A personal baseline needs more data than one season can give you

Individual reference ranges sound rigorous, but ten monthly readings cannot describe what normal looks like for one athlete.

Everyone has moved to individual baselines, and rightly, because group norms describe a population nobody plays for. The trouble arrives immediately afterwards, in the arithmetic of how many readings a personal normal actually requires.

To say that today is unusual for this athlete, you need to know how much she varies when nothing is wrong. That is a standard deviation, and estimating one from a handful of points is a famously unstable business. With five readings your estimate of her ordinary scatter could easily be half or double the truth. Build a flag at two of those wobbly deviations and you have a threshold sitting wherever the first five Tuesdays happened to land.

Monthly monitoring makes this worse than it looks on paper. Ten readings a season sounds like a series. It is not a series, it is a handful of snapshots taken under conditions that were never the same twice: one after a light week, one in a heatwave, one the morning after a flight. Every one of those contexts changes the reading, so the spread you compute is a mixture of real biological variation and circumstances you did not record. The flag you build from it inherits the whole mess.

There is a temptation to fill the gap by borrowing. Use group variance for the threshold and individual means for the centre. It is a reasonable compromise and it is also a quiet admission that you do not have enough data on the person, which is worth saying out loud rather than burying in a method note.

What I would actually do is cheaper. Measure more often and accept a worse instrument to do it. Twenty rough readings beat six careful ones for the specific job of establishing what normal looks like, because the limiting factor is not the precision of any single measurement, it is the number of them. A weekly hop test on a mat tells you more about an athlete's ordinary range than a quarterly session on a machine that costs as much as a car.

The first year of any individual monitoring programme is not monitoring. It is baseline collection, and pretending otherwise is how squads end up chasing flags in September that mean nothing.

Say that at the start and the programme survives its first false alarm. Say it afterwards and it sounds like an excuse.