The effects of perturbation intensities on backward slip-falls induced by a split-belt treadmill

Fall-inducing systems have two critical applications. One is to obtain the biomechanical features of falling, and the other is to systematically train individuals and reduce the risk of falling. While the former application necessitates the occurrence of falls, the latter does not require fall-inducing perturbations to be excessively intense. The purposes of the study were to investigate the effects of perturbation intensities (a combination of speeds and durations) on the number of falls, fall rates, and maximum loading forces resulting from slips induced by a split-belt treadmill. Twenty-four young adults (12 males and 12 females) completed 16 randomized trials (12 perturbation trials and 4 false trials). The forces between a safety harness and a rail were used to identify falls and non-falls and to assess the maximum loading force during falls. Although the number of falls, fall rates, and maximum loading force significantly increase as the slipping speed increases for both durations, the relative risk analysis shows that fall risk significantly increases as the slipping speed increases regardless of the duration. These findings may contribute to developing design criteria for controlled perturbations using a split-belt treadmill, aimed at enhancing our understanding of fall biomechanics and informing fall prevention training programs.