Visual guidance to force plates does not influence ground reaction force variability

Gait analysis methods commonly require the subject to avoid visual guidance, that is, targeting, the force plate upon which a foot-strike is necessary. The putative rationale underlying the preference for not using targeting is the unsubstantiated contention that gait is altered. This study evaluated the influence of force plate targeting on the variability of ground reaction forces (GRF) in 15 normal subjects. Secondary factors of single vs multiple steps to the force plate and whether or not subjects were informed of the study's primary purpose were also examined. ANOVA main effects revealed that targeting did not significantly affect GRF variability (p > 0.05). A significant main effect of the number of steps required to reach the force plate on AP force variability was found (p = 0.002). Prior knowledge of the purpose of the study did not significantly affect GRF variability (p > 0.05). It was concluded that the variability of ground reaction forces is not significantly affected by targeting the force plate. Thus, targeting would not be expected to influence the variability of calculated kinetic variables that are subservient to GRF.