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 v arious frequency conditions. Eight subjects were required to walk at t heir preferred frequency, at a frequency predicted as the resonance of a hybrid pendulum-spring model of the legs and at metronome-driven fr equencies +/-15%, +/-25% and +/-35% of the predicted frequency. Subjec ts were filmed in the sagittal plane. Shock absorption was calculated based on the ratios of mean peak two-dimensional (2-D) resultant accel erations between the ankle, knee, shoulder and head. A univariate meas ures ANOVA was used to compare shock absorption across all frequency c onditions except the preferred. A U-shaped curve for frequency versus head:ankle shock absorption was observed with maximal absorption at th e predicted frequency. The amount of shock reaching the head across co nditions was small ranging from 8% of the shock at the feet at the pre dicted frequency to 15% at the lowest frequency. These findings sugges t that minimization of shock to the head is an important constraint on gait regardless of the adopted frequency-stride length.