In a recent clash against the Melbourne Storm, the Brisbane Broncos endured a nightmare rarely seen in professional sport — three players tore their hamstrings in a single game. Two players, Adam Reynolds and Ezra Mam, went down in the same play.

Hamstring strains are the most common non-contact muscle injury in running sports such as rugby league. One in three players will suffer the same injury again.

So why do they happen and what can be done to stop them?

More than 80% of all hamstring injuries in sport occur during sprinting, while others occur during stretching movements such as kicking.

The danger point is usually the “late swing” phase of sprinting: the split second before the foot strikes the ground when the leg is swinging forward at high speed.

At this moment, the hamstrings are contracting while also lengthening.

The hamstrings’ job is to slow the leg and prepare it for ground contact. This requires very high forces at long muscle lengths — a combination that increases vulnerability to injury.

It is not just speed that is dangerous.

Using the recent Storm-Broncos game as an example, when Xavier Coates........

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