Higher entropy in movements may promote enhanced upper limb motor precision

The Optimal Movement Variability Hypothesis posits that healthy movements exhibit an optimal structure of variability, characterized by fractal patterns, which confer both stability and flexibility in motor control. This optimal, fractally-structured, variability has been associated with reduced metabolic cost during walking and enhanced resilience to perturbations. However, the full extent of the potential benefits of this variability remains largely unexplored. Our study aims to investigate whether training sessions involving movement synchronization to a variable fractally structured auditory cueing device can also enhance dexterity and reduce miss percentage in a Fitts' law task. Twenty-four participants were randomly assigned to three groups: two groups received training involving wrist oscillations synchronized to an auditory cue with a fractal structure or self-paced wrist oscillations without a cue, while the third group received no training. Following four training sessions, the training groups completed a post-Fitts' Law task to assess any improvements in dexterity, while the untrained group completed the post-Fitts' Law task two weeks after their initial assessment. The results indicated that all groups improved accuracy, although there was no enhancement in the speed of striking the targets. Contrary to our hypothesis, the fractally structured auditory cued training group did not demonstrate superior performance compared to the self-paced and no-training groups. However, subjects who showed improvement on the post-Fitts' Law task exhibited higher movement sample entropy during the training task, irrespective of the training group they were in. These results suggest that while a generalized fractal variability training program may not enhance dexterity for young adults, individuals with high movement unpredictability may possess a greater capability for motor learning.