What heart rate variability is
Your heart does not beat like a metronome. The time between beats changes slightly from one beat to the next. Heart rate variability (HRV) measures that variation. Most watches report RMSSD in milliseconds. A higher number usually means your nervous system is relaxed and well recovered, and a lower number often goes with stress, poor sleep, illness or hard training.
Typical ranges by age
HRV falls with age and differs a lot between people, so your own baseline matters more than any table. These are approximate everyday ranges for RMSSD measured at rest or overnight. A study of healthy adults found an average of 42 ms with a normal spread from about 19 to 75 ms.
| Age | Typical RMSSD |
|---|---|
| 20 to 29 | 40 to 90 ms |
| 30 to 39 | 32 to 75 ms |
| 40 to 49 | 26 to 62 ms |
| 50 to 59 | 22 to 52 ms |
| 60 and above | 18 to 45 ms |
Different devices and times of day give different numbers, so always compare readings taken the same way, for example every morning or overnight average.
How to raise HRV
- Sleep seven to nine hours at regular times. Use the bedtime calculator.
- Do regular aerobic exercise and allow rest days.
- Limit alcohol, especially within four hours of bed.
- Practise slow breathing with the breathing timer.
- Manage stress and keep hydrated.