Minimalist Running Shoes Increase Intrinsic And Extrinsic Foot Muscle Volume In Habitual Shod Runners

Abstract

Minimalist footwear (MF) running has gained popularity recently partially because it is claimed to strengthen the intrinsic and extrinsic foot muscles. However, there is limited data on the change in muscle size associated with a transition to MF. PURPOSE: To examine the effects of a transition to MF on the intrinsic and extrinsic foot muscle volume. The relationship between participants’ compliance with MF and changes in muscle volume was also evaluated. METHODS: 20 habitual shod runners underwent a 6-month, transition program to MF running, including foot and ankle strengthening and a gradual increase in running in the MF. 18 matched shod runners were instructed in the same strengthening program, but they continued their normal mileage in their traditional running shoes. Runners’ compliance with MF was monitored using an online survey program. We measured intrinsic and extrinsic foot muscle volumes with MRI before and after the program. RESULTS: Weekly mileage between groups was similar at baseline (p=0.216) and after the program (p=0.612). However, runners in the MF group exhibited significantly larger extrinsic (p=0.011) and intrinsic (p=0.001) foot muscles after the program. Intrinsic foot muscle growth was mainly observed at the forefoot (p=0.004) but not the rearfoot region (p=0.104). Muscle volume of runners in the control group remained similar after the program (p=0.333-0.948). A significant positive correlation was found between participants’ compliance with MF and changes in the extrinsic muscle volume (r=0.506; p=0.023). CONCLUSION: Transition to MF running was associated greater extrinsic and intrinsic foot muscle volume. Additionally, the extrinsic muscle growth was correlated with the use of MF.Table 1: Muscle volumes (mm3/kg) before and after transition program in the MF group compared with the control