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Running away from clinical heterogeneity
  1. Tom Michie,
  2. Christopher Napier
  1. Department of Biomedical Physiology & Kinesiology, Simon Fraser University Faculty of Science, Burnaby, British Columbia, Canada
  1. Correspondence to Dr Christopher Napier, Department of Biomedical Physiology & Kinesiology, Simon Fraser University Faculty of Science, Burnaby V5A 1S6, British Columbia, Canada; cnapier{at}

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…the injury incidence among runners varies between 11–85% or 2.5 to 38 injuries per 1000 hours of running.1

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 running-related 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.2 For example, having adequate allocation concealment to treatment groups can reduce overestimates in treatment effects.3 However, there is incongruence with the management of clinical heterogeneity.3 Clinical heterogeneity is defined as the variability in participant characteristics, interventions or outcomes.3 In RRI research, this can take the form of differences in runner subpopulations (eg, level of …

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  • Contributors TVM and CN conceived the idea. TVM wrote the first draft. Both TVM and CN revised and approved all subsequent drafts.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Not commissioned; externally peer reviewed.