Training science
A systematic review set subjective wellbeing checks against heart-rate variability, resting heart rate and biochemical markers, to see which one actually tracked how athletes were responding to training. The chest strap lost.
Ten seconds. That is how long it takes to answer three questions — sleep, mental energy, soreness — and it is also, according to the best evidence available, a better predictor of how your session will go today than a five-minute HRV reading taken first thing in a quiet room.
That sentence sounds like marketing. It is not. It is the finding of a systematic review that most people building "readiness" products have either not read or have chosen to ignore, because it is inconvenient: it says the cheap method beats the expensive one.
Heart-rate variability has a genuine appeal. It is a number, not an opinion. It is captured by a sensor, not typed in by someone who might be having a bad day and wants to feel justified in skipping the gym. HRV reflects the balance between the sympathetic and parasympathetic nervous system — in theory, a direct read of how recovered the body is, immune to mood and motivation.
That is the pitch behind every recovery ring and chest strap on the market. It is also, on its own, an incomplete picture of what "recovered" means for an athlete about to train.
In 2016, Saw, Main and Gastin published a systematic review in the British Journal of Sports Medicine asking exactly this question: across the published literature on monitoring athletes' response to training, which measures actually moved in step with training load — subjective ones, or objective ones?
Their conclusion was unambiguous. Subjective self-report measures — perceived wellbeing, mood, fatigue, soreness, perceived recovery — were consistently more sensitive to changes in training load than the objective measures commonly used alongside them, HRV included. The objective markers were noisier, slower to respond, and less consistent across studies. The subjective ones tracked training stress reliably, session after session.
The number athletes report about themselves has, in the published evidence, beaten the number a sensor reports about them. Not narrowly. Consistently.
This is not an argument that HRV is meaningless. It is an argument that it is answering a narrower question than people think, and answering it noisily.
A morning HRV reading is sensitive to posture, hydration, room temperature, caffeine, what time you woke up and how you were breathing during the sixty seconds it measured. Day-to-day measurement noise in HRV is often larger than the change a single hard session actually produces — which means the number can move for reasons that have nothing to do with training at all.
It also only sees one system. It does not know that your shoulder has been niggling since Tuesday, that you slept six broken hours because of a flight, or that you are carrying stress from something that has nothing to do with training. Your own nervous system already weighs all of that. A subjective check-in asks it directly. A chest strap asks one narrow physiological proxy and hopes it correlates.
This is the reasoning behind the check-in Forta runs every morning: three questions, ten seconds, no hardware required. That score then decides which side of the exercise ledger the day's session is built from — the same ledger covered in the last two articles on this blog.
On a good-score morning, the session can reach into the expensive side of that ledger. On a bad one, it stays in the cheap side — not because a sensor detected fatigue, but because the athlete reported it, which the evidence says is the more reliable signal in the first place.
None of this means self-report is perfect. It can be gamed, and an athlete who always answers "fine" gets a system that always tells them to train hard. The review's finding is comparative, not absolute: subjective measures outperformed the objective measures commonly used alongside them, not that they are flawless in isolation. The honest answer to a short, direct question remains the best tool actually validated for this job — better than the alternative most apps reach for first.
Ten seconds, three questions, no wearable. The score decides how far into the expensive side of the ledger today's session is allowed to go.
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