Hamstrings tear at top speed, not out of the blocks

The drive phase gets blamed for sprint injuries because it looks violent, while the damage almost always happens later in the race.

The mental picture is of an explosive start ripping something. It is a good picture and it is mostly wrong. The hamstring injury in sprinting overwhelmingly happens during the swing phase at high speed, in the fraction of a second before the foot touches down, when the muscle is lengthening while being asked to contract hard to stop the shin whipping forward.

That is a specific and unusual demand. The muscle is being stretched and loaded at the same time, at a length near the end of its range, at a rate that only occurs when an athlete is running close to maximum. Out of the blocks the leg is working through a much shorter range with the hip flexed, the forces are large but the lengths are safe, and the limb is not decelerating anything at speed. That is why the blocks feel brutal and are comparatively benign.

The practical consequence is uncomfortable for coaches, because it means the only way to prepare a hamstring for the injuring situation is to put it in that situation. You cannot inoculate against maximum velocity mechanics with strength work alone, however good the strength work is. The athlete has to run fast, regularly, all year, in controlled doses, so that the tissue is repeatedly exposed to lengths and speeds it will meet in competition.

Which collides with the way most seasons are structured. Athletes do general work in winter, build speed as competition approaches, and then arrive at the point of highest velocity with the least accumulated exposure to it, usually in a meaningful race with adrenaline supplying an extra few per cent. That is the classic first-round pull, and it is a planning failure rather than bad luck.

Eccentric strength work has a real place in this and the evidence for it is better than for almost anything else in the injury prevention library. But it is a supplement to running fast, not a substitute, and I have watched squads treat it as a substitute because it can be done indoors in February when nobody wants to sprint on a cold track.

The cold track is the problem. Not the blocks.

Run fast in the winter or pay for it in the spring.