Enforcing walking speed and step-length affects joint kinematics and kinetics in male and female healthy adults

Background: Individuals increase walking speed by increasing their step-length, increasing their step-frequency, or both. During basic training military recruits are introduced to marching "in-step", and thus the requirement to walk at fixed speeds and step-lengths. The extent to which individuals are required to under-or over-stride will vary depending on their stature, and the stature of others in their section. The incidence of stress fractures in female recruits undergoing basic training is higher than that for their male counterparts.Research question:: Therefore, the purpose of this study was to determine how joint kinematics and kinetics are affected by walking speed, step-length, and sex.Methods: Thirty-seven (19 female) aerobically active non-injured individuals volunteered for this study. Synchronised three-dimensional kinematic and kinetic data were collected while participants walked overground at prescribed speeds. Audio and visual cues were used to control step-lengths. Linear mixed models were run to analyse the effects of speed, step-length condition, and sex on peak joint moments.Results and Significance: The findings of this study showed that, in general, walking faster and over-striding pre-dominantly increased peak joint moments, suggesting that over-striding is more likely to negatively affect injury risk than under-striding. This is especially important for individuals unaccustomed to over-striding as the cumu-lative effect of increased joint moments may affect a muscles capability to withstand the increased external forces associated with walking faster and with longer step-lengths, which could then lead to an increased risk of developing an injury.