Mechanical inputs related to perception of lower extremity impact loading severity

Human responses to repetitive locomotor loadings are likely dependent upon the perceived severity of the impact. Few researchers have attempted to identify the mechanical variables upon which perception of impact severity is based. This study examined the relationship of selected impact loading variables to the perception of impact severity by employing an established psychophysical test procedure.

A human pendulum apparatus was used to administer and measure impact loadings similar to those encountered during running. Nineteen subjects experienced over 100 right foot impacts which comprised nine different impact conditions presented in a random manner. The conditions represented combinations of three impact velocities and three interface materials covering a force platform.

Group mean subjective ratings of impact severity were highly related to all measured biomechanical descriptors of impact severity. The variables of impact force rate of loading (FRA) and peak shank acceleration had correlation coefficients of 0.99 with perceived severity. When all individual results were combined to determine the relationship of impact loading variables to perception, correlations were generally 0.7 or above with FRA alone explaining 64% of the perceptual rating variability.

These results indicate that impact perception was highly associated with the mechanical input variables commonly measured and that midsole materials such as those typically found in athletic footwear do not remove our ability to perceive the severity of impact loads.