1 RESEARCH ARTICLE + 4 GRAPHICS – CLICK ON IMAGE TO ENLARGE
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THE CORTEX IS A CRITICAL DETERMINANT OF MUSCLE STRENGTH/WEAKNESS – 2014
Clark BC1, Mahato NK2, Nakazawa M3, Law TD4, Thomas JS5.
DESIGN
– Group 1: 4 wks of wrist-hand immobilization to induce weakness
– Group 2: 4 wks of immobilization, but they also performed mental imagery of strong muscle contractions 5 days/wk
– Group 3: control group
– Mental imagery has been shown to activate several cortical areas that are involved with actual motor behaviors
– Before, immediately after, and 1 wk following immobilization, we measured wrist flexor strength, voluntary activation (VA), and the cortical silent period (SP)
RESULTS
(1) Immobilization decreased strength 45.1 ± 5.0%, impaired VA 23.2 ± 5.8%, and prolonged the SP 13.5 ± 2.6%
(2) Mental imagery training, however, reduced loss of strength and VA by ∼50% (23.8 ± 5.6% and 12.9 ± 3.2% reductions, respectively) and eliminated prolongation of the SP (4.8 ± 2.8% reduction)
(3) Significant associations were observed between the changes in muscle strength and VA and SP
CONCLUSIONS
(1) These findings suggest neurological mechanisms, most likely at the cortical level, contribute significantly to disuse-induced weakness
(2) Regular activation of the cortical regions via imagery reduces weakness and VA by maintaining normal levels of inhibition