ULTRA SCIENCE
Readiness, resting heart rate and HRV
Combine how you feel with consistent measurements before adjusting a session.
Signals versus a composite score
Resting HR and HRV describe aspects of cardiovascular/autonomic state. They do not measure complete muscle recovery. Evidence for a physiological signal does not validate a proprietary score made from it.
Begin with the decision you actually face: proceed with the planned demanding session, adapt it or postpone it. A readiness record should support that decision rather than become another target to optimize. Separate a raw measure, such as resting heart rate, from the device’s interpretation. Also separate how recovered you feel from whether you have enough time, food and sleep opportunity to execute the session sensibly.
Build your own baseline
Author routine: briefly log sleep, fatigue, soreness, motivation and unusual symptoms before viewing the device score. If measuring HRV, keep device, timing, posture and recording method consistent. Note alcohol, travel, illness and unusual load. Compare repeated observations with your own normal pattern.
Use the same brief questions and response labels each time. For example, describe fatigue relative to your own normal day and record whether soreness changes ordinary movement. Add the previous session’s duration and perceived difficulty. If the sensor did not record reliably, mark the measurement missing. Do not fill gaps with the last value. Review several observations together before deciding that an isolated fluctuation is a pattern.
Validity, reliability and meaningful change
Artefacts and recording conditions affect repeatability. Meaningful change depends on individual variability and measurement error; no universal HRV target applies to everyone. A normal HRV can coexist with soreness and incomplete recovery.
A baseline is specific to the way you measured it. Comparing overnight values with a seated morning recording may mix methods rather than reveal a physiological change. Device changes and algorithm updates deserve a note. Interpret personal trends without comparing your absolute HRV with another runner’s number. A score is not more trustworthy simply because it is shown to several decimal places or uses a reassuring colour.
Make the safer training decision
When several signals worsen, consider replacing a demanding session with easier activity or rest and reassess. A favourable score never overrides illness, chest symptoms, fainting or injury symptoms. Persistent unexplained fatigue deserves professional assessment. Do not diagnose overtraining from one low reading.
Write down the reason for an adjustment and check what happened afterwards. For example, poor sleep plus unusual fatigue and a demanding previous day may justify an easier session even when the watch looks normal. If you feel well but one reading is unusual, inspect recording quality and context before reacting. Do not repeatedly override obvious illness or accumulating symptoms while waiting for a device to agree.
Who, cost and repeat timing
Useful throughout training and after ultras. A short daily log is free; wearables are optional, especially if scores cause anxiety. Repeat regularly enough to establish context, using the same method; more sensors are not automatically more actionable.
Keep monitoring short enough to maintain honestly. If collecting scores increases anxiety or encourages compulsive checking, simplify to a few practical observations or stop using the composite score. Professional input is appropriate when symptoms persist, ordinary function deteriorates or you cannot reconcile the pattern with training. This method is an educational decision aid; it cannot clear someone medically for exercise or determine a return-to-running prescription.
Use this with
Evidence and limits
Evidence: Moderate. Relevant monitoring principles; individual ultra recovery decisions require broader context. Does not validate proprietary readiness scores or diagnose complete recovery.
Version and review
AI-assisted evidence appraisal is not credentialed clinical review. Publication authorization and application release dates are separate from scientific review.
Evidence markers identify statements and their limits; practical examples are not validated individual prescriptions.
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