Question 1

What is a good HRV for my age?

Accepted Answer

Population medians for rMSSD: about 58 ms in your 20s, 46 in your 30s, 37 in your 40s, 29 in your 50s, 24 in your 60s, and 20 in your 70s. SDNN values run roughly 30–40% higher across every band. Anything within the 25th to 75th percentile for your age is considered typical.

Question 2

Why is rMSSD different from SDNN?

Accepted Answer

rMSSD measures short-term beat-to-beat variability and reflects parasympathetic (vagal) tone — most fitness wearables (Oura, WHOOP, Garmin, Polar) report this. SDNN measures total variability over a longer window — Apple Health uses this. The two are not interchangeable; comparing your SDNN to a friend's rMSSD is meaningless.

Question 3

Why does HRV decline with age?

Accepted Answer

Autonomic nervous system function declines gradually with age — vagal tone weakens, sympathetic dominance increases. The drop is steepest between the 20s and 40s, then continues more slowly. Aerobic fitness, sleep quality, and stress management can meaningfully slow the decline.

Question 4

Should I worry about a low HRV reading?

Accepted Answer

A single low reading is rarely meaningful — alcohol, poor sleep, illness, intense training, and travel all suppress HRV temporarily. A sustained downward trend across 7–14 days is the signal worth acting on. If you have known cardiovascular conditions, discuss persistent low HRV with your doctor.

Question 5

How can I improve my HRV?

Accepted Answer

The strongest evidence supports: consistent sleep timing, zone-2 aerobic training 3–5 days per week, slow diaphragmatic breathing, reducing alcohol, and minimizing late-day caffeine. Magnesium and omega-3 have moderate supportive evidence. Most people see measurable change within 4–8 weeks of consistent practice.

HRV by Age Calculator

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