Bone does not care about your session plan

Load monitoring in athletics is built around muscle and tendon, and the tissue that most often ends a season adapts on a different clock.

Muscle responds to a hard fortnight in a hard fortnight. Bone does not. It reacts to loading on a timescale of months, remodels slowly, and passes through a window early in that process where it is temporarily weaker than it was before you started.

Which means every load-monitoring system built around acute and chronic ratios is describing the wrong tissue.

Those systems came out of team sports and were tuned for soft tissue, where a sudden spike in high-speed running plausibly explains a strain a few days later. Apply the same logic to a young distance runner and you get a green light on a training block that is quietly accumulating bone stress. The athlete feels fine, because bone injury announces itself late and vaguely, and by the time there is pain that changes with weight-bearing the damage has been developing for weeks.

The variables that matter for bone are also different, and mostly not in the spreadsheet. Total impacts rather than intensity. Surface. Whether the athlete is eating enough to support the remodelling in the first place, which is by some distance the biggest single factor and the one least likely to be discussed. Energy availability sits underneath every stress fracture I have ever seen argued about, and coaches persist in treating those injuries as mechanical accidents.

Here is the uncomfortable version. A programme that produces repeated bone stress injuries in the same training group does not have bad luck and does not have a surface problem. It usually has a nutrition culture problem, and the sport is bad at saying so because saying so is a conversation nobody enjoys.

There is a second, more forgivable failure. Distance runners are often moved between surfaces and shoe types by season, and the change from soft ground in winter to a hard track in spring alters bone loading dramatically at the exact moment training intensity is rising. Two changes at once. Nobody staggers them.

The practical fix is unglamorous and slow, like the tissue. Introduce track volume in weeks rather than days. Count impacts, not just kilometres. Ask about menstrual health and about breakfast, and mean it.

And when an athlete comes back from a bone injury, remember that the healed scan is not the finish line. The remodelling is still going on underneath, and the second fracture is usually the one nobody was watching for.