Researchers of a new study have found evidence that a lower step rate is an important risk factor for bone stress injuries among college cross country runners.
Lower Step Rate Increases Risk of Bone Stress Injury?
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In “Lower step rate is associated with a higher risk of bone stress injuries: a prospective study of collegiate cross country runners,” published online on May 14, 2021 in the British Journal of Sports Medicine, they investigated whether running biomechanics and bone mineral density were independently associated with bone stress injury among National Collegiate Athletic Association Division I cross country runners.
The prospective, observational study collected data from 54 healthy runners that were followed over three consecutive seasons.
The researchers measured whole body kinematics, ground reaction forces and bone mineral density each preseason using motion capture on an instrumented treadmill and by using total body densitometer scans.
In addition, the research team tracked all bone stress injury diagnosis for up to 12 months after the preseason data was documented.
The research team found that step rate, center of mass vertical excursion, peak vertical ground reaction forces and vertical ground reactions forces impulse were all positively correlated with bone stress injury incidence.
After adjusting for history of bone stress injury, a higher step rate remained independently associated with a decreased risk of bone stress injury.
A runner’s bone stress injury risk decreased by 5% (relative risk (RR): 0.95; 95% CI 0.91 to 0.98) with each one step/min increase in step rate.
The bone mineral density z-score was not a statistically significant risk predictor in the final multivariable analysis (RR: 0.93, 95% CI 0.85 to 1.03). None of the other biomechanical variables were found to increase bone stress injury risk, the researchers reported.
“Low step rate is an important risk factor for bone stress injuries among collegiate cross country runners and should be considered when developing comprehensive programs to mitigate bone stress injury risk in distance runners,” they wrote.
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This is a fascinating development. In my practice we've seen similar outcomes with the revised protocol. The key differentiator seems to be patient selection criteria. Has anyone else noticed the correlation with BMI thresholds?
Great point. I'd push back slightly on the conclusion, the sample size in the cited study is too small to draw population-level inferences. That said, the directional signal is compelling and worth a larger RCT.
We implemented a similar approach last year. Early results are promising but we're still gathering 12-month follow-up data. Happy to share our protocol if anyone is interested.
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