Gait Stability and Aging

Stability is an important concept in biomechanics. It means that a mechanical system in equilibrium should resist changing its motion properties after an external perturbation. Gait is one of the most common ways of locomotion in humans. Walking is a motor action achieved by the interaction of the nervous system, muscles, joints, and bones with the environment and its external forces. Moreover, unhealthy conditions can change how older people walk when they cause motor impairments. Therefore, it is important to comprehend how individuals deal with an external perturbation to maintain their walking pattern, i.e., how to control the body to keep it stable during walking. The aim of this chapter is to describe the tools based on the dynamical systems approach that are built to evaluate the stability during gait with a focus on aging. Concepts of dynamical systems in gait analysis, the main concerns when applying those tools, and how the most common biomechanical variables applied to gait analysis should be prepared for that purpose.