Does dual task placement and duration affect split-belt treadmill adaptation?

Abstract

Background: Dual tasking during prolonged split-belt adaptation (10-15 min) has shown to slow the adaptation process and prolong aftereffects. Therefore, dual tasks during split-belt adaptation are being explored for their potential in gait symmetry rehabilitation. However, the ideal paradigm configuration it is still not clear.

Research question: To determine whether split-belt adaptation and ensuing aftereffects are altered by dual task placement, specifically looking at onset of split-belt adaptation or later part way through Adaptation (Experiment 1) and dual task duration (Experiment 2).

Methods: Healthy young adults (n = 40) performed 5 min of tied-belt walking, followed by 14 min of split-belts (Adaptation, 1:3 ratio) and 5 min of de-adaptation (both belts at same speed) to assess after effects (Post-Adaptation). Experiment 1: To assess the effects of dual task placement, an auditory version of an n-back task was presented during the first 8 min or last 8 min of Adaptation. Experiment 2: To assess the effects of dual task duration, the cognitive task was presented during the entire split-belt Adaptation phase (14 min) or during four 2-minute bouts (8 min). Cognitive task accuracy, dual support symmetry, and rates of adaptation and de-adaptation were compared.

Results: When both the onset of the auditory cognitive task and the onset of Adaptation (split-belts) occurred simultaneously, participants prioritized split-belt adaptation and in doing so, cognitive task accuracy was reduced (Experiment 1). By prioritizing gait symmetry over cognitive performance, there were no differences in dual support symmetry adaptation (magnitude, variability or rate of Adaptation/De-adaptation) regardless of cognitive task placement or duration (Experiment 2).

Significance: We believe the early portion of split-belt treadmill adaptation to be a cognitive interference period. These results support future work exploring the use of dual task in a rehabilitation setting with more complicated motor-cognitive dual task paradigms during this key period.

Keywords: Dual-task; Gait adaptation; Split-belt treadmill.