Brief Communication
Exp. Biol. Med.
Sec. Neuroscience
Volume 250 - 2025 | doi: 10.3389/ebm.2025.10491
This article is part of the IssueExperimental Biology and Medicine Volume 250 Issue 6View all 8 articles
Impact of aging and body mass index on upper extremity motor unit number index and size
- 1University of Houston, Houston, United States
- 2University of Miami, Coral Gables, Florida, United States
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The focus of this study was to evaluate motor unit number and size across the upper extremity in older adults (aged 60+ years) versus young healthy adults (aged 20-30 years). We hypothesized that older adults would have: fewer motor units and increased motor unit size as compared to young healthy adults (H1), that motor unit size would differ across the upper extremity muscles as compared to young healthy adults (H2), and higher body mass index (BMI) would be associated with lower motor unit numbers (H3).Compound muscle action potential (CMAP), motor unit number index (MUNIX), and motor unit size index (MUSIX) were evaluated in five muscles of the upper extremity. Group differences in CMAP due to aging were accounted for by increased body mass index (BMI); group differences in MUSIX were not impacted by BMI. No difference in MUNIX was found; however, an influence of BMI was found across groups. While this data provides supporting evidence of age-related motor unit changes, body composition changes with age may confound these conclusions when surface electromyography is utilized as the measurement modality. Adiposity estimation should be considered in future EMG studies, particularly in populations with higher BMI values.
Keywords: motor unit loss, Adiposity, neuromuscular, MUNIX, MUSIX
Received: 04 Jan 2025; Accepted: 30 Jun 2025.
Copyright: © 2025 Gorniak, Gulley Cox, Dias, Zhang and Zhang. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.
* Correspondence: Stacey L Gorniak, University of Houston, Houston, United States
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