Small changes in the varus alignment of running shoes allow gradual pronation control

Introduction: Excessive pronation is discussed to be the cause of various overuse injuries in distance running which makes stability features of running shoes a huge research interest. Several authors have shown the reduction of pronation range and velocity induced by shoes with extreme varus angles (VA) of 8-10 degrees. However, a reduction of cushioning properties was also observed in those shoes. Therefore, this study is aimed to investigate if shoes with moderate VA, usable for everyday running, are suited to reduce pronation parameters while maintaining cushioning properties. Methods: In two laboratory studies (n = 11, n = 10) the effects of gradually (1 degrees steps) increasing VA between 0 degrees and 4 degrees were investigated with two different samples of running shoes. Additionally, a field study (n = 17) determined subjects' perception of the different VA conditions. Results and discussion: Linear reductions of pronation excursion (p<0.01) and pronation velocity (p<0.01) were observed with increasing VA between shoes, whereas cushioning parameters remained unaltered. Runners did not perceive changes in shoe properties due to different VA nor did they favour any condition. Conclusion: In running shoe designs, small varus perturbations can be implemented to fine tune the pronation parameters and thereby create the runner specific pronation control.