How do the elderly negotiate a step? A biomechanical assessment

Abstract

Tripping over a raised surface is considered to be the most common cause of falls in the elderly. The aim of this study was to detect alterations of the motor pattern of elderly subjects while climbing a single step ("one step negotiation") which may account for tripping and risk of falling. We tested a sample of 32 "healthy" elderly subjects with a mean age of 72.4 years (SD 4.81; range 65-86). The control group consisted of 18 young subjects with a mean age of 26.5 years (SD 2.12; range 24-33). An experimental set-up for kinematic assessment while climbing a single step was provided. The elderly population was characterized clinically and functionally by a comprehensive geriatric assessment including information about comorbidity, disability, depression, motor, and muscular function. Despite the high level of motor ability measured clinically, biomechanical analysis enabled us to demonstrate precise changes in step-climbing strategy in the elderly. A prolonged double stance phase duration, a greater anterior flexion of the trunk, a greater flexion of the hip, and a reduced dorsiflexion of the ankle were detected with respect to controls. All these factors and especially the latter could be determinants in the possible risk of tripping. The biomechanical analysis performed on a population of healthy elderly subject has shown precise abnormalities of the trunk, hip and ankle kinematic during the motor task execution. This information can be of relevance in planning physical activity programs adapted for elderly and aimed at reducing the risk of tripping and falling.