What is HRV, and how do you actually read it?
Heart rate variability is one of the most useful and most misread numbers in health. Here is what it is, and how to read yours without fooling yourself.
What HRV actually is
Your heart does not beat like a metronome. The time between one beat and the next constantly shifts, by milliseconds. Heart rate variability, or HRV, is the measure of that variation.
More variation is generally a good sign. It means your autonomic nervous system, the part that runs recovery and stress without your input, is flexible and able to shift between rest and readiness. Low variation often means your body is under load: hard training, poor sleep, illness, stress or alcohol.
What is a good HRV?
There is no universal good number. HRV depends heavily on age, genetics, fitness and the device measuring it, so comparing your HRV to a friend or a population average tells you almost nothing.
What matters is your own baseline. A reading is high or low relative to your normal range over the last few weeks. A number that is low for you is the signal, not a number that is low compared to a stranger.
What moves your HRV
Sleep is the biggest lever: short or broken nights push HRV down. So do late alcohol, a hard training day, illness coming on, and sustained stress. Consistent sleep timing, easy aerobic work and recovery days tend to lift it over time.
HRV is also noisy day to day. One low morning is not a verdict. A trend of several low mornings, especially alongside a higher resting heart rate, is worth listening to.
How TIDES reads it
TIDES reads HRV against your own baseline, not a stranger's average, and only alongside the rest of you: resting heart rate, sleep, and the load from yesterday. It bends today's plan when several markers agree, and when it does not have enough data yet, it says so instead of inventing a number.
Common questions
What is a good HRV?
There is no universal good HRV. It depends on age, genetics, fitness and the device. What matters is whether a reading is high or low relative to your own baseline over recent weeks.
Why is my HRV low today?
A single low HRV morning is usually explained by short or broken sleep, late alcohol, a hard training day, illness or stress. One low reading is noise; a run of low mornings is a signal.
How can I improve my HRV?
Consistent sleep timing, enough total sleep, easy aerobic training, limiting late alcohol, and real recovery days tend to raise HRV over weeks. It responds to habits, not to a single day.