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.

Gait accelerometry is a promising tool to assess human walking and reveal deteriorating gait characteristics in patients and can be a rich source of clinically relevant information about functional declines in older adults. Therefore, in this paper, we present a comprehensive set of signal features that may be used to extract clinically valuable information from gait accelerometry signals. To achieve our goal, we collected tri-axial gait accelerometry signals from 35 adults 65 years of age and older. Fourteen subjects were healthy controls, 10 participants were diagnosed with Parkinson's disease, and 11 participants were diagnosed with peripheral neuropathy. The data were collected while the participants walked on a treadmill at a preferred walking speed. Accelerometer signal features in time, frequency and time-frequency domains were extracted. The results of our analysis showed that some of the extracted features were able to differentiate between healthy and clinical populations. Signal features in all three domains were able to emphasize variability among different groups, and also revealed valuable information about variability of the signals between anterior-posterior, mediolateral, and vertical directions within subjects. The current results imply that the proposed signal features can be valuable tools for the analysis of gait accelerometry data and should be utilized in future studies.

Temporal dynamics of attention during postural perturbations in young and older adults were investigated. Nineteen young and older subjects performed simple reaction time tasks during translational platform perturbations. Auditory or visual stimuli were presented randomly at delays from the onset of the platform perturbation. Reaction time was slowed before and during the platform movement, particularly in older subjects. Reaction times to stimuli presented at a 250-millisecond delay or later were not influenced by perturbation. The reaction times to the auditory stimuli were influenced more by perturbation than were those to visual targets. The postural response was unaltered by the presence of the reaction time task, but it differed between groups. Attention is engaged in response to a perturbation during the preperturbation time and during the initiation of the postural response in young and older adults. Sensory selection occurs in young and older adults, but to a greater degree in older subjects.

We examined outcomes in persons with vestibular disorders after receiving virtual reality based therapy (VRBT) or customized vestibular physical therapy (PT) as an intervention for habituation of dizziness symptoms. Twenty subjects with vestibular disorders received VRBT and 18 received PT. During the VRBT intervention, subjects walked on a treadmill within an immersive virtual grocery store environment, for six sessions approximately one week apart. The PT intervention consisted of gaze stabilization, standing balance and walking exercises individually tailored to each subject. Before, one week after, and at six months after the intervention, subjects completed self-report and balance performance measures. Before and after each VRBT session, subjects also reported symptoms of nausea, headache, dizziness, and visual blurring. In both groups, significant improvements were noted on the majority of self-report and performance measures one week after the intervention. Subjects maintained improvements on self report and performance measures at six months follow up. There were not between group differences. Nausea, headache, dizziness and visual blurring increased significantly during the VRBT sessions, but overall symptoms were reduced at the end of the six-week intervention. While this study did not find a difference in outcomes between PT and VRBT, the mechanism by which subjects with chronic dizziness demonstrated improvement in dizziness and balance function may be different.