Age-Associated Declines in Complex Walking Task Performance: The Walking InCHIANTI Toolkit

Mobility, defined as the ability to walk safely and independently in one’s environment, is critical to maintaining independence in activities of daily living (ADLs), in preserving social relationships and in ensuring quality of life.1,2 In older adults, impaired mobility predicts the onset of disability in tasks essential to living independently in the community and in caring for oneself.2,3 Mobility limitations tend to occur early in the process leading to ADL disability.2–5 Walking in daily life involves negotiating diverse environments with varying terrains (cluttered, slippery), ambient conditions (adverse weather, low light), and attentional demands (noisy or distracting environments). In addition, walking is often performed in conjunction with other tasks such as carrying loads, scanning the environment, changing directions, avoiding obstacles, or engaging in social interactions. Complex walking tasks (CWTs), involving adaptation to change in task and environmental demands, require physiological resources beyond those needed for walking under less-difficult conditions and so are reflective of mobility in home and community environs.6–8 Evaluation of mobility in older adults typically involves observing their speed, stability, step length, and foot clearance during self-paced walks performed on straight, uncluttered, and well-lit courses. Rarely do performance-based tests include walking under complex and challenging conditions such as those encountered in daily life. Recent research has shown that older adults who would be classified as independently mobile using standard measures demonstrate limitations in walking under more-complex conditions.8–10 Performance on complex tasks, such as the heel/toe walk and fast-pace walk with a pivot turn, is a good predictor of adverse health outcomes, including falls and fractures, suggesting that inclusion of complex locomotor tasks may be important in evaluating mobility limitations.11–13 The purpose of this article is to describe a set of CWTs that were used to evaluate mobility in a large sample of community-living older adults and to characterize age- and sex-specific performance on these tests. The current battery of walking tests was based on a person–environment interaction model of mobility disability, which proposes that factors within the physical environment mediate the relationship between functional limitations related to walking and the development of mobility disability. The tests measured walking performance in the face of physical challenges often encountered when walking in a community environment, such as walking while performing a secondary cognitive task, carrying a package, or stepping over one or more obstacles.6,9,10 Locomotor adaptation was further challenged by asking subjects to perform some tasks at a fast pace or for long distances. It was expected that performance on CWTs would be lower than on simple walking tasks and that the magnitude of the performance gap between simple tasks and CWTs would be higher in older persons. It was also expected that the variability of performance in CWTs would be greater in participants with higher performance in simple walking tasks.