A kinetic evaluation of the effects of in vivo loading on running shoes

The purpose of the study was to assess the effects of repeated in vivo loading on shock attenuation and mediolateral stability of running shoes using ground reaction force data. Six healthy subjects were each given a new pair of running shoes and asked to run 140 km between each of four experimental sessions. Ground reaction force data were collected for 10 successful trials/session using an A.M.T.I. force platform system. The mean values for selected ground reaction force parameters were evaluated using a single subject repeated measures design based on a 95% confidence interval. Mean parameter group data were also evaluated. The results support previous findings that material properties of the systems evaluated deteriorated resulting in a loss of shock absorbing capabilities (7.3%) but the magnitudes of the losses were far less than previously reported results (23-40%). The reason for this discrepancy is presumed to be the result of the different loading and evaluation methods used in the present study. The results also suggest that these changes are not totally deleterious since foot control seems to improve as cushioning is lost and foot control accounts for at least half of running shoe related injuries. A further implication of these results is that the initial "feel" or performance characteristics of a shoe may be misleading since reasonable functional changes appear to occur during the initial 300-400 km of wear.J Orthop Sports Phys Ther 1988;10(2):47-53.