Measurement Frequency & Manual Measurement

Automatic Measurement Frequency

Under normal circumstances, Apple Watch automatically measures HRV every 2 to 5 hours. StressMonitor reads this data from Apple Health — it does not independently control sensor sampling.

Apple Watch pauses automatic HRV monitoring when:

• Low Power Mode is enabled
• A workout session is active
• You are in a high-movement state
• The watch is not worn securely or is locked
• watchOS 7 or earlier is installed

Note: As developers, we cannot adjust the Apple Watch's built-in HRV monitoring frequency.

Increasing Monitoring Frequency (Optional)

For users outside mainland China, you can prompt Apple Watch to check HRV every ~15 minutes by enabling AFib History:

1. Open the Health app on iPhone → Heart → AFib History → Enable
2. Open the Watch app → Heart → AFib History → Enable

Be aware this increases battery consumption. This is currently the only way to increase Apple Watch HRV sampling frequency.

Manual Measurement

To trigger an immediate HRV reading:

1. Open the Mindfulness app on your Apple Watch
2. Start a Breathe session — select 3 minutes or longer for accuracy
3. Ensure the watch is fitted snugly; keep your body still and breathe naturally (don't follow the guide rhythm)
4. After the session completes, lock then unlock your iPhone
5. Wait about 1 minute — StressMonitor will receive the data and update

Due to Apple Watch limitations, data may occasionally take longer to appear. If it hasn't updated after 30 minutes, try again later.

Best Time to Measure Manually

We recommend measuring within 10 minutes of waking up, before food, coffee, exercise, or social activity. This captures your true baseline state.

Ideal conditions:

• Sitting or lying down
• Minimal physical activity
• No recent large meals, alcohol, or caffeine
• Emotionally calm

When to Avoid Manual Measurement

• Within 30 minutes of intense exercise (elevated HR interferes with results)
• When emotionally charged or stressed
• After consuming alcohol or caffeine
• After smoking or taking medication affecting heart rate

Why Data May Appear Stale

HRV is most meaningful over longer sampling windows. If you check mid-afternoon without a recent rest period, the reading reflects an earlier measurement — this is expected behavior, not a bug.

If data hasn't updated for more than half a day, check:

• iPhone and Watch are connected
• Background App Refresh is enabled for StressMonitor
• Apple Watch has recent heart rate data in the Health app