Abstract

The current study evaluated the importance of attention in motor control. In a dual task paradigm, 24 younger ( M = 21, SD = 2.00, range: 18-30 yrs) and 24 older ( M = 70.5, SD = 5.00, range: 62-80 yrs) adults' attention was divided between walking on a treadmill and performing a semantic judgment. For the semantic task, words were presented auditorally and participants judged if the word was living or non-living. When walking, muscle preparatory activity was measured with electromyography (EMG). Performance was measured at two different levels of walking difficulty: level (0{493}), and downhill (-15{493}). Measures of single task performance were compared to measures of dual task performance, in order to derive a proportional dual task cost for each condition. When performing two tasks at once, it was expected that older adults (OA) would allocate more attentional resources to walking at the cost of slower responses to the semantic task. Further it was predicted that the preparatory muscle activity of OA would diminish under dual task conditions. Contrary to predictions, under dual task conditions, all participants significantly improved their response times, [ F (1, 46) = 29.13, p < .001, j = 0.39] and experienced no changes in muscle activity. Across conditions, OA were slower at responding and had less muscle activity than the younger adults. In this study, the combination of tasks somehow facilitated a speedier response for the cognitive task. Cognitive capacity, task difficulty, and the demand characteristics of the testing are discussed.