The concept goes something like this: if there is a subtle step-to-step differences in the way we run, then the tissues are loaded very slightly differently with each step. Theoretically, this is a good thing and is a potential way that the body responds to not overload any one part of the tissues too much which should equate to protection from injury. I think my first exposure to the concept was Joe Hamil’s work back in 1999. I recall the concept making a lot of sense to me and a couple of studies back then did show that there was less variability in the gait of those with an injury. For some reason, the concept never seemed to get a lot of traction despite every few or so years a publication on it appearing. Now we have this new study on the concept:
FLUCTUATIONS IN STRIKE INDEX AND SPATIOTEMPORAL PARAMETERS IN PREVIOUSLY INJURED VS UNINJURED RUNNERS
R Mann, K Meijer, L Malisoux, R Brunner, A Urhausen, C Nuehrenboerger, D Theisen
Br J Sports Med 2014;48:632-633 doi:10.1136/bjsports-2014-093494.196
Abstracts from the IOC World Conference on Prevention of Injury & Illness in Sport, Monaco 2014
Background: Long-range correlations in running stride interval have been proposed as an indicator of running-related injury (RRI) and found to change with running speed. They have not yet been used to distinguish running style between runners having previously sustained a RRI or not.
Objectives: To compare long-range correlations and stride-to-stride variability of strike index (SI) and spatiotemporal parameters in previously injured and uninjured runners over various running speeds. We hypothesized significant effects of groups and running speed for these parameters.
Design: Retrospective, case-control study.
Setting: Recreational runners.
Participants: 69 regular male and female runners (currently asymptomatic) either having sustained a RRI during the previous year (n=26) or not (n=43).
Risk factor assessment: Five 2-minute incremental running intervals were performed at 80, 90, 100, 110 and 120% of the individual typical running speed on a treadmill. SI, contact time (CT), flight time (FT), stride time (ST), duty factor (CT/ST), stride length (SL) and frequency were measured using an insole-based system. Coefficient of variance (CV) and the scaling exponent α of the detrended fluctuation analysis were calculated, and effects were analysed using repeated measures analyses of variance.
Main outcome measurements: RRI, defined as a pain or complaint to the lower limbs, progressive in nature and influencing running activity for >1 week.
Results: The RRI group displayed lower CV than the controls for CT (P=.01) and FT (P=.027). Significant differences in α between normalised speeds were found for all variables (P<.048) except SL. CV differed significantly between normalised speeds for ST and SL. No significant interactions were found.
Conclusions: Previously uninjured runners display significantly greater CV in CT and FT. Long-range correlations of SI and spatiotemporal parameters change according to running speed, but are not significantly different between previously injured and uninjured runners. Further prospective study to confirm these findings is warranted.
Firstly, I have no more information on this study than what is in the above abstract as it was a conference presentation. I assume more details will be available in due course when the paper is published in full. So, without getting into any detail on the parameters that they measured and the analysis, they appear to have pretty much showed that the injured group had less variability than the uninjured group. This implies that those with less variability are consistently loading the same part of the tissue more with each step and making them more prone to injury than the uninjured group who with their increased variability spread the load around the tissues more.
This study adds to the body of knowledge on variability or fluctuation of gait as being protective for injury. There are still plenty of unanswered questions; for example: The above was a retrospective study, so we don’t know if variability (or lack of it) is predictive of injury in a prospective study? Can variability be taught? Are there some interventions that can increase or decrease variability?
As always: I go where the evidence takes me until convinced otherwise.
Mann, R., Meijer, K., Malisoux, L., Brunner, R., Urhausen, A., Nuehrenboerger, C., & Theisen, D. (2014). FLUCTUATIONS IN STRIKE INDEX AND SPATIOTEMPORAL PARAMETERS IN PREVIOUSLY INJURED VS UNINJURED RUNNERS British Journal of Sports Medicine, 48 (7), 632-633 DOI: 10.1136/bjsports-2014-093494.196