Exploring the Biomechanics of Double Slips

Author Aditya Jayadas
Co-Author James L. Smith
DOI

Country : USA
Subject : Design, Housing & Merchandising

Keywords : Double slips, slip distance ratio, step length ratio

Abstract

Background: Biomechanics of slips and falls have been explored by several researchers over the past decade. However, none of the researchers have explored the concept of double slips that occur as a result of a slippery perturbation.

Purpose: The question explored in the study was: what happens if individuals slip multiple times? The purpose of the study was to better understand double slips and also to establish relevant variables in understanding the biomechanics of double slips as they relate to fallers and non-fallers

Methods: Twenty-eight individuals (14 young and 14 elderly) with equal numbers of males and females participated in the study. Out of the 84 gait slip trials in the study, only 25 trials were used for analysis in this paper as only 25 trials resulted in double slips. Individuals were required to walk along a circular track and they were exposed to an ‘unknown’ slippery floor condition. The gait trials were monitored using an 8-camera motion capture system.

Two new variables were introduced while exploring recovery effort as it relates to double slips in individuals, namely slip distance ratio and step length ratio. Slip distance ratio was defined as the ratio of the distance slipped during the first slip to the distance slipped during the second slip. Similarly, the step length ratio was defined as the ratio of the step length just prior to the first slip to the step length just prior to the second slip.

Results: The results indicated that individuals with smaller slip distance ratio and higher step length ratio were able to recover better when compared to individuals with higher slip distance ratio and lower step length ratio. This suggests that individuals who slipped a greater distance during the second slip when compared to the first slip were more likely to fall. Also, individuals who took a shorter step after the first slip were more likely to fall.

Conclusion: Findings from this study provide new insight into double slips. Simple variables such as slip distance ratio and step length ratio could be used to predict falls and recovery from double slips. In terms of recovery effort, individuals could benefit from attempting to slip less the second time if they do encounter a double slip and more importantly take a larger step and place the foot safely and gently to reduce the likelihood of a fall resulting from a double slip.

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