Required coefficient of friction during turning at self-selected slow, normal, and fast walking speeds

Abstract

This study investigated the relationship of required coefficient of friction to gait speed, obstacle height, and turning strategy as participants walked around obstacles of various heights. Ten healthy, young adults performed 90° turns around corner pylons of four different heights at their self selected normal, slow, and fast walking speeds using both step and spin turning strategies. Kinetic data was captured using force plates. Results showed peak required coefficient of friction (RCOF) at push off increased with increased speed (slow µ= 0.38, normal µ=0.45, fast µ=0.54). Obstacle height had no effect on RCOF values. The average peak RCOF for fast turning exceeded the OSHA safety guideline for static COF of µ>0.50, suggesting further research is needed into the minimum static COF to prevent slips and falls, especially around corners.

Corner height influences center of mass kinematics and path trajectory during turning

“…The full procedure and overheard view of the set-up was reported by Fino and Lockhart (2014). Briefly, participants walked along a 0.75 m wide marked path with a 90° turn.…”

“…Prior testing revealed gait adjustments and slips when performing the task. The tape successfully increased the available friction of the floor allowing the participants’ natural actions to be observed without any adaptations (Fino and Lockhart, 2014). Participants wore their own athletic shoes throughout the experiment.…”

“…Previous studies have used objects to demark a corner (Grasso et al, 1998) or prevent participants from crossing through a corner (Glaister et al, 2008; Glaister et al, 2007b), but there is currently no knowledge concerning how the object’s shape or size influences the participants’ kinematics. Our earlier analysis reported no effect of obstacle height on RCOF during the push-off phase of gait (Fino and Lockhart, 2014) but did not examine other phases of the turn nor reported COM trajectories. Given that most turns in a crowded environment are to avoid obstacles (Glaister et al, 2007a), it is worth investigating whether the geometry of those obstacles impacts the resulting maneuvers and influences fall risk.…”

“…Turning requires a much larger required coefficient of friction (RCOF) to prevent slips (Fino and Lockhart, 2014) and has a higher incidence of falls resulting from slips (Yamaguchi et al, 2012a) than straight walking due to the lateral displacement of the COM relative to the base of support (BOS). Larger turning radii affect the orientation of the head and trunk (Sreenivasa et al, 2008), increase the COM displacement outside the BOS (Hollands et al, 2001), and decrease the walking velocity (Dias et al, 2013).…”

“…The RCOF at weight acceptance was hypothesized to increase with obstacle height and speed. The COM and COP clearance and θ ML were expected to increase with speed (Fino and Lockhart, 2014; Orendurff et al, 2006) and be greater for step turns compared to spin turns (Taylor et al, 2005). …”