There are a lot of theories as to what causes running injury but it seems the answer is fairly obvious;
While I’m sure Ian’s tweet was a tad tongue in cheek he does touch on an important point with running injury – in order to get one you do have to actually run! This is a point that a recent research paper has expanded on,
“Running practice is a necessary cause for RRI [Running Related Injury] and, in fact, the only necessary cause.” Malisoux et al. (2014)
With running being the key risk factor for running injury what other factors influence risk? It seems there’s a disparity between what runners think causes injury and what the research has found;
Runners in this study (Saragiotto et al. 2014) correctly identified excess training as a key factor but also incorrectly blame foot shape (pronation, high arch etc.), wearing the wrong shoes and lack of stretching.
Recent research (Nielsen et al. 2014) found foot pronation was not associated with injury risk. Foot pronation is a normal part of running gait and essential for absorbing some of the load during the impact phase of running. It seems likely that marketing from shoe companies labelling pronation as harmful and providing a solution (in the shape of an expensive shoe) is to blame for this widely held belief. Shoe companies may claim their products reduce injury risk but there is no evidence to date that supports this. It’s a claim more backed by sales than science. (The only study on shoes that I’m aware of to show reduced running injury risk found that using a variety of different running shoes may reduce risk by helping to vary loading patterns Malisoux et al 2013).
For many years runners have been told to stretch to reduce risk of injury and yet a recent systematic review (Lauersen et al. 2013) found no evidence to support stretching either before, or after sport to reduce injury risk. While warming up has shown some evidence of reducing injury risk in some sports, there is little evidence to suggest it significantly reduces risk of running injury. Compression garments, acupuncture and massage have also been suggested to reduce injury risk but again there is no high quality evidence to support this.
Come on then, answer the question! What does cause running injury?
Estimates suggest 60-70% of running injury is due to training error but some papers suggest it may be as much as 80%. Factors that effect how much training load a runner can tolerate before injury will also have a role. There are 2 other key factors that appear to play a part in this – Body Mass Index (BMI > 25) and history of previous injury (Malisoux et al. 2014). A number of studies have now found previous injury, especially in the last 12 months, to play a key role; Saragiotto et al. (2014b) found it to be the main risk factor for running related injury. While high BMI and previous injury may reduce the amount of running your body can manage, strength and conditioning (S&C) is likely to increase it. There is a growing body of evidence supporting the use of S&C to reduce injury risk and improve performance.
Training error and injury risk share a complex relationship (as studied by Nielsen et al. 2012 and discussed in detail here). It may not be that total running mileage on its own is key but how quickly this increases. The old saying of “too much, too soon” is probably fairly accurate.
Closing thoughts: The answers to your running injury woes probably don’t lie in expensive shoes, compression garments or static stretches. Passive treatments like massage and acupuncture are unlikely to change how much training your body can manage. Key injury risk factors are training error, BMI and previous injury. Managing these risks is essential to prevent running injury.