Large prospective studies in military populations are a rich source of good data and information. The only problem with these types of studies are if the nature of the population is applicable and comparable to other populations that you might want to apply the results to. For my purposes here, are those in “the military” the same as “runners”. It will depend on the nature of the research question. A lot of being able to generalize research results from a military population to a running population will depend on the nature of what the military populations do (especially with things like, for example, load carriage; and the asymmetrical gait from rifle carriage), but from the study we did a number of years ago on a naval group undergoing their basic training, they do do a lot of running in running shoes. Unfortunately, accepting the applicability the results from one population to another population can be underpinned by preconceived biases as to if your world view likes the results of the research or not!
In that context, this study on stress fractures caught my eye:
Landing Error Scoring System (LESS) Items are Associated with the Incidence Rate of Lower Extremity Stress Fracture
Kenneth L. Cameron, Karen Y. Peck, Brett D. Owens, Steven J. Svoboda, Lindsay J. DiStefano, Stephen W. Marshall, Sarah de la Motte,
Anthony I. Beutler, Darin A. Padua, et al
Orthopaedic Journal of Sports Medicine July 2014 3:
Objectives: Lower-extremity stress fracture injuries are a major cause of morbidity in physically active populations. The ability to efficiently screen for modifiable risk factors associated with injury is critical in developing and implementing effective injury prevention programs. The purpose of this study was to determine if baseline Landing Error Scoring System (LESS) scores were associated with the incidence rate of lower-extremity stress fracture during four years of follow-up.
Methods: To accomplish this objective we conducted a prospective cohort study at a US Service Academy. A total of 1772 eligible subjects with complete baseline data and no history of lower-extremity stress fracture were included in this study. At baseline we conducted motion analysis during a jump landing task using the LESS. Incident lower-extremity stress fracture cases were identified during the four year follow-up period using the injury surveillance systems at our institution. The primary outcome of interest was the incidence rate of lower-extremity stress fracture during follow-up. The electronic medical records of each potential incident case were reviewed and case status was determined by an adjudication committee consisting of two sports medicine fellowship-trained orthopaedic surgeons who were blinded to baseline LESS data. The association between baseline LESS scores and the incidence rate of lower-extremity stress fracture was examined for total LESS score and for each individual LESS item. Univariate and multivariable Poisson regression models were used to estimate the association between baseline LESS scores and the incidence rate of lower-extremity stress fracture during follow-up.
Results: During the follow-up period, 94 incident lower-extremity stress fractures were documented in the study cohort and the cumulative incidence of stress fracture was 5.3% (95%CI: 4.3%, 6.5%). In univariate analyses total LESS score at baseline was associated with the incidence rate of lower-extremity stress fracture during follow-up. For every additional movement error documented at baseline there was a 15% increase in the incidence rate of lower-extremity stress fracture during follow-up (IRR=1.15; 95%CI: 1.02, 1.31, p=0.025). Based on univariate analyses, several individual LESS items at baseline were also associated with the incidence rate of stress fracture during follow-up. Ankle flexion at initial contact (p=0.055), stance width at initial contact (p=0.026), asymmetrical landing at initial contact (p=0.003), trunk flexion at initial contact (p=0.036), and overall impression (p=0.021) were significantly associated with the incidence rate of stress fracture. In multivariable analyses controlling for sex and year of entry into the cohort, subjects who consistently landed flat-footed or heel-to-toe were 2.33 times (IRR=2.33; 95%CI: 1.36, 3.97, p=0.002) more likely to sustain a lower-extremity stress fracture during follow-up. Similarly, subjects who consistently demonstrated asymmetric landing at initial contact were 2.53 times (IRR=2.53; 95%CI: 1.34, 4.74, p=0.004) more likely to sustain a stress fracture during follow-up.
Conclusion: These data suggest that specific LESS items may be predictive of lower-extremity stress fracture risk and may be helpful in injury screening and prevention.
There is no more information available on this study at this stage than what is in the abstract as it was from the American Orthopaedic Society for Sports Medicine meeting, but this is a pretty awesome study: 1772 participants followed prospectively for 4 years – they don’t get much better than that! Nothing in the methods and analysis that I can see from the abstract is problematic.
The only problem I had, was that I had never heard of the ‘Landing Error Scoring System’, so had to Google it. Turns out it is a test in which the athlete jumps forward from a standard plyometric box (30 cm) and then after landing on both feet, they then jump vertically for maximal height. A score is given to the presence or absence of a number of attributes and measurement angles. More specific information on this test can be read here. What the above study found was that the more “errors” that this test found, the more likely a stress fracture was to develop.
Stress fracture (and all other injuries) cost the military a lot. This test appears as though it can be useful to predict those who are at greater risk, so strategies could be implemented to moderate that risk. Can it identify runners at risk for a stress fracture? We don’t know, but I can see no reason why it might not.
As always, I go where the evidence takes me until convinced otherwise and this study suggests we have another tool to that can be potentially used to reduce the risk for stress fractures.