What does HRV actually tell me?

The most common mistake is treating HRV as a score to beat. It is not a performance measure and a higher number is not automatically better — it is a rough indicator of where your autonomic nervous system is sitting relative to where it usually sits.

Compare it to yourself, over days. A rolling baseline and a meaningful departure from it is the only reading that supports a decision.

Resting heart rate is a reasonable substitute. If HRV is not available or looks noisy, a resting heart rate several beats above your own baseline carries similar information and is more stable.

Know the limits. The evidence on how much a change in either measure can actually tell you about training status is the reason Train Smart nudges the day rather than rewriting the week.

In Train Smart these adjust the day's working sets rather than issuing a verdict — the readings inform the prescription, they do not replace it.