Abstract
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 actual occurrence of falls, the latter does not require fall-inducing perturbations to be excessively intense. This study investigated the effects of perturbation intensities (a combination of speeds and durations) on the number of falls, fall rates, and maximum loading forces resulting from backward slips induced by a split-belt treadmill. Twenty-four healthy young adults (12 males and 12 females), naïve to the purpose of the study, completed 16 randomized trials, including 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 can contribute to establishing design criteria for controlled perturbations in studies on the biomechanics of falls and fall prevention training.