The shock absorbing characteristics of the biological structures located underneath the heel bone were investigated using a drop tester developed by the present investigators. The tester consisted of an instrumented shaft which could measure an acceleration and dis-placement of the dropper (wt : 5 kg). The dropper was released from two different heights (30 mm and 50 mm from the surface of the heel) to hit the center of right heel of the subject. The subject laid on the stomach on a height adjustable floor while his/her right knee was flexed at a right angle to the floor. The ankle of the right foot was plantar-flexed at 90 degree angle and it was fixed to a support board using nylon belts. Fourteen adults (8 females and 6 males) and 3 children aged 7 yrs. served as subjects for the study. The data were sampled at 2 KHz on line mode using an A/D converter and a lab computer system.
　It was revealed that average peak accelerations were 8.5 G and 11 G for 30 mm and 50 mm drop-height conditions, respectively. The maximum deformations for the corresponding conditions were 10 mm and 12 mm. A computed energy loss was 76% (ranged between 72 and 84%) for both drop heights, suggesting that the heel structure had a high viscous element. There was a fair correlation (P< 0.05) between an average skinfold thickness and each of the measured parameters (peak acceleration, peak deformation, time to peak deformation, and the energy loss). Better shock absorbing characteristics were revealed for individuals with thicker skinfold measurement.
　It was concluded that the heel properties were fairly an effective shock absorber, and its mechanical characteristics depended on the thickness of the fat tissue. It was also concluded that the drop tester which was designed and constructed by the present investigators was a reliable and reproducible method to measure the heel cushioning characteristics.

DESCENTE SPORTS SCIENCE Vol.12/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE