Background: The purpose of the present study was to examine the metabolic cost of dual-task performance of a cognitive task while walking under two conditions: comfortable and fast gait speed.
Methods: Twenty-five healthy young adults (25.7±3.05 years) walked over-ground at a comfortable self-selected speed and on a treadmill at a fast speed with and without performing a cognitive task. Cardiopulmonary parameters were measured by the metabolic K4b2 system, gait parameters were measured with GaitRite and cognitive performance was expressed as percentage of correct answers to a set of riddles.
Results and conclusions: During rest, cognitive load resulted in a metabolic cost indicated by a significant increase in VO2 (p<0.01). Breathing rate increased significantly during dual-tasking in both walking conditions (p<0.01 for both). Fifty-two percent of the participants decreased gait speed during the dual-task condition while walking over-ground, accompanied by a significant decrease in tidal volume (p<0.01) without a decrease in breathing and heart rates. More than 70% of the participants improved or maintained their cognitive performance while walking (over-ground, 72% and treadmill, 75%), independently from the alterations in gait speed. The current findings confirm that mental processing increases energy demands while sitting. In addition, the results contribute new insight into dual-task paradigm research, by showing that breathing rate is sensitive to an additional cognitive load while walking, even in young healthy adults. Moreover, the participants were able to adjust the strategy they used to cope with cognitive load while walking over-ground when gait speed was imposed.