Your heart doesn't beat at perfectly even intervals. Even at a steady 60 BPM, the time between individual beats varies slightly — 0.95 sec, 1.02 sec, 0.98 sec, 1.05 sec. That variation is HRV, and it reflects how your autonomic nervous system is balancing rest-and-recovery against fight-or-flight.

Higher generally means more parasympathetic (recovery) influence. Lower means more sympathetic (stress) influence. Useful signal. Easy to misread.

The Single Most Important Thing

Your baseline matters more than absolute numbers. Two healthy 35-year-olds can have HRVs of 40ms and 75ms and both be perfectly fine — different anatomy, different baselines. Compare yourself to yourself, not to a friend, an influencer, or a population average.

What Lowers It

The factors that show up most. They compound.

Sleep · the biggest lever

One bad night drops HRV substantially. Cumulative sleep debt compounds it. For most adults, sleep optimization is the highest-leverage HRV intervention — full stop.

Alcohol · the underrated one

Even a few drinks can suppress HRV for 24-48 hours. Dose-dependent, hits even when sleep duration looks normal. The most reliable explanation for an unexpectedly low morning reading.

Hard training · expected, temporary

A hard session acutely drops HRV. Normal — that's the recovery cost. Should rebound within 24-48 hours. Sustained suppression over multiple sessions is the signal something needs attention.

Hydration · often overlooked

Dehydration suppresses HRV. Athletes in heat, anyone after a heavy session — proper hydration is one of the easier wins, and people consistently underrate it.

Stress · the long-tail one

Work, relationships, finances, illness — chronic life stress sustainably suppresses HRV regardless of source. Often the thing people are least willing to address. Usually the thing causing the most damage.

How To Read It

Trends, not single readings.

1 · One bad reading isn't a problem

Day-to-day noise is real and large. A single low number tells you almost nothing. Use rolling 7-day averages and look at the trend, not the daily blip.

2 · Sustained suppression is the signal

Your rolling average drifting well below baseline for two-plus weeks — with no obvious explanation — is what's worth paying attention to. Look at sleep, alcohol, training load, life stress. Usually it's one of those.

3 · Listen to your body too

HRV is one signal among many. If you feel terrible but your number is normal, trust how you feel. If your number's low but you crushed a hard session and feel great, that's a normal training response. Subjective indicators still matter.

What To Skip

Catastrophizing single readings. Comparing your number to others. Expensive devices when a chest strap and a free app produce gold-standard data. Daily intensive monitoring when you're not actually changing decisions based on the data. If the tracking is producing more anxiety than insight, the tracking is the problem.