HRV Reporting Reference Guide

Heart Rate Variability (HRV) in the Health app.

• Apple Watch uses the heart sensor to calculate HRV.
• Apple also lets you check heart rate in the Heart Rate app, including resting, walking, workout, and recovery rates.
• The Health app lets you browse categories and specific data types from the Search screen.

Report the HRV value shown in Health. Apple’s support pages reviewed here do not name the underlying HRV summary statistic, so do not convert it to a different metric.

Health app on iPhone → Search → Heart / Heart Rate Variability.

Sometimes the app shows heart-related data in the same general area, but heart rate and HRV are still separate fields. Record both if both are visible.

Heart Rate Variability (HRV) in Fitbit’s Health metrics / Vitals views.

• Fitbit says HRV is calculated with the RMSSD formula.
• In the redesigned app, the Health tab includes Vitals, previously called Health Metrics.
• Fitbit also shows a separate Readiness Score, which combines HRV, sleep, and resting heart rate.

Use the nightly HRV number from Health metrics / Vitals, checked after waking up.

Fitbit app → Today tab → Health metrics tile, or Fitbit app → Health tab → Vitals.

The Vitals screen is mainly for HRV, breathing rate, skin temperature variation, and resting heart rate. If the study also asks for heart rate, report the heart-rate value separately from the heart-rate screen or health tab.

No clearly exposed raw HRV value was found in the official Samsung Health support pages reviewed.

• Samsung Health can measure stress by checking heart rate and other factors.
• Samsung Health also shows Energy Score, which is based on sleep, blood oxygen, snoring time, skin temperature, and heart rate.
• Samsung’s support pages reviewed here do not give a clean participant-facing raw HRV screen path.

If your device only shows Stress or Energy Score, do not report those as HRV. Mark HRV as unavailable unless the app explicitly shows an HRV number.

Samsung Health → Stress, and the watch’s Heart rate widget for heart rate.

Heart rate is available in the Heart rate widget and Samsung Health heart-rate views. Stress is not HRV.

HRV Status for overnight HRV tracking; Health Snapshot for a separate 2-minute spot check.

• Garmin analyzes wrist heart rate readings during sleep to determine HRV Status.
• Garmin says the watch needs about three weeks of consistent sleep data to establish the baseline range.
• Garmin’s Health Snapshot is a separate session that reports heart rate, HRV, Pulse Ox, and respiration.

Use HRV Status for the overnight value unless the study specifically asks for a spot-check session. If your watch shows Health Snapshot, treat that as a separate capture, not the same thing as overnight HRV Status.

On the watch: HRV Status glance/widget, or end sleep when prompted. In Garmin Connect: HRV Status and trends.

Health Snapshot includes heart rate and HRV on the same report. HRV Status is an overnight HRV view, not a heart-rate screen.

Heart Rate Variability in Readiness and Trends. Oura also shows Average HRV and Max HRV.

• Oura measures HRV only during sleep.
• Oura takes five-minute samples through the night and reports the average HRV as the nightly value.
• The Trends screen shows the current day’s HRV at the top-left and longer-term averages in the chart.

Report Average HRV from Readiness or Trends. If you see Max HRV too, ignore it unless the study specifically asks for maximum HRV.

Oura app → Today tab → upper-left menu → Trends, or Readiness view.

For the same overnight window, use Resting Heart Rate from Readiness or Sleep detail views. Live Heart Rate is a separate daytime feature.

HRV in the Recovery view / Recovery dashboard. WHOOP also shows Recovery score, which is not HRV.

• WHOOP calculates HRV using a weighted average across the whole night of sleep, with more weight on slow-wave sleep and later stages of the night.
• WHOOP’s Recovery dashboard shows HRV, resting heart rate, and respiratory rate.
• WHOOP also has a Health Monitor area with live heart rate and other metrics in newer app layouts.

Use the overnight HRV from Recovery. Do not report Recovery score as HRV.

WHOOP app → Recovery tab / Recovery dashboard. In newer layouts, the Health tab can show live heart rate, while Health Monitor holds the recovery metrics.

Yes. The Recovery dashboard includes resting heart rate alongside HRV. If the study also asks for heart rate, report that separately.

Heart rate and the all-day heart rate curve are clearly documented. The official support pages reviewed here do not clearly expose a participant-facing raw HRV value.

• In Huawei Health, go to Devices, select the paired device, then Health monitoring → Continuous heart rate monitoring.
• Huawei says you can then view your all-day heart rate curve, including sleeping heart rate.
• The support pages reviewed do not give a clear raw HRV screen path for participants.

Report heart rate from the Huawei Health heart-rate screen. Do not substitute stress, sleep, or general wellness scores for HRV.

Huawei Health app → Devices → your device → Health monitoring → Continuous heart rate monitoring.

Yes. Huawei’s documented path is a heart-rate path. If the app does not explicitly show HRV, mark HRV unavailable.

Stress is the clearly documented Xiaomi metric, but Xiaomi says it is calculated using heart rate variability. The official support pages reviewed do not clearly expose a raw HRV value.

• In Mi Fitness, open Device → Stress.
• On the band, open the Stress app, then Settings for all-day pressure monitoring.
• Xiaomi says the stress feature uses HRV, but the displayed result is Stress, not raw HRV.

Do not report Stress as HRV. If the participant cannot find a screen that explicitly says HRV, mark HRV unavailable and report heart rate separately only if that is requested.

Mi Fitness app → Device → Stress, or the band’s Stress app.

No. Stress is the relevant Xiaomi screen, but it is still a derived score. Use the heart-rate screen for heart rate.