LAUSR

As the Danish proverb goes: ‘It’s difficult to make predictions, especially about the future.’ To the average clinician, it certainly might seem that way when it comes to predicting which runners will get injured. The range of injury incidence cited above—or a slight variation—is a common opener to many studies on runningrelated injuries (RRIs). Given the enormous amount of time dedicated to this body of research, why is it that we can still only cite a range of injury incidence that effectively says that maybe all or maybe a few runners will experience an RRI, essentially rendering this statistic useless? One core issue limiting advancements in RRI research is study heterogeneity. Currently, the Cochrane handbook provides recommendations on managing statistical and methodological heterogeneity. For example, having adequate allocation concealment to treatment groups can reduce overestimates in treatment effects. However, there is incongruence with the management of clinical heterogeneity. Clinical heterogeneity is defined as the variability in participant characteristics, interventions or outcomes. In RRI research, this can take the form of differences in runner subpopulations (eg, level of experience or competitiveness), prescribed interventions (eg, strength training, gait retraining, footwear) or the definition of an RRI (eg, missed training days vs reported pain), among others. The occurrence of high clinical heterogeneity makes comparisons between studies difficult and limits the utility of the results for clinical practice.