A 3-D model was used in this study to determine the influence of midsole hardness, as well as the influence of running in shoes in comparison to barefoot, on the contact forces in the joints of the foot and ankle during running. The results showed that there were no statistical differences in the magnitude and rate of joint loading for changing midsole hardness, nor were there any general trends observed in the measured variables. However, both the magnitude and rate of loading in the subtalar and ankle joints during the impact phase were found to be greater in the barefoot condition than the shod condition. The results suggest that if running injuries are assumed to be related to the impact of heel-strike, running in shoes may aid in preventing injuries, whereas it is still questionable whether changes in the midsole hardness have a general influence on the incidence of impact-related injuries.