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

Comparisons of ground reaction forces (GRF) during gait are not typically c onducted with blinding of the varied shoe characteristic, raising concerns related to the existence of a placebo effect, or a subject response based o n a perceived expectation of change. Purpose: To determine whether investig ator comments on shoe construction influenced GRF measures and ratings of s hoe cushioning during walking. Methods: 19 female college students voluntee red for a study presented as a test of a new shoe material. The study invol ved walking (2.5 m.s(-1)) under three shoe conditions (SC). Shoes in SC2 an d SC3 were harder than those in SC1, but shoes in SC1 and SC3 looked simila r. 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 cons tructed of unique new material. A control group performed the same three co nditions without investigator description. GRF data were collected for 10 t rials for each subject in each condition, and subjects rated the perceived cushioning of each shoe. GRF data and perceived cushioning scores were anal yzed using mixed-factor (group by shoe) ANOVA. Results: A significant shoe main effect was found for loading rate. Post hoc tests identified the diffe rence between SCI and both SC2 and SC3. The group main effect was not signi ficant for any dependent variable. Conclusions: Results suggest that, as a group, GRF data and cushioning scores are not affected by investigator comm ents that do not match shoe construction characteristics. However, ratings of perceived shoe cushioning by some individual subjects reflected investig ator comments and not the vertical GRF variables.