Coordination between motor and cognitive tasks in dual task gait

Background: Dual Task (DT) paradigms are frequently used by researchers and clinicians to examine the integrity of motor processes in many movement disorders. However, the mechanism of this interaction is not fully understood. Therefore, the aim of this study was to examine the within-stride interactions between cognitive and motor processes during dual task gait (DT). Research question: Do healthy young adults coordinate gait with secondary task processing? If so, is cognitive task processing capability associated with the coordination observed? Methods: Nineteen healthy young adults walked for two minutes on a motorized treadmill whilst counting backwards in sevens from three-digit numbers. The coordination of calculation verbalizations with gait parameters were assessed across six phases of the gait cycle. Mid verbalization time points (VER_Mid) were used as points of high cognitive processing of the dual task and compared with the end of the verbalizations (VER_End) as points of low cognitive processing. Results: VER_Mid and VER_End did not systematically occur in any phase of the gait cycle. However, 10/19 and 9/19 participants showed non-random distributions of verbalizations for VER_Mid and VER_End time points respectively (p < 0.01), indicating that these walkers coordinated gait with the cognitive task. Analysis of subgroups of Verbalization Coordinators and Non-Coordinators showed slower verbalization response durations (VRD) for VER_Mid Coordinators compared to VER_Mid Non-Coordinators, indicating that VER_Mid Coordinators found the cognitive tasks more demanding. No differences were found in VRD for VER_End Coordinators and VER_End Non-Coordinators. Significance: It was found that cognitive processing is coordinated with gait phases in some but not all healthy young adults during DT gait. When demands on cognitive processes are high, healthy young adults coordinate cognitive processing with phases of gait. Analysis of within-stride coordination may be of use for studying clinical conditions where gait and attentional cognition performance breaks down.