2014/10/02 by Brian C. Clark, Niladri Kumar Mahato, Niladri K. Mahato +4 · 124 citations
Engineering · Medicine · Neuroscience · Psychology · #Anatomy #Biology #Cognitive psychology #Communication #Cortex (anatomy) #Medicine #Motor Control and Adaptation #Motor cortex #Muscle activation and electromyography studies #Muscle weakness #Neuroscience #Physical medicine and rehabilitation #Physics #Power (physics) #Psychology #Stimulation #Transcranial Magnetic Stimulation Studies #Weakness
paper · open access · doi:10.1152/jn.00386.2014
published in Journal of Neurophysiology 112(12), 3219-3226 (American Physiological Society)
openalex publication_date 2014/10/02 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/01
We tested the hypothesis that the nervous system, and the cortex in particular, is a critical determinant of muscle strength/weakness and that a high level of corticospinal inhibition is an important neurophysiological factor regulating force generation. A group of healthy individuals underwent 4 wk of wrist-hand immobilization to induce weakness. Another group also underwent 4 wk of immobilization, but they also performed mental imagery of strong muscle contractions 5 days/wk. Mental imagery has been shown to activate several cortical areas that are involved with actual motor behaviors, including premotor and M1 regions. A control group, who underwent no interventions, also participated in this study. Before, immediately after, and 1 wk following immobilization, we measured wrist flexor strength, voluntary activation (VA), and the cortical silent period (SP; a measure that reflect corticospinal inhibition quantified via transcranial magnetic stimulation). Immobilization decreased strength 45.1 ± 5.0%, impaired VA 23.2 ± 5.8%, and prolonged the SP 13.5 ± 2.6%. Mental imagery training, however, attenuated the 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). Significant associations were observed between the changes in muscle strength and VA (r = 0.56) and SP (r = -0.39). These findings suggest neurological mechanisms, most likely at the cortical level, contribute significantly to disuse-induced weakness, and that regular activation of the cortical regions via imagery attenuates weakness and VA by maintaining normal levels of inhibition.