Lateral edge friction variability in indoor sports shoes

It has previously been speculated that the occurrence and severity of lateral ankle sprain injuries is linked to excessive shoe-surface friction. The purpose of this study was to assess the amount of lateral edge friction in indoor sports shoes, and evaluate the variation from the traditional forefoot traction test. Therefore, we modified the ISO:12387:2019 test for slip resistance and positioned the shoe on its lateral edge while simulating a sideways movement. All tests were conducted on an indoor surface. In general, we found that lateral edge friction on average was 22% lower than forefoot friction (p<0.0001). However, linear regression showed that the forefoot test could only explain 63% of the variation in edge friction, thereby suggesting that a lateral test is needed to adequately inform on lateral edge friction. Future research is planned to determine whether a noticeable change in friction coefficient is also a ‘valuable change’, hence potentially having clinical implications for injury prevention.