Abstract
Shock absorption (SA) is a simple way to reduce the body load and can be used in the
prevention and treatment of injuries. The heel pad is the most important shock absorber
in the shoe heel complex. The purpose of this study was to investigate whether the
SA at heel strike can be increased by heel support in people and shoes with high or
low SA. The impact forces at heel strike were measured on an AMTI (R) force platform.
Fourteen legs were tested in seven persons (nine with normal and five with low heel
pad SA) in gait analysis and in human drop tests. The tests were performed barefooted,
and in a soccer and a running shoe (selected by shoe drop test), with and without
the distal 2 cm of the heel counter. The heel pad confinement produced by the heel
counter (the heel counter effect) increased the SA in both shoe types significantly
in both impact sitations. The mean increase in SA was 8.8% (range 5.8%-15.5%). The
heel counter effect was in all situations significantly higher in persons with low
heel pad shock absorbency (LHPSA) than in those with normal heel pads. The barefoot
impact peak force per kg body weight was significantly higher (6%mean) on the side
with LHPSA. The running shoe provided the significantly greatest SA compared with
the soccer shoe. It is concluded that the shock absorbency at heel strike can be increased
significantly by heel support, with highest effect in persons with LHPSA, both in
shoes with high and low SA. This should be considered when chosing, constructing,
or testing shoes where an optimal shock absorbency is desired.
Key words
shock absorption - heel - overuse injuries - soccer - running shoes
