Date of Award

7-2024

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Biomechanics Research Building

First Advisor

Dr. Aaron D. Likens

Abstract

Coordination is the organization of a system’s components to achieve collective behavior, whether within an individual or across systems. Coordination may be either monofrequency, the systems oscillating at the same frequency (e.g. 1:1), or multifrequency, the systems oscillating at unique frequencies (e.g. 1:3). Multifrequency coordination is typically described by the sine circle map (SCM); however, several limitations arise when describing human movement. Healthy young adults' movements exhibit Pink noise, a pattern in the timing of their actions that enables them to adapt flexibly to environmental changes by resulting in well-coordinated behavioral adjustments. The SCM fails to capture the natural variability in human movement. This thesis aimed to modify the SCM and explore experimentally the hypothesis that movement variability influences the performance of multifrequency coordination. Participants performed a bimanual multifrequency wrist flexion/extension task, pacing their dominant hand to regular (Isochronous) and irregular (White, Pink, Brown noise) auditory metronomes. Participants produced three intended ratios (1:2, 1:3, 1:4) at slow and fast speeds. The frequency ratio between the two hands was evaluated on a cycle-by-cycle basis. Our results demonstrated that 1) Slow speeds produce greater accuracy across all ratios relative to fast speeds, 2) Amongst ratios, accuracy during slow speeds followed the order of 1: 2 ≥ 1: 3 ≥ 1: 4, whereas this pattern reversed for fast speeds 1: 4 > 1: 3 > 1: 2, and 3) The temporal structure of the metronomes did not affect accuracy at slow speeds; however, at fast speeds, Isochronous was generallymore accurate than Pink noise, though the trends were somewhat inconsistent across different ratios and noises. Exploratory analysis revealed that the observed inaccuracy in Pink noise during fast speed led to the more stable ratio of 1:4, in contrast to the other noises, emphasizing its heightened adaptability. Although none of the simulated SCM equations described the experimental patterns, the findings from this thesis suggest the need for an integrative model involving elements of both dynamical systems theory and the inherent variability in human movement to develop a new equation that accurately captures multifrequency coordination in human movement.

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