Change in control intermittency with practice during humanpostural balancing on an unstable unrestrained platform

Purpose: The central nervous system (CNS) employs an intermittent control strategy in humanquiet stance and other balancing activities as stated in the literature. We investigate the less exploredaspect of how the intermittent control strategy changes as humans practice balancing on an unstableunrestrained platform. Method: We perform human subject experiments with a rocker board, obtain the Center of Pres-sure (COP), ankle and rocker board angle, and EMG data for the Medial Gastrocnemius (MG) and Tibialis Anterior (TA) muscles for the right leg (active leg). We analyze the trends in various postur-ography, kinematic, and muscle-firing parameters while taking reference from simulation analysis todraw insights about the nature of changes in the intermittent control strategy with practice. Result: Multi-modal or skewed histograms of COP, power law in power spectrum, and 2-slope diffu-sion stabilogram are observed in all data. Total kernel density of the peaks in the COP histogramsincrease with practice trials and increases with decrease in intermittent threshold during simulation.The low-frequency slope sL of the ankle angle power spectrum decreases with practice and decreaseswith decrease in intermittency threshold in simulations. Average Energy AE and Simple SquareIntegral SSI decrease with practice. Wavelet spectrum of MG and TA muscle EMG show intermit-tent bursts in the signals. Conclusion: The intermittent control strategy is retained throughout the balanc-ing practice on the rocker board. The trends in parameters with practice are bestexplained by a decrease in intermittency threshold in the control strategy with practice.