The effectiveness of shock-absorbing insoles during normal walking.

This paper describes a study of the effectiveness of commercially available shock absorbing insoles when used in four different pairs of shoes during normal walking. The measurement method was based on the use of the Fourier Transform of the axial acceleration of the leg measured by an accelerometer mounted at the ankle. The magnitude of shock was measured by the "Shock Factor" which has been defined as the rms acceleration between 50 Hz and 150 Hz expressed as a proportion of that between 10 Hz and 150 Hz. Nine insoles were tested in each pair of shoes and the Shock factor for each combination was compared with the value obtained for the shoes alone. Statistically significant reductions of Shock Factor were noted in 58% of cases; the largest improvement (30% reduction in Shock Factor) was achieved by lightweight Sorbothane. The experimental technique has now been further developed to allow the measurement of Shock Factor by a portable Shock Meter.