Neuromuscular contributions to age-related weakness

Authors: CLARK, DAVID - University Of Florida; FIELDING, ROGER - Jean Mayer Human Nutrition Research Center On Aging At Tufts University

Submitted to: Journal of Gerontology Medical Science
Publication Type: Review Article
Publication Acceptance Date: 2/10/2011
Publication Date: 1/1/2012
Citation: Clark, D.J., Fielding, R.A. 2012. Neuromuscular contributions to age-related weakness. Journal of Gerontology Medical Science. 67(1):41-47.

Interpretive Summary:

Technical Abstract: Age-related physiological change of neuromuscular function is not a linear process and is likely influenced by various biological and behavioral factors (e.g., genetics, nutrition, physical activity level, comorbidities, etc.). These factors contribute to heterogeneity among older adults, which challenges the ability to understand what neuromuscular deficits are inherent to aging. To minimize the confounding effects of this heterogeneity, investigators should carefully control and report the characteristics of their research participants. Of the relevant articles cited in this review, approximately 70% reported performing a medical screening (beyond reporting absence of neuromuscular disease), 63% reported specific screening criteria for physical activity levels or actually recorded physical activity, 52% provided information on body composition, and 11% administered a functional assessment. It is possible that some studies performed these procedures but omitted the details from the published article. Our recent work shows that administering a functional assessment can be valuable for identifying older individuals with higher and lower neuromuscular function. We categorized healthy community-dwelling older adults into two groups based primarily on Short Physical Performance Battery score (=10 vs. =9 points, out of 12 maximum points). The lower functioning group exhibited marked weakness and impaired agonist activation compared with the higher functioning group (17,36). This finding suggests that an activation deficit may contribute to emerging declines in mobility function. Yet in most studies, it is likely that the participants in these distinct groups would have been merged into a single heterogeneous older group, thus obscuring potentially valuable insight into the neural determinants of weakness and physical function.