Hamstrings tear before the foot lands, not after

The most common injury in sprinting happens during the swing phase, which is why so much prevention work aims at the wrong moment.

The athlete grabs the back of the leg and pulls up. Everyone assumes something gave way when the foot hit the track. Almost always, it did not. The damage occurred a fraction earlier, in the air, while the leg was still swinging forward and the hamstring was working hardest to stop it.

Think about what that muscle group does at top speed. The lower leg is being thrown forward at considerable velocity, and something has to decelerate it before the foot comes down, then reverse it so the foot is already sweeping backwards at contact. The hamstring does both, under high load, while lengthening. Lengthening under load is the condition in which muscle tears. Late swing is the peak.

This matters because it changes what prevention should look like. Enormous amounts of gym time go into hamstring strength in shortened positions, curling a weight with the knee bent, which builds a muscle that is strong in a range where it is not being injured. Better work loads the muscle long and eccentric: exercises where the athlete resists the leg extending, or holds tension in a lengthened position under control. Those hurt more and look less impressive and they address the actual moment of failure.

The other half is exposure. A hamstring only learns to survive top-end speed by doing top-end speed, regularly, in small doses, when fresh. Programmes that avoid maximal sprinting to keep athletes safe produce hamstrings that have never met the load they will eventually face, and then the load arrives in a race in April.

Here is where I part company with a chunk of the field. I think the fear of sprinting has caused more hamstring injuries than sprinting has. Teams in field sports especially will do endless preventative circuits and then let a player go from months of controlled running to a full-speed chase after a loose ball. The circuit did not prepare him for that. Nothing prepares him for that except the thing itself.

The rest is boring and true. Fatigue raises the risk, so the last repetition of a hard session is the dangerous one. Previous injury raises the risk more than anything else, so the rehabilitation you rushed in March is the reason for the tear in July.