Utilized coefficient of friction during walking: static estimates exceed measured values

This study compared utilized coefficient of friction (COF) measured during nonslip pedestrian gait to estimated utilized COF values calculated using anthropometric (i.e., leg length) and stride characteristic data (i.e., impact angle, step length). Twenty healthy adults walked at slow, medium, and fast speeds with kinematic and kinetic data recorded simultaneously. Estimated and measured impact angle varied with walking speed, with greater angles evident with faster speeds (p < 0.001 and p < 0.05, respectively). The estimated impact angle was greater than the measured impact angle (p < 0.05). Estimated and measured peak utilized COF values varied with walking speed, with higher utilized COF values evident with faster speeds (p < 0.001 and p = 0.001, respectively). Estimated utilized COF values were 86, 118, and 131% greater than measured peak utilized COF values for slow, medium, and fast speeds, respectively (p < 0.001). Higher estimated utilized COF values varied moderately with increased measured peak utilized COF values (r = 0.522; p < 0.001). These data suggest that impact angle and step length alone cannot be used to accurately assess the utilized COF on level walking surfaces.