IN-VIVO EXAMINATION OF THE DYNAMIC PROPERTIES OF THE HUMAN HEEL PAD

The shock-absorbing characteristics of the heel pad in vivo were exami ned in adults (N = 16) and 7-year-old children (N = 5) using a drop-im pact tester (wt = 5 kg). Impact velocities were 0.72 m/s and 0.93 m/s. It was found that in adults the average peak deceleration was 11.6 G at an impact velocity of 0.93 m/s. The maximum deformation of the heel pad was 11.3 mm, and the computed energy absorption during impact amo unted to 79% (range = 75%-89%). These mechanical characteristics remai ned nearly the same even after 6 min of repeated impacts by the impact tester and even after a 10 km run. The children had larger values of peak deceleration and maximum deformation and smaller energy loss than the adults. It was concluded that the heel pad was a fairly effective shock attenuator and high energy absorber, and that these characteris tics remain nearly unchanged even after a relatively long period of re peated impacts. It was also concluded that the mechanical properties o f the children's heel pads were different from those of the adults.