I have blogged before (Just How Significant are Heel Impacts at Causing Injury When Running?) and repeatedly commented that the evidence that links impact related factors to running injuries is far from compelling. I am not saying they don’t, it is just that the evidence supporting the link is not strong (and one study has even showed that there are less injuries in those with higher impacts). Since my previous post on this topic probably a day does not go by in which I read somewhere about impacts and injury and about the emphasis on reducing impact related factors in order to reduce injury. Why?
Since I addressed this topic back in 2013, its time for an update and please read the previous post to put this one into context so I do not have to re-litigate some of the same issues. Since I wrote that, there has been another systematic review and meta-analysis on the topic and two very recent studies (there have been others, but they are factored into that systematic review and the two recent ones came since that review was published, so I won’t discuss them).
The systematic review and meta-analysis by van der Worp et al in the BJSM reported that:
The loading rate was higher in studies that included patients with a history of stress fractures and patients with all injury types, both compared with controls. Only studies that included patients with a history of symptoms at the time of kinetic data collection showed higher loading rates overall in cases than in controls. There were no differences between injured subjects and controls for the active and passive peaks of the VGRF.
This pretty much confirms what I concluded previously. The evidence of the link between injury and impact related factors is either just not there or far from compelling (except for tibial stress fractures, which is far from being a common running injury).
The recent study by which was not included in the above review is by Davis et al, also in the BJSM (I did mention this one in my previous post, but back then all we had was the conference abstract and not the full paper which has now been published). This was a prospective study of 249 female runners and found that all impact-related variables were higher in those with medically diagnosed injuries. The only issue I have is how many non-medically diagnosed injuries where there and if they were included is there still a relationship? I have no evidence, but I get the impression that at least half of all running injuries are never medically diagnosed and are self managed. Regardless, this study does appear to come down on the side of the ledger that impact related factors are associated with running injury.
The other recent study by Kuhman et al which was not included in the above systematic review was also a prospective study, including only 19 runners. They collected a number of parameters including peak loading rate of the vertical ground reaction force. On that parameter there was no difference between the 10 that got and injury and the 9 that did not. This study does appear to come down on the side of the ledger that impact related factors are not associated with running injury.
So we not really any further ahead. Some studies show a link (especially for tibial stress fractures) and other studies show no link. My interpretation is that there is either just a weak link or the evidence of a link is far from compelling (in other words, nothing has changed since the 2013 post).
As always, I go where the evidence takes me until convinced otherwise …. and I am still not convinced that impact related factors are an important issue in running injuries except for tibial stress fractures.
van der Worp, H., Vrielink, J., & Bredeweg, S. (2016). Do runners who suffer injuries have higher vertical ground reaction forces than those who remain injury-free? A systematic review and meta-analysis British Journal of Sports Medicine DOI: 10.1136/bjsports-2015-094924