How to use HRV to guide training blocks

Key points

• Use morning LnRMSSD, read as a 7-day rolling average, not single daily values.
• Compare it with the athlete's own normal range, built from the previous 30 to 60 days. Never compare athletes with each other.
• A drop below the range after a hard block is often expected. An unexplained drop, or one that persists with rising resting heart rate, is the signal to act.
• Stable within the range is the goal. Higher is not automatically better.

What to measure

Heart rate variability (HRV) is the beat-to-beat variation in heart rate. In training, the most useful measure is RMSSD, usually log-transformed to LnRMSSD so day-to-day changes are easier to compare. It mainly reflects parasympathetic (vagal) activity at rest.

Measure it the same way every morning: on waking, before coffee, in the same position. A chest strap or a validated app both work. Consistency matters more than the device.

Daily measurement is ideal. Research groups have shown that three to five measurements a week can still describe the weekly trend (Plews, Laursen, Le Meur and colleagues, 2014).

Build a personal normal range

A single HRV number means little. What matters is where it sits relative to that athlete's own history.

1. Collect several weeks of morning readings before interpreting anything.
2. Take the mean and standard deviation of LnRMSSD over the past 30 to 60 days.
3. Set the normal range as the mean plus or minus a fraction of the standard deviation. Research protocols have used 0.5 SD (Vesterinen and colleagues, 2016); wider bands of about 1 SD reduce false alarms.
4. Track the 7-day rolling average against that range.

Act only when the 7-day average leaves the range, not when one day dips.

Read it with context

The same drop means different things in different weeks.

• After a hard block or race: a dip below the range is expected and usually recovers within days.
• In a taper: HRV often moves around as load falls. That alone is not a warning.
• With no hard training and no obvious cause: look for illness, poor sleep, alcohol, travel or life stress.
• Persisting while resting heart rate rises: the clearest sign that load is outrunning recovery.

Look at three things together: the HRV trend, the resting heart rate trend, and how much HRV varies day to day (the coefficient of variation). When all three point the same way, the signal is real.

Turn it into training decisions

The earliest HRV-guided study, Kiviniemi and colleagues (2007), cut intensity on days HRV fell and found better endurance gains than a fixed plan. Later work moved to rolling averages and normal ranges, including studies in recreational runners (Vesterinen and colleagues, 2016) and cyclists (Javaloyes and colleagues).

A practical version for a coach:

• Inside the range: continue the planned block.
• Below the range and expected (heavy week, race): continue or move into the planned recovery, then check it rebounds.
• Below the range and unexplained, or for several days: replace intensity with easy aerobic work or rest until the trend returns.

Athletes also differ in what suppresses their HRV. For some it is high intensity; for others it is volume. Learning which lever moves each athlete lets you plan blocks around it.

How Endurance Signals applies this

Endurance Signals builds each athlete's normal range from their own history, classifies whether intensity or volume drives their HRV, and recommends whether the next block should push or consolidate. Race weeks are never moved. The terms used here are defined in the Endurance Signals glossary.

Common questions

What is a good HRV score?

There is no universal good score. HRV varies widely between people. What matters is whether an athlete's own 7-day average sits inside their personal normal range.

Should I train hard when HRV is high?

A reading above the range often means the athlete has recovered and can take a hard session, but very high values with a rising resting heart rate can also follow heavy training. Read it with context.

How long before HRV is useful?

Collect several weeks of consistent morning readings before using HRV to change training.

Which HRV measure should athletes use?

Morning LnRMSSD, averaged over seven days, is the standard measure in endurance training research.

References: Kiviniemi et al. 2007; Plews, Laursen, Le Meur et al. 2014; Vesterinen et al. 2016; Javaloyes et al. (cycling). Summarised in Heart Rate Variability: Science and Strategies for Peak Performance, chapters 5 and 6.