What HRV actually means for athletes

Your absolute HRV number doesn't matter much. The trend does. Here's how to read it, what makes it drop, and when a low reading really should change your day.

What you're measuring

Heart rate variability is the millisecond-level variation between successive heartbeats. Higher = parasympathetic dominance (rest, recovery). Lower = sympathetic dominance (stress, illness, intense training, alcohol).

Trend, not absolute

A 35 ms HRV is "low" for one athlete and "totally normal" for another. The right baseline is a 28-day rolling personal average. Compare today to your own normal, not to the internet.

Things that drop HRV

• A hard session in the previous 24-48 hours.
• Late-night alcohol (often the biggest single driver in our user data).
• Inadequate sleep duration or fragmented sleep.
• Acute illness — sometimes 24-48 hours before symptoms.
• Travel, jet-lag, dehydration, very large meals close to bed.

Reading your morning HRV

1. Within personal baseline ±10%: normal day, train as planned.
2. 10–20% below: consider easier intensity or shorter session.
3. 20%+ below for 2+ days: back off. This is where overreaching becomes overtraining.
4. Above baseline: "supercompensation" — green light for a hard session.

How Radiant Health uses HRV

The morning briefing reads your HRV trend (Garmin, Oura, Health Connect — whichever has the freshest reading) and folds it with sleep, recent training load and your goal. You don't see "HRV: 35"; you see "your HRV is 18% below your 28-day average — back off the threshold work today and lift instead".