Dear Editor:
Our research group is currently conducting a systematic review and meta-analysis to, among other things, estimate the total injury incidence rate per 1000 hours of CrossFit training. In this process we have located the retrospective survey paper by Aune and Powers.1
The authors reported an injury incidence of 2.71 injuries per 1000 hours of exposure (2.87 and 2.62 for women and men, respectively). As I tried to replicate the results, I found that the injury incidence were only similar on the decimals.
Among others, a methodological paper by Phillips4,5(p674) has suggested to calculate and express the incidence rate (IR) per 1000 hours as:
To calculate the total incidence rate per 1000 hours of exposure using the results from Aune and Powers,1 the calculation would look like this:
The reported and calculated injury incidence rates per 1000 hours of exposure are presented in Table 1. It seems that Aune and Powers have added 1.00 to the injury incidence. Consequently, I have been able to replicate the findings of other studies using the above-stated methodology.2,3 Hence, it seems that Aune and Powers have made a systematic calculation error. I suggest that Aune and Powers recalculate their injury incidence and provide an update of the paper.
Table 1.
Calculations based on the formula by Phillips4
| Group | Reported Injuries, n | Reported Participants, n | Reported Mean Hours of Exposure | Reported Injury Incidence per 1000 Hours of Exposure | Calculated Injury Incidence per 1000 Hours of Exposure |
|---|---|---|---|---|---|
| Total | 85 | 247 | 200.6 | 2.71 | 1.72 |
| Men | 52 | 142 | 225.4 | 2.62 | 1.62 |
| Women | 33 | 105 | 167.4 | 2.87 | 1.88 |
—Rasmus Tolstrup Larsen, PT, MSc
CopenRehab, Section of Social Medicine, Department of Public Health,
University of Copenhagen, Copenhagen, Denmark
References
- 1. Aune KT, Powers JM. Injuries in an extreme conditioning program. Sports Health. 2017;9:52-58. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 2. Hak PT, Hodzovic E, Hickey B. The nature and prevalence of injury during CrossFit training [published online November 22, 2013]. J Strength Cond Res. doi: 10.1519/JSC.0000000000000318. [DOI] [PubMed] [Google Scholar]
- 3. Montalvo AM, Shaefer H, Rodriguez B, Li T, Epnere K, Myer GD. Retrospective injury epidemiology and risk factors for injury in CrossFit. J Sports Sci Med. 2017;16:53-59. [PMC free article] [PubMed] [Google Scholar]
- 4. Phillips LH. Sports injury incidence. Br J Sports Med. 2000;34:133-136. [DOI] [PMC free article] [PubMed] [Google Scholar]
- 5. Portney LG, Watkins MP. Foundations of Clinical Research: Applications to Practice. 3rd ed. Harlow, England: Pearson; 2014. [Google Scholar]