Also known as: Heart Rate Variability, HRV recovery score
HRV, heart rate variability, is the variation in time between consecutive heartbeats. It reflects the balance of your autonomic nervous system, and runners use it as a day-to-day recovery and readiness signal.
A healthy heart does not beat like a metronome. The gap between beats varies slightly from moment to moment, and that variation is HRV. Higher HRV generally reflects a nervous system leaning parasympathetic, in rest-and-recover mode, rather than sympathetic, in stress-and-go. A reading below your own normal is one signal among several that training stress, poor sleep, illness or life stress has not been recovered from yet.
Most consumer devices sample HRV overnight, or during a short morning reading, through a chest strap or an optical sensor. They report RMSSD, the root mean square of successive differences between heartbeats, which is the most common metric in sports-science HRV research. Devices usually smooth it into a rolling personal baseline rather than compare it against a population norm, because normal HRV varies enormously between individuals.
There is no good HRV number in general. 40ms can be a personal high for one runner and a personal low for another, since HRV tracks age, genetics, fitness and measurement method as much as recovery state. Read the trend against your own rolling baseline. The raw number means little next to anyone else's.
Work on HRV-guided training in endurance athletes, including research by Plews, Laursen and Buchheit, has found that adjusting training on HRV trends can beat a fixed, pre-planned schedule for some athletes: back off after a sustained decline, push when HRV is stable or rising. The benefit shows up most around illness and heavy training blocks, and the effect size varies by study and by athlete.
Reacting to one low morning is the usual overreaction. Day-to-day HRV is noisy, moved by alcohol, poor sleep, travel, even what time you took the reading, so sports-science guidance favors multi-day trends against a rolling baseline over any single number. HRV is also a whole-body stress signal rather than a running-specific one. A low reading may have nothing to do with training load at all.
HRV is too noisy day to day to act on one morning reading, and a hand-kept rolling baseline is the first habit to lapse when the week gets busy.
HRV on its own also does not say what to change in tomorrow's session. It has to be read next to training load.
Vertical tracks your HRV trend alongside your training load automatically. Your coach can use that context to discuss your recovery and adjust your plan with you, rather than reacting to one morning number.
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