Abstract

The influence of an attention demanding cognitive task on each phase of gait was analyzed, using a dual-task paradigm. Electromyography (iEMG) from eight muscles from the dominant leg was collected from 23 participants (age 18-27) while walking on a treadmill at a 20% increase of their self-selected speed and while walking and performing a cognitive task. The cognitive task consisted of subtracting one (EASY) or seven (HARD) from numbers aurally presented. Reaction time (RT) and accurate responses of the cognitive task were recorded. iEMG events were selected according to stimuli onset (0-150 ms, 150-300 ms and 300-450 ms) prior to the phases of gait (double-leg, single- leg and swing). There was a decrease in iEMG amplitude of fibularis longus (p = .013) and vastus lateralis (p = .065) while walking and performing the cognitive task. When stimulus onset was considered, iEMG of medial gastrocnemius (p = .021) and lateral gastrocnemius (p = .004) were reduced during single-leg stance, when stimuli occurred between 300-450 ms prior to this phase. Participants committed more errors and had longer RT on the HARD task. RT was longer when subtracting while walking in comparison to subtracting alone. Young adults expressed dual-task cost in the motor and the cognitive tasks, suggesting that walking requires attention. There was a specific moment (300 ms after stimulus onset) during single-leg stance that dual-task cost occurred. Reasons for this interference and the implications of a reduction in iEMG while walking and performing an attention demanding cognitive task are discussed.