The purpose of this study was to investigate the shock absorbency of fat pad in the heels (heel pad) of elderly individuals. Twenty healthy elderly males and females aged between 60 and 86 years and 10 young males and females participated in this study. A drop impact testing system, developed by the present investigators, was used for the measurement of shock attenuation characteristics of the heel pad. The testing system consisted of an instrumented shaft (wt : 5 kg) which could measure acceleration and displacement of the shaft. The shaft was released from two different heights (20 mm and 50 mm from the surface of the heel) to impact 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 planter-flexed at 90 degree angle and it was fixed to a surpport board using nylon belts. The acceleration and displacement signals were first recorded and analyzed. The peak deceleration, time to peak deceleration, peak deformation of the heel, time to peak deformation, and energy absorption were calculated and evaluated. Ground reaction force during normal walking was also measured for each subject to evaluate their walking patterns.
　It was found that with aging the peak deceleration of the drop shaft increased, and the value of energy absorbed by the heel pad decreased. The capacity to absorb impact shock by the heel pad for the elderly was estimated to be about 90% of that for the young individuals. The peak ground reaction force, normalized by their body weight, was greater and the total support period was longer for the elderly subjects than those for the young subjects. These suggest that the elderly people walk with lower impact force and at a slower step frequency. The lowered shock absorbency of the heel pad in the elderly needs some attention for the designers of walking and running shoes and playing surfaces of the gymnasium. There may also need some changes in play rules and training methods allowing the elderies to have less stress on their heel pads.

DESCENTE SPORTS SCIENCE Vol.16/THE DESCENTE AND ISHIMOTO MEMORIAL FOUNDATION FOR THE PROMOTION SPORTS SCIENCE