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Author Notes:

Correspondence: Winston Byblow, Movement Neuroscience Laboratory, Department of Sport and Exercise Science, The University of Auckland, Private Bag 92019, Auckland 1142, New Zealand. Tel: +64 9 373 7599 x 86844 Fax: +64 9 373 7043 E‐mail: w.byblow@auckland.ac.nz

The authors wish to thank April Ren and Jennifer Chin for their assistance with data collection. The SaeboMAS device was generously provided by Henry Hoffman at Saebo Incorporated.

Conflict of Interest: None declared

Subjects:

Research Funding:

This research was supported by a University of Auckland FRDF grant to WB.

KR was supported by a University of Auckland Doctoral Scholarship.

Keywords:

  • Gravity compensation
  • integrated control
  • intracortical inhibition
  • motor cortex
  • transcranial magnetic stimulation

Partial weight support differentially affects corticomotor excitability across muscles of the upper limb

Tools:

Journal Title:

Physiological Reports

Volume:

Volume 2, Number 12

Publisher:

, Pages e12183-e12183

Type of Work:

Article | Final Publisher PDF

Abstract:

Partial weight support may hold promise as a therapeutic adjuvant during rehabilitation after stroke by providing a permissive environment for reducing the expression of abnormal muscle synergies that cause upper limb impairment. We explored the neurophysiological effects of upper limb weight support in 13 healthy young adults by measuring motor-evoked potentials (MEPs) from transcranial magnetic stimulation (TMS) of primary motor cortex and electromyography from anterior deltoid (AD), biceps brachii (BB), extensor carpi radialis (ECR), and first dorsal interosseous (FDI). Five levels of weight support, varying from none to full, were provided to the arm using a commercial device (Saebo Mobile Arm Support). For each level of support, stimulus–response (SR) curves were derived from MEPs across a range of TMS intensities. Weight support affected background EMG activity in each of the four muscles examined (P < 0.0001 for each muscle). Tonic background activity was primarily reduced in the AD. Weight support had a differential effect on the size of MEPs across muscles. After curve fitting, the SR plateau for ECR increased at the lowest support level (P = 0.004). For FDI, the SR plateau increased at the highest support level (P = 0.0003). These results indicate that weight support of the proximal upper limb modulates corticomotor excitability across the forearm and hand. The findings support a model of integrated control of the upper limb and may inform the use of weight support in clinical settings.

Copyright information:

© 2014 The Authors

This is an Open Access work distributed under the terms of the Creative Commons Attribution 4.0 International License (https://creativecommons.org/licenses/by/4.0/).
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