ABSTRACT

Walking is deceptively difficult. Even a cursory inspection allows some insight into the challenges of upright gait. It is not by accident that humans, when compared with other species, take much longer time to achieve proficiency with regard to mobility. Most other mammalian species have a low center of mass, and four limbs are used as a base of support; therefore, the ability to maintain the center of mass within this broad base of support, a definition of balance, is relatively easy. In contrast, human bipedal ambulation requires the ability to control and propel an elevated center of mass over just two limbs, which provides a narrow and variable base of support. In order to reliably accomplish this covertly athletic feat, the central nervous system requires timely and accurate information so as to make the motor adjustments necessary to maintain balance (1). This information arrives via the somatosensory, visual, and vestibular systems. Given the difficulty of the bipedal walking task, any distortion in this afferent flow of information may lead to impairments in balance and difficulty with mobility.