HRV vs resting heart rate for workout recovery

Most recovery apps show both numbers side by side without explaining why you'd need two. Heart-rate variability (HRV) and resting heart rate (RHR) are related — both reflect activity in your autonomic nervous system — but they behave differently enough that each catches things the other can miss.

What each one measures

• Resting heart rate is simple: beats per minute at rest. Lower is generally associated with better cardiovascular fitness, and a short-term rise above your normal is a common early sign of accumulated fatigue, illness, heat or dehydration.
• Heart-rate variabilitymeasures the tiny differences in time between consecutive heartbeats. It's a more direct window into the balance between your “fight-or-flight” and “rest-and-digest” nervous system branches — higher variability at rest generally reflects a more recovered, less stressed state.

Where they agree, and where they don't

On a day of genuine overreaching, both often move together: resting heart rate ticks up while HRV drops. But they can also diverge — research on athlete monitoring notes that HRV is sensitive to a broad range of stressors beyond training (sleep, hydration, emotional stress), which makes it noisier day-to-day, while resting heart rate tends to be a steadier, slower-moving signal. Neither one is strictly “more accurate” — they're better used together than in isolation.

A practical rule of thumb

• Both normal → business as usual.
• One slightly off, the other normal → probably noise; check how you actually feel before changing anything.
• Both moving the same direction (RHR up, HRV down) for more than a day → a genuine signal worth respecting with an easier session.

Why Fit4i looks at both

This is exactly why Fit4i's readiness score doesn't rely on HRV alone — it weighs HRV and resting heart rate against your own personal baselines for each, together with sleep and recent training load, so a noisy single-metric day doesn't trigger an unnecessary change to your plan.