Science & Rest
HRV and Recovery: Why Your Personal Baseline Matters
29 October 2026 · 5 min read
Heart rate variability can help put recovery into context, but there is no single HRV number that tells everyone how ready they are to train. The metric, recording conditions and your own history all matter. HRV metrics and measurement context
A useful starting question is not, “Is my number better than someone else's?” It is, “How does this compare with my usual readings—and how do I feel?”
Clarify's Charge model is designed to bring that context together. It is a wellness estimate, not a measurement of how much energy your body has left.
What HRV actually measures
Heart rate variability describes the differences in time between successive heartbeats. RMSSD is one way to quantify those differences and is commonly used to study parasympathetic modulation of the heart. It is not a complete measurement of the autonomic nervous system. HRV overview
Different HRV metrics and recording durations are not automatically interchangeable. That makes consistent comparisons more useful than mixing numbers from unrelated measurement methods. Measurement considerations
Think of your baseline as a reference point—not a target you need to beat every morning.
What goes into Charge
The Charge model described here assigns five inputs the following starting weights. These percentages are Clarify's calculation settings, not scientifically established shares of human recovery.
| Input | Starting weight | What the model considers |
|---|---|---|
| HRV | 55% | The recorded HRV value relative to your recent pattern |
| Sleeping heart rate | 20% | Your overnight heart-rate pattern relative to baseline |
| Sleep performance | 15% | A calculated sleep score, rather than a separate vital sign |
| Sleeping respiratory rate | 5% | Your recorded breathing rate relative to your usual pattern |
| Skin temperature deviation | 5% | Changes in skin temperature relative to baseline |
Under this model, an unavailable input is omitted and the remaining weights are rescaled proportionally. Missing information is not treated as a normal reading, and a score based on fewer inputs should not be assumed to contain the same information.
Why the baseline changes gradually
The specified model uses an exponentially weighted moving average: recent observations contribute more than older ones. Its baseline centre uses a 14-night half-life, while its estimate of variability uses a 21-night half-life.
Those half-lives describe how quickly older information loses influence. They are not fixed 14-night and 21-night cut-offs, and they are not biological recovery times.
The model also limits extreme observations to within three estimated spread units when updating the reference. This process, called winsorization, limits an unusual observation's influence; it does not establish whether that observation is harmless or meaningful.
These settings describe a smoothing method, not proof that the resulting score predicts performance.
What your score cannot establish
A Charge of 74 should be read as 74 points on Clarify's scale, not “74% recovered.” A high score does not establish that a demanding session is safe, and a lower one does not automatically mean exercise is inappropriate.
Heart-rate measures cannot capture every aspect of fatigue, wellness or performance. Research supports interpreting them alongside training history and subjective information. Training-monitoring review
Before using a score to guide your day, check the underlying readings, your recent workload and how you actually feel. Do not use an encouraging score to dismiss pain or symptoms.
The aim is a better-informed decision—not a perfect number.
General wellness information, not medical advice. Charge is not a diagnosis or medical clearance to exercise.
General wellness information, not medical advice. Talk to a professional about any health concern.