Hamstrings tear at the end of the swing, not during the push

The injury happens while the muscle is lengthening under load before the foot has touched anything.

Most sprinters who pull up mid-race describe it the same way. Something went at the back of the leg while the leg was still in the air.

That detail matters, because it points at the mechanism. Late in the swing phase the shin is travelling forward fast and the hamstring has to decelerate it, contracting hard while being stretched. Eccentric load, at long muscle length, under time pressure. That combination is where tissue fails. It is not the push against the track, even though the push is where the visible effort appears and where most people assume the damage occurs.

Once you accept that, some training conventions look questionable. Curls, done through a short range with a light weight, load the muscle at exactly the length it is least likely to fail at. Athletes do them, feel a burn, and conclude the hamstring is being looked after. The exercises that actually match the failure mode are the awkward ones. Nordic lowers. Single leg deadlifts through a full range with the pelvis controlled. Anything that asks for strength when the muscle is long.

There is a second contributor that gets less attention, which is where the foot lands. A runner who overstrides is asking the hamstring to decelerate the shin over a longer distance and finish the job later, and they are also adding a braking impulse at touchdown. Fatigue makes this worse in the last twenty metres of a two hundred, which is precisely where the injuries cluster. That is not a coincidence and it is not bad luck.

I will concede the honest limit here. Nobody can predict which athlete tears and which does not, and every screening protocol proposed in the last two decades has performed badly at the individual level. Strength at long muscle length reduces incidence across a group. It does not make any particular person safe, and coaches who promise otherwise are selling something.

What it does do is change the odds and shorten the return when something does go, because a muscle that has been trained long recovers its function faster.

The rest is exposure management. Get the athlete used to top speed gradually and regularly rather than in occasional heroic doses, because the leg that tears in April is almost always a leg that had not run properly fast since October.