The biomechanics of slips are an important component in the prevention of fall-related injuries. The purpose of this paper is to review the available literature on the biomechanics of gait relevant to slips. This knowledge can be used to develop slip resistance testing methodologies and to determine critical differences in human behaviour between slips leading to recovery and those resulting in falls. Ground reaction forces at the shoe-floor interface have been extensively studied and are probably the most critical biomechanical factor in slips. The ratio of the shear to normal foot forces generated during gait, known as the required coefficient of friction (RCOF) during normal locomotion on dry surfaces or 'friction used/achievable' during slips, has been one biomechanical variable most closely associated with the measured frictional properties of the shoe/floor interface (usually the coefficient of friction or COF). Other biomechanical factors that also play an important role are the kinematics of the foot at heel contact and human responses to slipping perturbations, often evident in the moments generated at the lower extremity joints and postural adaptations. In addition, it must be realized that the biomechanics are dependent upon the capabilities of the postural control system, the mental set of the individual, and the perception of the environment, particularly, the danger of slipping. The focus of this paper is to review what is known regarding the kinematics and kinetics of walking on surfaces under a variety of environmental conditions. Finally, we discuss future biomechanical research needs to help to improve walkway-friction measurements and safety.

No abstract

Pedestrian accidents generate significant direct, morbidity and mortality costs. Slip accidents are generally a result of a number of factors. One factor that has received considerable attention is the walkway-surface slipperiness. It is desirable to be able to isolate, to the extent possible, the contribution of the walkway surface to slipperiness. It has been the practice of those involved in evaluating walkway slip resistance to test the floor against a standard test foot under specified conditions and compare the results of that testing against a threshold. Those walkway surfaces that produce a friction coefficient above the threshold are considered acceptable. Past and present tests and associated thresholds are discussed. Abuse issues are discussed. It is recommended that field tests measure the available friction with a tribometer capable of correctly characterizing the friction model experienced by the pedestrian and compare that against a utilized friction threshold, determined by normative or force-plate means, for activities foreseeable in the area where a fall occurs.

Since the inception of interest in friction, the effect, if any, of contact pressure has been investigated. DaVinci, Amontons, and Coulomb, three early investigators, found no effect. The development of interest in walkway safety tribometry, the measurement of friction at the shoe-bottom/walking-surface interface, suggests a reassessment of the applicability of Amontons-Coulomb because the shoe bottom is resilient and because the interface between the shoe bottom and the walkway surface is frequently contaminated, for example, with a liquid such as water. In any such reassessment, the relationship between contact pressure and the friction coefficient becomes worthy of attention. Contact pressures in normal walking can vary upwards from a few psi to over a thousand psi (heelstrike in high-heeled shoes). This paper will explore the historical background and experimental research in the literature and present the results of our experiments which explore the relationships between contact pressure and friction. The effect on friction of test-foot sliding is experimentally analyzed. The relationship between the tribological results presented here and real-world walkway safety are discussed. The effect of test-foot polishing is analyzed. Future areas of investigation are discussed.

No abstract