The aim of this study is to analyze dual-task effects on free and adaptive gait in Alzheimer's disease (AD) patients. Nineteen elders with AD participated in the study. A veteran neuropsychiatrist established the degree of AD in the sample. To determine dual-task effects on free and adaptive gait, patients performed five trials for each experimental condition: free and adaptive gait with and without a dual-task (regressive countdown). Spatial and temporal parameters were collected through an optoelectronic tridimensional system. The central stride was analyzed in free gait, and the steps immediately before (approaching phase) and during the obstacle crossing were analyzed in adaptive gait. Results indicated that AD patients walked more slowly during adaptive gait and free gait, using conservative strategies when confronted either with an obstacle or a secondary task. Furthermore, patients sought for stability to perform the tasks, particularly for adaptive gait with dual task, who used anticipatory and online adjustments to perform the task. Therefore, the increase of task complexity enhances cognitive load and risk of falls for AD patients. 1. Introduction Elderly people with Alzheimer’s disease (AD) show reduced gait performance [1], such as a slow and irregular stride [2]. Gait adjustments of patients with AD have been explained by frontal lobe dysfunctions, especially in the motor cortex [2, 3], and by an intense decrease in executive functions [3]. Moreover, patients with AD have a less automated gait [1, 4], especially when a concurring executive task (dual task) is performed. Furthermore, elderly people with AD are more prone to falls when compared to healthy elders [5], falling 4 to 5 times a year [6]. Studies have shown that touched or stumbled on the obstacles are one of the major causes for falls in AD patients [7]. The studies of the dual-task effects during gait in AD patients have focused on free gait [8]. However, AD patients do not walk only on even terrain during their daily activities. They need to adapt their locomotor behavior to different travel surfaces. Dual-task effect on adaptive gait (walking characterized by presence of obstacles that demand adaptive strategies) in AD patients is poorly understood [9]. Adaptive gait competes with the executive task for attention and planning functions, especially due to previously observed relationships between performing complex motor tasks and executive functions [3, 10, 11]. Therefore, dual task during adaptive gait seems to be more challenging for AD patients. The aim of this study is to
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