Your Apple Watch, Meet Your Coach

Big news for iPhone users. With the latest iOS app update, Apple Health is now a first-class data source in IntervalCoach — so anything that ends up in HealthKit (your Apple Watch, an Oura ring, a Withings or Garmin Index scale, a period tracker, Garmin or Polar via their auto-sync apps) can now feed the coaching engine directly.

If you wear a Garmin, Polar, or Wahoo, your wellness has always flowed into IntervalCoach via Intervals.icu — that isn't changing. What's new is the Apple Health path, which is the simplest way in for anyone whose data lives in HealthKit instead of ICU: one toggle in Settings, no third-party scripts, and you mix sources freely (sleep from Oura, weight from Withings, HRR from your Watch — IntervalCoach stitches them into one daily wellness record).

Update your IntervalCoach iPhone app and enable Apple Health in Settings to turn it on.

What the app now reads

Eleven metrics come straight from Apple Health into your daily coaching:

• Heart rate variability — overnight HRV from your Apple Watch, the single most informative recovery signal we have.
• Resting heart rate — your morning RHR, elevated when you're not fully recovered.
• Respiratory rate — breaths per minute during sleep, another autonomic marker.
• Blood oxygen (SpO₂) — persistent drops can flag altitude adaptation or illness.
• Wrist temperature — Apple Watch Series 8 and later track overnight temperature deviation, the same signal Whoop uses.
• Sleep duration and phase breakdown — total hours plus REM, deep, and core sleep. A 7-hour night with 30 minutes of deep sleep and a 7-hour night with 2 hours of deep sleep say very different things about recovery.
• VO₂ Max — Apple's cardio fitness estimate, calculated from your outdoor runs and walks. A slow-moving indicator of aerobic fitness that complements your eFTP progression.
• Heart rate recovery — how fast your heart rate drops in the first minute after peak effort. Slow HRR is a classic sign of parasympathetic under-reactivity and pairs well with HRV for catching accumulated fatigue.
• Body weight and body fat percentage — from any Health-compatible scale.
• Menstrual cycle — auto-detected when you log your period in Apple Health, so your coach has cycle context without a separate check-in.

All of this feeds IntervalCoach's readiness pipeline — personal baselines, multi-day trend detection, fatigue signals, training adaptations. It's the same engine we've used from day one to turn raw wellness numbers into concrete coaching decisions, and it's source-agnostic on purpose: whether your data comes from an Apple Watch, a Whoop strap, or an Oura ring syncing through Apple Health, the detectors, the baselines, and the adaptations are identical. The coaching is ours; the wearable is yours to choose.

How it works in practice

Enable it once. Open the IntervalCoach iPhone app → Settings → Apple Health → toggle Sync on. You'll see the standard Apple permission sheet; grant access to the types you're comfortable sharing. The app handles the rest.

It syncs automatically. iOS wakes the app in the background when your Watch writes a new sleep session or morning heart rate recovery. By the time you open the app in the morning, your dashboard already reflects last night.

There's a manual button too. "Sync now" in Settings pushes the latest values immediately — useful right after enabling, or when you want to verify data is flowing.

Multiple sources, one unified view. Lots of athletes wear more than one device — a sleep tracker, a sports watch, a connected scale. IntervalCoach merges everything into a single daily wellness record per athlete instead of letting sources fight over the same metric. Each field has a clear priority so you don't end up with drift between sources, duplicate data, or the app confused about which HRV reading is "real". Add or remove a device whenever — the coaching picture adjusts without losing history.

Your Intervals.icu dashboard stays in sync. Everything Apple Health provides that Intervals.icu can store (HRV, resting HR, sleep, SpO₂, respiration, body weight) is mirrored there automatically. Your training platform stays the single source of truth for your history.

What shows up in coaching

The new data doesn't just sit in a log. It feeds the detectors that drive your readiness score and the Coach+ chat:

• HRV dropping below your personal baseline → elevates fatigue risk, may suggest a lighter day.
• Heart rate recovery slowing vs your 14-day average → flags sympathetic dominance, a subtle overreaching signal that HRV alone can miss.
• VO₂ Max declining against your 30-day peak → a sustained drop, together with chronic fatigue signals, is an early warning for burnout.
• Sleep score and sleep debt → your coach knows when you're running on a deficit and adjusts tomorrow's intensity accordingly.
• Menstrual phase → currently surfaced as info-level context; we're building phase-aware signal interpretation next (luteal-phase HRV dips, for instance, shouldn't read as fatigue).

If you want the full story behind these decisions, we've covered the coaching engine in depth elsewhere: How IntervalCoach Adapts Your Workout Every Day walks through the morning pipeline that turns these signals into concrete workout changes; HRV-CV: What Volatility Tells You That HRV Alone Does Not explains why we care about HRV stability, not just today's number; and The Science Behind IntervalCoach documents the published research behind every threshold. Apple Health simply widens the set of athletes that can feed this engine — the engine itself hasn't changed.

What else is new in this update

While we were in iOS land, a few other improvements shipped:

• Dashboard, Calendar and Training Plan now refresh automatically when you reopen the app. No more switching tabs to pick up the workout you just completed on your Watch.
• Calendar holiday events now look like calendar markers, not activities. "Summer vacation" no longer shows up with the same orange icon as your morning walks.
• Week view crosses month boundaries correctly. If a month starts mid-week (April 1 on a Thursday, say), the preceding Monday–Wednesday from the previous month now load automatically.

What's next

One thing already on the build list: importing non-Intervals.icu workouts from HealthKit — gym sessions, yoga, walks, hikes, anything your watch records outside your usual cycling/running platform. Today, activities that don't land in Intervals.icu don't contribute to your load picture; with HealthKit as an import source they will.

More broadly, we're pushing hard to bring the iOS app on par with the web app. The web surface has had a head start, so a few things are still web-only today — the full Analytics page (fitness trend, power/pace history, progressive overload tables), Settings for training preferences and subscriptions, goal-event setup, and a handful of Coach+ tools. Every iOS release is closing that gap, and the eventual goal is simple: whichever surface you open, you see the same picture of your training.

If you've been waiting for a way to get recovery-aware coaching without forcing another device into your setup, this is it. And if you're already connected through any of the existing paths, nothing breaks — Apple Health just becomes another source the coaching engine can learn from.