Objective: To study the modifications induced by training of a coordinated movement on the primary motor cortex (M1) maps of one proximal muscle and one distal muscle activated alone and during their co-contraction.
Methods: Six healthy female sport students performed a 6-week training program during which they were trained in darts 3-4 times a week. At the end each subject had made more than 1200 throws. Transcranial magnetic stimulation (TMS) was used to map the proximal medial deltoid (MD) and the distal brachio-radialis (BR) muscle representations on M1. Motor evoked potentials (MEPs) amplitude and excitability curves were used to test corticomotor excitability.
Results: The cortical representation areas of each muscle separately increased after training. The cortical representation and the excitability curve of the BR muscle increased during co-activation with the MD. Combining co-contraction and training produced a further enlargement of the M1 representation of the BR muscle.
Conclusions: The enlargement of the BR representation in M1 suggests the development of overlapping zones specifying functional synergies between distal and proximal muscles.
Significance: Our findings support the idea that training of a coordinated movement involving several muscles and joints requires an activity-dependent coupling of cortical networks.
Copyright © 2010 International Federation of Clinical Neurophysiology. Published by Elsevier Ireland Ltd. All rights reserved.