A recent study conducted by researchers at Aarhus University indicates that the most common cause of running injuries is running significantly longer than usual in a single training session. This contradicts the long-held belief that overuse injuries develop gradually over time.

According to Associate Professor Rasmus Ø. Nielsen, part of the research group, running too much in one session compared to one’s usual routine can account for 10-15% of all running injuries. Even a small increase of 1-10% in distance can slightly raise the risk of injury.

The study, involving over 5,000 runners from 87 countries, found no correlation between increased weekly running frequency and injury risk, provided the overall volume isn’t drastically increased. For example, suddenly running ten kilometers every day of the week when previously only running the same distance twice a week can still lead to injuries.

The researchers suggest that runners have been misinformed about the causes of injuries for years. This misinformation stems, in part, from algorithms used in sports watches from companies like Garmin and Apple. These watches may incorrectly flag increased training frequency as a risk factor, even if the total distance remains relatively stable.

Participants in the study reported weekly for a year and a half on any injuries sustained, specifying the day on which the injury occurred. This detailed data allowed researchers to pinpoint the single-session overexertion as a primary cause of running injuries.