Fast walking fatigues the ankle dorsiflexors as well as the plantarflexors

Walking at high speeds for longer periods feels uncomfortable and is fatiguing. This study compares ankle flexor and extensor strength prior to and following 35 or 47 min fast walking. Following the walking period, isometric maximal ankle dorsiflexor and plantarflexor strength was reduced with 25% and 10% respectively. Functional strength was also tested: eccentric ankle dorsiflexor strength, necessary to slow down the plantarflexion motion following heel contact, and concentric plantarflexor strength, generating propulsion at the end of stance, also decreased substantially. These results indicate that the feeling of discomfort and fatigue arise due to a decrease in strength of the ankle dorsiflexors and plantarflexors as these muscle groups were already working at a high percentage of their maximal strength when walking at high speeds.