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Effect of Anodal Transcranial Direct Current Stimulation of the Motor Cortex on Elbow Flexor Muscle Strength in the Very Old

Oki, Kentaro PhD1; Clark, Leatha A. DPT, MS1; Amano, Shinichi PhD1,2; Clark, Brian C. PhD1,3,4

Journal of Geriatric Physical Therapy: October/December 2019 - Volume 42 - Issue 4 - p 243–248
doi: 10.1519/JPT.0000000000000145
Research Reports
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Background and Purpose: Muscle weakness predisposes older adults to a fourfold increase in functional limitations and has previously been associated with reduced motor cortex excitability in aging adults. The purpose of this study was to determine whether a single session of anodal transcranial direct current stimulation (tDCS) of the motor cortex would increase elbow flexion muscle strength and electromyographic (EMG) amplitude in very old individuals.

Methods: Eleven very old individuals—85.8 (4.3) years—performed 3 maximal isometric elbow flexion contractions before and after 20 minutes of sham or anodal tDCS on different days. Order of stimulation was randomized, and the study participants and investigators were blinded to condition. In addition, voluntary activation capacity of the elbow flexors was determined by comparing voluntary and electrically evoked forces.

Results: Anodal tDCS did not alter muscle strength or EMG activity in comparison to sham stimulation. Elbow flexion voluntary activation capacity was very high among the study participants: 99.3% (1.8%).

Conclusion: Contrary to our hypothesis, we observed no effect of anodal tDCS and no impairment in elbow flexor voluntary activation capacity in the very old. Whether anodal tDCS would exert a positive effect and support our initial hypothesis in another muscle group that does exhibit impairments in voluntary activation in older adults is a question that is still to be addressed.

1Ohio Musculoskeletal and Neurological Institute, Ohio University, Athens.

2Clinical and Translational Research Unit, Ohio University, Athens.

3Department of Biomedical Sciences, Ohio University, Athens.

4Department of Geriatric Medicine, Ohio University, Athens.

Address Correspondence to: Brian C. Clark, PhD, Ohio Musculoskeletal and Neurological Institute, Ohio University, 250 Irvine Hall, Athens, OH 45701 (clarkb2@ohio.edu).

Research reported in this publication was supported by the National Institute on Aging of the National Institutes of Health under Award Number R01AG044424. The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.

The authors declare no conflicts of interest.

Richard Bohannon was the Decision Editor.

© 2019 Academy of Geriatric Physical Therapy, APTA
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