The metrics behind Kelesto

What does Recovery represent?

Recovery is Kelesto’s estimate of how ready your body may be for physical and mental demands today. It is not a single sensor reading. Instead, it brings together several signals that Apple Watch and Apple Health already record, such as overnight heart rate variability, resting heart rate, sleep and the training you have done recently, and compares each of them with your own usual range. The result is a readiness interpretation: a way of summarising whether today’s pattern looks similar to your normal days or noticeably different from them.

It helps to think of Recovery as a question rather than a verdict: given how your body has been behaving, how much capacity might you have today? That framing is useful for planning training, choosing between a hard or an easy session, or noticing when several days in a row look below your usual. It is important to be clear about what it is. Recovery is a Kelesto wellness interpretation built on established physiological signals; the composite score itself has not been clinically validated, and it is not a medical measurement of health, fatigue or illness.

Why do these signals contribute?

Heart rate variability describes small changes in the time between heartbeats. Research summarised by Shaffer and Ginsberg links HRV to how the autonomic nervous system balances activity and rest, so a shift away from your usual range can be associated with training stress, short sleep, alcohol or illness. Resting heart rate adds a second, simpler view of the same system: when the body is working harder to recover, resting heart rate often sits a little above its normal level. Because both signals are noisy on their own, reading them together gives more confidence than either one alone.

Sleep provides the overnight context. A short, late or broken night can help explain why cardiac signals look different the following morning, and sleep is also when many of those signals are measured most consistently. Recent training load adds the demand side of the picture. A lower morning after a hard session is often an expected response rather than a warning, and knowing that load was high helps distinguish a normal training response from an unexplained change. Kelesto’s weighting of these inputs is its own interpretation; the research explains why each signal is relevant, not how the score is calculated.

Related researchShaffer & Ginsberg (2017), HRV metrics and norms (opens in a new tab)American Heart Association: All About Heart Rate (opens in a new tab)

How should you use the pattern?

Recovery is most informative across days and weeks. One lower morning is common and often has an obvious reason, such as a demanding workout, a late night or travel. A run of several lower mornings, especially when HRV stays below your usual range and resting heart rate stays above it, is a stronger pattern and may be a sensible prompt to ease training, prioritise sleep or simply pay closer attention to how you feel. Equally, a steady or improving trend during a heavy training block suggests your routine is being absorbed well.

When a reading surprises you, open the connected metrics: HRV, Resting Heart Rate, Sleep and Load usually show which input moved. Your own sense of energy, soreness and mood is just as important and should carry real weight in your decisions. Recovery cannot tell you why a change happened, cannot detect or rule out illness, and should never replace advice from a doctor or coach. Use it as one input for planning, not as permission to ignore how you feel or as a reason to worry about a single number.