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No More Than 10% Rule

How much running is too much? Identifying high-risk running sessions in a 5200-person cohort study

Jesper Schuster Brandt Frandsen, Adam Hulme, Erik Thorlund Parner, Merete Møller, Ida Lindman, Josefin Abrahamson, Nina Sjørup Simonsen, Julie Sandell Jacobsen, Daniel Ramskov, Sebastian Skejø, Laurent Malisoux , Michael Lejbach Bertelsen, Rasmus Oestergaard Nielsen

British Journal of Sports Medicine 2025 DOI: 10.1136/bjsports-2024-109380

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There is a rule not to increase the mileage of a single session by more than 10% compared to your previous longest session. No one knows why it is exactly 10% and who was the first who “invented” this rule, but many coaches follow it. For all runners, of course, it’s a must to stay healthy and not get injured, so it’s highly important to know the borderlines you can’t cross.


In this article, a group of researchers decided to check this rule. More than 5,200 well-trained runners were analyzed. The goal was to analyze spikes in single sessions and overall weekly mileage and to see if they increase the risk of injuries, and to what extent.


1️⃣ Bypassing the 10% mark increased the risk of injury by 1.64 times (when we speak about injuries, it’s a significant number)


2️⃣ No strong relations were found for weekly spikes


Yes, the researchers checked only mileage without looking into intensity, recovery, and other details. But the number of athletes analyzed makes the conclusions more or less accurate.


So, the rule stays in power: no more than 10% more to your longest long run in a while (within 30 days).


Stay safe

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References

1. Jesper Schuster Brandt Frandsen, Adam Hulme, Erik Thorlund Parner, Merete Møller, Ida Lindman, Josefin Abrahamson, Nina Sjørup Simonsen, Julie Sandell Jacobsen, Daniel Ramskov, Sebastian Skejø, Laurent Malisoux , Michael Lejbach Bertelsen, Rasmus Oestergaard Nielsen. How much running is too much? Identifying high-risk running sessions in a 5200-person cohort study. British Journal of Sports Medicine. 2025. doi: 10.1136/bjsports-2024-109380

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