A hamstring does not tear on the day it fails

Monitoring systems keep looking for the session that caused the injury, when the answer is usually spread over the previous month.

The video always shows the same thing. Ninety metres in, the athlete reaches, something goes, and the hand comes down to the back of the thigh. Everyone then goes looking for what was different about that run.

Usually nothing was. The run was ordinary. What had changed was the four weeks in front of it.

Soft tissue does not fail because of one exposure unless the exposure was genuinely extreme. It fails because the tissue's capacity has been drifting down or the demand has been drifting up, and the crossing point happens to land on a Tuesday. This is why single-session monitoring keeps disappointing people. You can measure heart rate, sprint volume, high-speed distance and jump height on the day of an injury and find nothing remarkable, because the day of an injury is a coincidence with a timestamp.

Where telemetry has genuinely helped is in exposing the shape of the preceding block. Two patterns come up again and again. The first is the athlete who has done almost no top-speed running for a month, usually because of illness or exams or a lot of weight room work, and then does a full session at maximum. High-speed running is its own protection; take it away and the tissue detrains for it fast. The second is the athlete who has done plenty of running but whose eccentric strength has been quietly sliding while nobody re-tested it.

Neither pattern is visible from feel, which is the actual case for monitoring. Not prediction. Bookkeeping.

I would go so far as to say that any group not tracking weekly high-speed exposure is guessing, and the guess is systematically biased towards too little, because coaches instinctively protect athletes from the very stimulus that makes them durable. It feels responsible to cut the fast running when someone reports tightness. Sometimes it is. Often it is deferring the injury by a fortnight and making it worse.

There is a caveat I will not pretend away. Even with perfect load data, most of the variance in who gets hurt remains unexplained. Genetics, prior injury, sleep, stress, and plain chance. Anyone selling a system that predicts individual injuries is selling you a correlation that will not survive next season.

So do the unglamorous thing. Count fast metres. Test the hamstring at length every six weeks. Stop asking what went wrong on the day, because the day was innocent.