Measurement of traction forces exerted by the foot in motion*

When walking and running, the foot acts like a flexible viscoelastic object that cushions impact and stores elastic energy. To characterize the functioning of the foot as a spatially extended and flexible object, we require all components of the ground traction forces to be measured with sufficient spatial and temporal resolution. We present here the theoretical underpinnings of a method based on photoelasticity to measure these traction forces with millimeter scale spatial, and millisecond temporal resolution.