acute chronic ratio runners

Can We Do Better Than The 10% Rule?

Can We Do Better Than The 10% Rule?

The short answer is yes.

The 10% rule would be familiar to most endurance athletes (limiting increases in training load by no more than 10% per week) and while it’s a good general guide to help us build our mileage, it has some serious flaws.

The 10% rule:

  • doesn’t allow for recovery adaptation weeks

  • isn’t actually supported by evidence

  • doesn’t give much helpful guidance when returning from a period of inactivity from injury or illness

  • may not be an appropriate target at certain times in your training phase

That’s where a broader view can help us plan our training, avoiding large spikes in load that are known to increased the risk of injury.

The acute-to-chronic training ratio compares your mileage for the last week to your average weekly mileage for the last four weeks.

In recent studies with athletes from various sports, injury risk climbs when this ratio exceeds 1.3, and increases significantly when it exceeds 1.5 (see graph below with thanks to Tim Gabbett).


Keeping a regular eye on this ratio (easy if you have the Garmin connect app - see below) can help us find the sweet spot where the right amount of training is improving our performance and importantly staying injury free.


To quote Tim Gabbett, “It’s not the load that breaks you down, it’s the load you’re not prepared for”.

If you’re a numbers sort of person, read more about effective load management strategies at our ‘Creating An Unbreakable Athlete’ series.