Two kinds of load land on two different tissues

Distance covered and collisions absorbed stress entirely different structures, so adding them into a single training figure hides both.

A back rower and a winger can finish a rugby match having done comparable amounts of work by almost any summary you care to build, and their bodies will have experienced two unrelated events. One accelerated, decelerated and reached high speeds repeatedly. The other was struck, and struck things, dozens of times while barely running.

The tissues involved do not overlap much. High speed running loads the hamstring in a lengthened position at enormous force, loads the Achilles and the plantar structures on every stride, and drives bone stress through repeated impact along the tibia. Collision loads the shoulder girdle through impact with a planted arm, compresses the neck, bruises muscle directly, and delivers rotational forces to the knee and ankle when a foot is fixed and somebody arrives from the side.

Recovery timelines differ too. Muscle damage from eccentric running work follows the pattern everybody knows, sore for two days and largely resolved by four. Contusion is a different injury, with bleeding into the muscle, and it can restrict range for a week while feeling deceptively minor on day one. Repeated head and neck loading has a timeline nobody can measure at all from the outside.

Which is why I have limited patience for a single number representing a week's work. It is not that the number is inaccurate. It is that it answers a question no tissue asked. A hamstring cares about how many metres were run above roughly eighty five percent of top speed and about nothing else in the file. A shoulder cares about tackle count. Adding those together produces a figure that describes a squad and not a person.

The mechanism argument extends to positions within the same sport. A goalkeeper's landing volume, a fast bowler's front foot impact, a catcher's time in a deep squat. These are load histories that share no structures with the running total sitting next to them in the same column.

Two athletes with identical totals need different weeks, and the reason is anatomical rather than administrative.

If you want to know what will break, ask what the tissue was doing, not how much the body did.