Heart rate variability (HRV)

• Garmin describes HRV as slight irregularity in the time between consecutive heartbeats.
• Wearables measure pulse rate variability (PRV) from the skin, used as a stand-in for HRV from an ECG.

Source: Garmin

• A 2026 meta-analysis of 43 studies: pooled absolute standardised error 0.188 for RMSSD and 0.134 for SDNN against ECG.
• Its authors say the findings should not be generalised to sleep, exercise, stress or everyday use.
• They also say the two methods are not shown to be interchangeable.
• A 2018 systematic review (Georgiou et al.) called the evidence inconclusive.

Source: Sensors, 2026, Folia Medica, 2018 (Georgiou et al.)

• Compare overnight or weekly HRV with your own recent average on the same device.
• A single low night is common.
• HRV well below your usual for weeks, with a higher resting rate, poor sleep or tiredness, is worth mentioning to a GP.

• HRV on a tracker is not a symptom; act on how you feel.
• NHS: call 999 for palpitations with chest pain, breathlessness or fainting.

Source: NHS

What is the difference between HRV and heart rate?

Heart rate is beats per minute. HRV is how much the time between beats varies from one beat to the next.

Is wrist HRV the same as HRV from an ECG?

A 2026 meta-analysis found close agreement in controlled studies, mostly at rest, but warned against assuming it holds during sleep, exercise or daily life, and said the methods are not shown to be interchangeable.

Can I compare my HRV with someone else's?

Not reliably. Values vary widely between people and devices, so compare against your own baseline on one device.

• Accuracy of Photoplethysmography-Derived Pulse Rate Variability Compared with Electrocardiography-Derived Heart Rate Variability - Systematic Review and Meta-Analysis, Sensors, 2026
• vivoactive 5 Owner's Manual - Body Battery, Garmin
• Heart palpitations, NHS
• Can Wearable Devices Accurately Measure Heart Rate Variability? A Systematic Review, Folia Medica, 2018 (Georgiou et al.)