Alteration in Foot Strike Pattern While Running with Elastic Insoles: Case Study on the Effects of Long-term Training

Motor adaptation is a form of motor learning that involves changes in the control of movements that occur as a consequence of optimization in repeated task exposure or practice. A good example of this can be found in human running. It is thought that humans run in accordance with the presence or absence and shape of shoes. Three foot strike patterns exist in running, classified according to which portion of the sole first connects with the ground: RFS (rear-foot-strike; heel connection), MFS (mid-foot-strike, simultaneous heel and toe connections), and FFS (fore-foot-strike; toe, or ball connection). RFS is often seen in runners wearing shoes, whereas FFS is commonly seen during routine barefoot running. This study examined how humans adapt to assistive footwear (environmental exposure)s throughout approximately one month of running training. We found that the shape and stiffness of a modified insole affected the foot, functioning as a spring during running. As training continued, the subject adapted to the structure of the footwear by altering his foot strike pattern while reducing his heart rate. The foot strike pattern changed from heel contact to contact from the side of the toe or arch, and the pattern of the ground reaction force changed from that of RFS to that of FFS or MFS. These results indicate that the change in foot compliance while landing and during grounding affects the foot strike pattern to improve the efficiency and capability of running through long-term training.