Analysis of Leg Loading in Snow Skiing

Abstract

The complete excitation between the boot and ski was measured during skiing. Data from strain-gage force transducers mounted inside the test ski were FM transmitted to a receiving station about 3 km distant. Three skiing maneuvers (snowplow, stem christiana, parallel christiana) were tested and data from authentic falls were also recorded. Data were plotted in real-time and analyzed by digital computer. The loading histories reveal that the nonstationary loading is related to maneuver type. Torsion and bending component amplitudes, measured at the boot sole, are approximately equal to the static tibia ultimate strength in bending and torsion during both elementary skiing maneuvers and falls. In these high amplitude loading situations the skier was not injured. Data were analyzed for spectral content by the Fast Fourier Transform (FFT). Results show a 3.5 Hz cutoff frequency common to all load components and maneuvers. 3.5 Hz is a reasonable corner frequency for the human controller. Results suggest that below 3.5 Hz the skiing excitation is primarily muscle induced while above 3.5 Hz the excitation is due to ski-snow interaction.