Dual-task prioritization during overground and treadmill walking in healthy adults

Background: The dual-task effect on walking performance is different during treadmill and overground walking, though the cause of this difference is unknown. This study examined the effects of task prioritization on overground and treadmill dual-task walking. Method: Twenty-two adults walked overground and on a treadmill under three dual-task conditions: prioritization of walking performance, prioritization of cognitive performance (serial subtraction in sevens), or no prioritization. Results: Compared to single-task walking, stride velocity was reduced and stride time variability was increased during dual-task overground walking. During treadmill walking, there was no dual-task effect on walking performance, but cognitive task performance was improved. Prioritization of the cognitive task reduced the dual-task effect on stride velocity during overground walking only, whilst prioritization of the walking task reduced cognitive task performance in both walking modalities. Significance: These results corroborate recent findings that the dual-task effects on treadmill walking are not equivalent to those on overground walking. Healthy adults appear to prioritize cognitive task performance during treadmill dual-task walking without detrimental effects to gait. During overground walking however, allocation of attention to the secondary task reduces gait performance. These results indicate that treadmill based dual-task paradigms should not be used to infer factors which influence the cognitive control of overground walking.