‘Comfort filter’ may reduce injury risk
By Jordana Bieze Foster
Runners today aren’t like the runners of the 1970s. They’re far less likely to be male, thin, or dedicated to the sport. And yet, the medical literature suggests that running injury rates are essentially unchanged.
How much of this can be attributed to footwear design? Longtime biomechanist Benno Nigg, Drscnat, Drhcmult, who gave a keynote on the topic at the IOC conference in Monaco, isn’t sure.
“The effects of shoes on running and running injuries are not well understood,” said Nigg, a professor of biomechanics and co-director of the Human Performance Laboratory at the University of Calgary in Alberta, Canada, who is set to retire at the end of this summer.
The one footwear characteristic Nigg does believe affects injury risk in runners is comfort. This is based on the findings of a 2001 study in which his group found that injury rates in military personnel were significantly lower in those who wore inserts they selected based solely on comfort than in those who wore no inserts. The selected inserts varied widely with regard to component materials.
“We all have different optimal shoes, but we all also have a comfort filter, and that reduces injury risk,” Nigg said. “That’s why running injuries haven’t changed—because you always run in shoes that you like.”
Several studies presented at the IOC conference tend to support the theory that specific footwear design characteristics do not influence injury rates.
In 247 runners randomized to use a shoe with a hard midsole or one with a soft midsole for five months, researchers from the Public Research Centre for Health in Luxembourg found that the risk of running-related injury was similar between groups.
And in a study of 1696 novice runners, investigators from the University of Groningen in the Netherlands found that the incidence of running-related injuries over six weeks was not significantly related to the age of running shoes worn.
In a third study, the Luxembourg researchers found that nine-month follow-up data confirmed earlier five-month results, suggesting that runners who switched between different pairs of shoes had a lower risk of running-related injury than those who predominantly used only one pair of shoes. The nine-month hazard ratio for multiple shoe use was .539, even lower than the hazard ratio of .614 seen at five months (see “Switch trials: Shoe use, striking affect risk in runners”).
Multiple-shoe users were about three times more likely to switch between different brands of shoes than between different models of the same brand or different versions of the same model—which again appears to support the idea that particular shoe characteristics do not influence injury risk. Rather, it may be that sticking with any type of shoe for too long, regardless of its structural features, is detrimental, said Laurent Malisoux, PhD, a researcher at the Luxembourg center’s Sports Medicine Research Laboratory, who presented the findings in Monaco.
“We cannot conclude from our findings any causal relationship, but I think that multiple shoe use is protective against injury,” Malisoux said. “It could induce a variation in external or internal forces, and we know that overuse injury is caused by repetitive microtrauma.”
Mundermann A, Stefanyshyn DJ, Nigg BM. Relationship between footwear comfort of shoe inserts and anthropometric and sensory factors. Med Sci Sports Exerc 2001;33(11):1939-1945.
Theisen D, Malisoux L, Delattre N, et al. Does running shoe midsole hardness influence running-related injuries? Results from a double blind randomized controlled trial. Br J Sports Med 2014;48(7):664.
Kluitenberg B, van der Worp H. Risk factors for running related injuries in novice runners participating in a 6-week running program. Br J Sports Med 2014;48(7): 620-621.
Malisoux L, Urhausen A, Theisen D. Impact of training characteristics on running-related injuries in recreational runners. Br J Sports Med 2014;48(7):631-632.
Malisoux L, Ramesh J, Mann R, et al. Can parallel use of different running shoes decrease running-related injury risk? Scand J Med Sci Sports 2013 Nov 28. [Epub ahead of print]