Title: Muscle activation patterns in healthy subjects and stroke survivors in an unpredictable robotic environment

Authors: Mukul Mukherjee; Wen Liu

Addresses: Nebraska Biomechanics Core Facility, University of Nebraska at Omaha, 6001 Dodge Street, Omaha, Nebraska-68182, USA. ' Department Physical Therapy and Rehabilitation Science, University of Kansas Medical Centre, 3901 Rainbow Blvd., Kansas City, Kansas-66160, USA

Abstract: The purpose of this study was to describe muscle activity changes during learning of reaching movements in unpredictable dynamic environments. Healthy subjects and stroke survivors performed reaching tasks with a robotic manipulandum in a force field whose magnitude was randomised. In healthy subjects, electromyographic (EMG) activity of the biceps, triceps, anterior and posterior deltoid showed an effect of training on EMG onset time, peak onset time and integrated EMG. Differences in EMG tuning effects were also observed with training. In stroke survivors, only the biceps muscle showed reduction in EMG onset. Moreover, distinct target direction effects were noted. Differences in EMG tuning effects with training were conserved after stroke. In an unpredictable dynamic environment, healthy human subjects demonstrate motor adaptation by reducing their EMG onset times and stabilising the EMG directional effect of dynamic training. These characteristic effects are compromised albeit present in stroke survivors.

Keywords: stochastic; random force fields; robot manipulators; motor adaptation; upper limbs; muscle activation patterns; healthy subjects; stroke survivors; muscle activity; reaching movements; learning; muscle training; unpredictable environments; dynamic environments; electromyographs; EMG.

DOI: 10.1504/IJMA.2012.046582

International Journal of Mechatronics and Automation, 2012 Vol.2 No.1, pp.1 - 14

Available online: 01 May 2012 *

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