For many years, a hamstring strain was reliably a four to six-week injury.
It rarely took much more or much less than that.
These days it's not uncommon to see one of our favourite AFL stars hobble from the field looking only mildly uncomfortable, only for the club to announce a few days later that they'll miss the next three months.
So, what changed?
The answer isn't that hamstring injuries have become worse.
It's that we've developed a much better understanding of the different types of hamstring injuries, allowing us to tailor recovery times much more accurately.
Every muscle is made up of two main components: the muscle fibres themselves (the red meat) and tendons (the tough white tissue) that attach the muscle to bone.
While a thorough physical examination gives us plenty of clues, MRI has been a game changer in showing us exactly where the injury has occurred.
We can now tell whether the tear is in the muscle fibres, the tendon, or at the point where the muscle and tendon join together.
Over the past two decades, researchers have followed athletes after these different types of injuries.
They found that players with injuries involving the tendon, or the muscle-tendon junction, were far more likely to suffer another hamstring tear if they returned after the traditional four to six weeks.
This was despite the player often feeling strong, confident and ready to play.
Many long-time footy supporters will remember players who seemed to be constantly re-injuring the same hamstring, perhaps leading to an premature retirement.
We now know that tendon injuries are a major reason why.
Tendons have a relatively poor blood supply and heal much more slowly than muscle, often despite not being any more painful.
If they are pushed too hard, too soon, they are much more likely to tear again.
After multiple re-injuries, achieving a full recovery becomes much more difficult.
That's why clubs now take a much more cautious approach.
While it can be frustrating to see a young star sidelined for months with what appears to be "just a hamstring", the extra time is usually an investment in their long-term career.
The aim isn't simply to get them back as quickly as possible, it's to get them back once, and get them back properly.
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