The effect of comments about shoe construction on impact forces during walking

Comparisons of ground reaction forces (GRF) during gait are not typically conducted with blinding of the varied shoe characteristic, raising concerns related to the existence of a placebo effect, or a subject response based on a perceived expectation of change.

To determine whether investigator comments on shoe construction influenced GRF measures and ratings of shoe cushioning during walking.

19 female college students volunteered for a study presented as a test of a new shoe material. The study involved walking (2.5 m x s(-1)) under three shoe conditions (SC). Shoes in SC2 and SC3 were harder than those in SC1, but shoes in SC1 and SC3 looked similar. Subjects in a mislead group (N = 9) were told SC1 and SC3 were baseline measures in a standard shoe, with SC2 misleadingly described as a shoe constructed of unique new material. A control group performed the same three conditions without investigator description. GRF data were collected for 10 trials for each subject in each condition, and subjects rated the perceived cushioning of each shoe. GRF data and perceived cushioning scores were analyzed using mixed-factor (group by shoe) ANOVA.

A significant shoe main effect was found for loading rate. Post hoc tests identified the difference between SC1 and both SC2 and SC3. The group main effect was not significant for any dependent variable.

Results suggest that, as a group, GRF data and cushioning scores are not affected by investigator comments that do not match shoe construction characteristics. However, ratings of perceived shoe cushioning by some individual subjects reflected investigator comments and not the vertical GRF variables.