The tracker sits between your shoulder blades and the injury happens in your leg

Wearable telemetry infers limb load from a unit strapped to the torso, which is a bigger leap than the dashboards ever admit.

The vest goes on the upper back. The device sits between the shoulder blades, records position and acceleration, and from that we get numbers about what a player's hamstring, groin and knee have endured. Nobody involved in the actual measurement is pretending otherwise, but by the time the figures reach a meeting they have quietly turned into facts about legs.

Some of the inference is sound. Whole body movement really does constrain what the limbs must have done. If the torso travelled thirty metres in four seconds, the legs did something specific and demanding to make that happen. Fine.

The trouble is everything asymmetric. Two players cover identical distances at identical speeds. One of them takes every turn off his left foot because his right knee has a history and his body has quietly written a rule about it. The trunk-mounted unit sees two similar afternoons. The two knees have had completely different afternoons, and the compensating side is the one accumulating load nobody is counting.

That asymmetry is measurable. Force plates, pressure insoles, limb-mounted sensors, all exist and all give a side-by-side picture. They also give data that is fiddly, that varies with surface, and that produces awkward conversations about a player who is technically available. So it tends to live in the medical department rather than the performance report, and the performance report is what the coach reads.

I think this is the widest gap between what clubs claim to know and what they know. The public conversation about load talks about totals, because totals are what the standard kit produces, and totals are exactly the thing that hides an imbalance. You can be perfectly average on every published metric while one leg does sixty per cent of the braking.

None of this is an argument for more gadgets. It is an argument for reading the ones you have honestly. When a fitness report says a player's mechanical load was moderate, the correct mental translation is that his torso had a moderate week. What his left adductor had is a separate question, and the honest answer is often that nobody looked.

The best information in the building is still the physio's hands and the player saying it feels tight.

That is not a fashionable thing to write in a sport busy buying sensors, but it is where the tears actually get caught.