Human running on damped surfaces: theoretical strategies for adjusting leg impact mechanics

AbstractA simple spring-mass model can provide insight into human running mechanics and help determine coping mechanisms for changes in running velocity, surface stiffness and surface height. However, previous research assumed that no energy was lost in each step even though most sports surfaces return only a fraction of the energy stored during the first half of impact according to their damping characteristics. When hopping on damped surfaces, humans were found to be more flexed during landing and more extended at take-off compared to undamped surfaces. This study investigated the use of this strategy during running. A spring-mass running model was developed in Matlab and analysed on a surface of fixed stiffness but variable damping. Using a range of running velocities (2 – 6 más-1), leg spring stiffness’ (5 – 50 kNám-1) and retraction angle (50 – 80¼), stable regions for a surface without damping were obtained. Damping was then introduced and the new stable regions and energy losses recorded. Leg spring lengths (and hence centre-of-mass heights) at touchdown were then modified and the extent to which this strategy compensated for the energy losses associated with damping was assessed. These results have provided a theoretical insight into the energetic costs of running on damped surfaces. In future work, these results will be compared to human running to determine how accurately the model reflects human coping strategies