Every wearable now tracks HRV. Whoop builds its entire recovery score around it. Oura features it prominently. Apple Watch added it to the Health app. But most people wearing these devices have no idea what HRV actually represents or how to use the data.
What Is HRV?
Heart rate variability measures the variation in time between consecutive heartbeats. If your heart beats at 60 BPM, that doesn't mean it beats exactly once per second. The intervals between beats vary slightly, maybe 0.95 seconds, then 1.05 seconds, then 0.98 seconds.
This variation is controlled by your autonomic nervous system and the balance between its two branches:
- Sympathetic (fight-or-flight): Speeds up your heart, reduces variability
- Parasympathetic (rest-and-digest): Slows your heart, increases variability
Lower HRV = more sympathetic activity = your body is stressed, fatigued, or fighting something.
What's a "Good" HRV?
This is where people go wrong. HRV is highly individual. A 25-year-old athlete might have an HRV of 80-120ms. A 50-year-old desk worker might sit at 20-40ms. Neither number is inherently bad.
What matters is your trend over time, not the absolute number.
General ranges (rMSSD, measured during sleep):
- Under 25: Below average for most age groups
- 25-45: Normal range for adults 40+
- 45-70: Normal range for adults 25-40
- 70-100+: Typical for fit, younger adults
Why HRV Drops
Your HRV will drop in response to:
- Hard training (especially if you trained late in the day)
- Poor sleep or not enough sleep
- Alcohol (even 1-2 drinks tanks HRV for 24-48 hours)
- Illness (often drops before symptoms appear)
- Stress and anxiety
- Dehydration
- Travel and jet lag
- Late-night eating
Why HRV Rises
Your HRV trends upward with:
- Consistent quality sleep
- Regular aerobic exercise (over weeks and months)
- Proper recovery between hard training sessions
- Stress management (meditation, breathwork)
- Good hydration and nutrition
- Cold exposure (cold showers, cold plunges)
How to Actually Use HRV Data
The Wrong Way
Checking your HRV every morning and panicking when it's low. Canceling workouts because your score dropped 5 points. Obsessing over daily fluctuations.
The Right Way
Look at the 7-day rolling average. A single day's reading means almost nothing. Your HRV naturally fluctuates by 20-30% day to day. What matters is the trend.
- 7-day average trending up: Your body is adapting well. Keep doing what you're doing.
- 7-day average trending down: Something is off. Look at sleep, stress, training load, or nutrition.
- Sudden large drop (30%+): Your body is fighting something. Consider reducing training intensity and prioritizing sleep.
Practical Decision Making
Use HRV alongside how you feel, not as a replacement for it:
- HRV is low but you feel great? Train normally but maybe skip the extra sets.
- HRV is high but you feel terrible? Listen to your body, not the number.
- HRV has been trending down for a week? That's a real signal. Dial back and recover.
"HRV is a useful signal, not a command. It should inform your decisions, not make them for you."
When to Measure
For the most consistent readings, measure HRV:
- First thing in the morning, before getting out of bed
- Or during sleep (Oura and Whoop do this automatically)
- At the same time each day
- After at least 5 hours of sleep
The Alcohol Effect
This deserves its own section because it's so dramatic. Even moderate drinking (2-3 drinks) can suppress HRV by 30-50% for up to 48 hours. If you track HRV, alcohol's impact on your body becomes impossible to ignore. Many people who start tracking HRV end up drinking less, simply because the data makes the cost so visible.
