Stability and movement organization during beam walking in older adults

Abstract

Aging affects several skills, such as gait and posture. Balance during gait is a critical factor in determining the quality of life, but it is complex to be evaluated. Tests with this purpose have been developed for clinical practice, but they are not usually sensitive to discriminate intermediate balance levels. Walking on a balance beam involves the reduction of the base of support, accuracy on the foot placement and a small rise in the height at which the gait is performed, which causes greater difficulty than just walking on the ground. The use of several beam widths may be an efficient way to discriminate different balance levels over the use of a single, fixed beam width. Since mechanical (i.e., arms position) and cognitive factors may also influence beam walking performance, the understanding of the effects of these factors may contribute to the development of adequate balance tests. Thus, the first aim is to investigate the effect of the beam width, arms position and cognitive task in the stability during the beam walking in the older adults (study 1). Equally important is to understand how the older adults organize their motor activity to walk in an unstable context, such as the beam walking. Muscle coordination involves the use of flexible combinations of motor modules to produce a motor behavior that can be evaluated based on consistency, distinction, and separation of these modules. Aging can cause great variability in these coordination patterns and reorganization of motor modules. Thus, the second aim is to investigate the effects of age, beam width, arm configuration and cognitive task on the muscular organization during the beam walking (study 2). In study 1, 20 older adults will walk on a straight line on the ground and on 6, 8 and 10 cm wide beams (2 cm high and 4 m long). The arms will remain free, crossed on the chest or in the akimbo position. The cognitive task will be the sequential subtraction. Thirty-nine markers will be positioned at specific anatomical points and the Vicon system will track their displacements. It will be computed the spatial-temporal walking parameters (step length, duration and speed, and duration of the single and double support), the distance traveled in the beam, and the margin of dynamic stability. Analyzes of variance will be used to investigate the effects of the different factors on the dependent variables. In study 2, 15 young and 15 older adults will walk over a line on the ground and on the beam with a width defined based on study 1. The same 39 markers will be used and tracked by the Vicon system together with 14 electromyography electrodes that will monitor the muscle activity of the right leg and trunk. Participants will walk with free arms and arms crossed on the chest, with and without the presence of the cognitive task described in study 1. The same walking variables described in study 1 will be computed, with the addition of the motor modules analysis. It will also be used analyzes of variance to investigate the effect of the factors manipulated in study 2 on the walking performance and motor modules. The level of significance for all statistical analyzes will be 0.05. (AU)