps, and your coach gets a year of context in return. That's the whole ask.