Researchers themselves call the results a paradigm shift in the way of looking at injuries that come from running. The perception within sports medicine has long been that typical running problems such as knee injuries come after a long period of strain.
But when researchers from, among other places, Aarhus University in Denmark followed over 5,200 runners from 87 countries for 18 months, they saw another common factor. It was when the runners suddenly increased the distance on one occasion that the injuries occurred. If the runners ran between 10 and 30 percent longer than the longest distance the last month, they reported injuries more often. The greater the increase, the higher the risk, and those who increased the distance by 100 percent or more ran a greatly increased risk of injury.
Increase cautiously
Researchers suggest that runners who want to increase the distance should do so cautiously – with less than 10 percent at a time. Rasmus Nielsen, the study's lead author, believes that many "smart" training watches and apps today are based on an algorithm that gives incorrect tips.
The algorithm used today in many apps and smart training watches is called "Acute Chronic Workload Ratio" (ACWR). The algorithm recommends a maximum 20 percent increase to avoid injury. It is based, according to Nielsen, on a study with 28 participants and was developed for people who play team sports.
Incorrect information
This means that millions of runners receive incorrect information from their sports watches every day. They think they are following a scientific method to avoid injuries, but in reality, the algorithm cannot predict anything about injuries at all, he says to the magazine Sci Tech Daily.
Together with colleagues, they are working on an updated algorithm that they hope will be able to flag injury risk more scientifically.
It is not commercial, but it will be made available for free to runners, clinics, and companies that want to use it, says Nielsen.
The study has been published in British Journal of Sports Medicine and the average age of the participants was 46 years.
