Low frequency shock absorption in human walking

This study was designed to investigate the capability of the joints to absorb shock while walking at a constant speed on a treadmill under various frequency conditions. Eight subjects were required to walk at their preferred frequency, at a frequency predicted as the resonance of a hybrid pendulum-spring model of the legs and at metronome-driven frequencies ± 15%, ± 25% and ± 35% of the predicted frequency. Subjects were filmed in the sagittal plane. Shock absorption was calculated based on the ratios of mean peak two-dimensional (2-D) resultant accelerations between the ankle, knee, shoulder and head. A univariate measures ANOVA was used to compare shock absorption across all frequency conditions except the preferred. A U-shaped curve for frequency versus head:ankle shock absorption was observed with maximal absorption at the predicted frequency. The amount of shock reaching the head across conditions was small ranging from 8% of the shock at the feet at the predicted frequency to 15% at the lowest frequency. These findings suggest that minimization of shock to the head is an important constraint on gait regardless of the adopted frequency-stride length.