Recovery scores are telling athletes to rest on the wrong days

Morning readiness numbers respond to last night rather than to the training load that actually matters.

A red morning score after an easy Sunday and a green one the day after a brutal session. If you have used any of these apps for a season you have seen both, and the second is the one that should worry you.

The physiology underneath is genuine. Heart rate variability really does track the balance between the two arms of the autonomic nervous system, and hard training really does suppress it. The trouble is everything else that suppresses it. Alcohol, a late meal, a cold room, a bad night with a child, a flight, the first day of a cold you do not know you have yet. All of that lands in the same number, and the number cannot label its own cause.

So an athlete gets a poor score and cuts the session. Sometimes correct. Often the score was reporting a glass of wine, and the session that got cut was the one the whole block was built around. Meanwhile the genuinely dangerous state, the slow accumulation of load across three weeks that ends in a stress fracture, tends to show up in the daily numbers late or not at all, because the body compensates for a surprisingly long time before it stops.

My complaint is not that the data is fake. It is that the resolution is wrong for the decision. Daily readings are noisy and the meaningful signal is a trend across a week or more, but the app puts a colour on the screen every morning and asks the athlete to act on it. Nobody looks at a rolling average when there is a red circle in front of them.

There is a defensible way to use these things, and I would keep it. Track the seven day mean against the month. If it drifts down while training has not changed, or drifts down while sleep looks fine, that is worth a conversation. A single low morning is worth nothing except as one point in that line.

The other use is the one nobody sells, because it is unflattering to the product. The number is excellent at catching illness a day early, which is genuinely useful and has nothing to do with training at all.

Otherwise, ask the athlete how the legs feel walking up the stairs. It is free, it has been available for a century, and in my experience it is the better instrument.