Temporal changes in the required shoe-floor friction when walking following an induced slip

Biomechanical aspects of slips and falls have been widely studied to facilitate fall prevention strategies. Prior studies have shown changes in gait after an induced slipping event. As such, most researchers only slip participants one time to avoid such changes that would otherwise reduce the external validity of experimental results. The ability to slip participants more than once, after allowing gait to return to a natural baseline, would improve the experimental efficiency of such studies. Therefore, the goal of this study was to characterize the temporal changes in required shoe-floor friction when walking following an induced slip. Two experiments were completed, and each employed a different potential strategy to promote the return of gait to a natural baseline after slipping. In the first experiment, extended time away from the laboratory was used to promote the return of gait to baseline. We measured required coefficient-of-friction among 36 young adult male participants over four sessions. The first three sessions provided measurements during baseline (i.e., natural gait) both prior to slipping and immediately after slipping. The fourth session provided a measurement 1-12 weeks after slipping. In the second experiment, an extensive number of walking trials was used to promote the return of gait to baseline. We measured required coefficient-of-friction among 10 young adult male participants in a single session. Measurements were collected during 10 baseline walking trials, immediately after slipping, and during 50-55 additional trials. In both experiments, required coefficient-of-friction decreased 12-16% immediately after a single slip, increased toward baseline levels over subsequent weeks/walking trials, but remained statistically different from baseline at the end of the experiments. Based on these results, experiments involving slipping participants multiple times may not have a high level of external validity, and researchers are encouraged to continue to limit experimental protocols to a single induced slip per participant.