FAQ

This is a great question and unfortunately we don’t know for sure. What we do know, is it’s an Apple or Apple Watch issue and not a ZonePRO issue. How do we know that? Because the same thing happens when you start a workout from Apple’s workout app. Therefore, when your Apple Watch takes several minutes to display your heart rate, especially during workouts or just after starting the Heart Rate app, it’s usually due to sensor acquisition delays or environmental/fit issues.

Here’s a breakdown of the most common causes:

1. Poor Wrist Fit or Sensor Contact

  • The sensor needs solid, consistent contact with your skin.

  • A loose watch or low on the wrist can make it struggle to get a reading.

  • Tighten the band slightly or move the watch higher on your wrist.

2. Cold Skin / Low Blood Flow

  • If your skin is cold (common when just starting exercise), blood flow near the surface is reduced, making it harder for the green optical sensors to detect pulses.

  • It usually improves as you warm up.

3. Motion Interference

  • Sudden wrist movement or arm flexing (e.g., during warmup) can disrupt readings.

  • Optical sensors are sensitive to erratic motion until the signal stabilizes.

4. Workout Start Delay

  • When you start a workout, the Watch begins looking for continuous readings.

  • It may take a minute or more to “lock on” and stabilize — this is expected behavior.

5. Background Sensor Prioritization

  • If another app is using the heart rate sensor (like a background fitness app), it might delay the primary reading you’re looking for.

6. Sensor Glitch or WatchOS Bug

  • Occasionally, bugs can cause delays. Restarting the watch or updating to the latest WatchOS often helps.

7. Tattoos or Darker Skin Tones (sometimes)

  • The green LED + photodiode method (PPG) can be less effective on dark tattoos or certain skin tones.

  • If this applies, using a chest strap (Bluetooth HR monitor) paired with the Watch is more accurate.

Tips to Improve Heart Rate Detection:

  • Wear your watch snug but comfortable

  • Start your workout a minute before actually exercising

  • Warm up your arms before checking HR in cold weather

  • Keep WatchOS and Health settings up to date

  • Use Airplane Mode toggle or restart if it seems stuck

ZonePRO does not read the heart rates from the Apple Watch sensor. Apple does not allow that. ZonePRO and all other apps that integrate with the Apple Watch read the heart rate data and all other health data from Apple’s Health App, ie. Apple HealthKit. If you think something is wrong, check Apple’s Health App. You’ll see the SAME results.

Open Apple Health app on your iPhone (white background with red heart, in dark mode it’s a black background). Select Show All Health Data, scroll to and select Workouts, next select Show All Data, select the specific workout, select Average Heart Rate.

This will list all your heart rate readings for your entire workout session. This is true for workouts started with ZonePRO or any other app, including Apple’s workout app.

What works sometimes is starting Apple Watch’s Heart App before starting ZonePRO.

This happens when you start your music from your iPhone. Next time start your music from the music app on your Apple Watch.