The Role of Ankle Plantarflexor Strength and Vertical Stiffness in Acceleration and Maximal Velocity Sprinting

The ankle joint plays an important role in the transmission of force from the body to the ground during sprinting, and the magnitude and duration at which these ground reaction forces can be applied dictates running speed. The aim of this study was to investigate the relationship between the strength of the ankle joint, vertical stiffness and sprint performance. 16 male category one academy football players were required to complete a 40-metre sprint to distinguish acceleration (0-10m) and maximal velocity (30-40m). A controlled frequency hop test was used to determine vertical stiffness, and a novel isometric plantarflexor strength test was used to assess ankle strength. No significant correlation was found between isometric plantarflexor strength or vertical stiffness and any of the sprint variables. A single significant correlation was found between isometric plantarflexor strength and vertical stiffness (r = 0.60, p < 0.05). The results of this study revealed that though isometric plantarflexor strength was significantly related to the stiffness qualities of the lower limb, it did not significantly influence sprint performance for the sample population.