Background: In recent years there has been a growing effort to develop definitions and algorithms for defining both the age-related loss of muscle strength as well as the age-related loss of muscle mass. The term sarcopenia has become synonymous with the age-related loss of muscle mass— and at times has also been defined as the age-related loss of muscle strength. We have recently argued that the age-related loss of muscle strength is only partially explained by the reduction in muscle mass, and that other physiologic factors explain muscle weakness in older adults. Accordingly, we recently proposed that these two events (strength loss and mass loss) need to be defined independently. We have previously coined the term ‘dynapenia’ to describe the age-related loss of muscle strength.

The editors of the Journals of Gerontology: Biological and Medical Sciences recently invited us to write an update on our aforementioned article on dynapenia. In our upcoming manuscript we will propose a working decision algorithm to define dynapenia.

Working decision algorithm: Our central theme to this algorithm is that risk factors and screening exams are evaluated within the context of muscle weakness similar to that found in cardiovascular disease and diabetes. We felt a screening grip strength test and assessment of risk factors could be used in a complementary fashion. An individual with few risk factors and normal grip strength would “pass” screening and not be considered to have or be at elevated risk for dynapenia. Individuals with few risk factors but low grip strength— or high risk factors alone— would be referred for an advanced test assessing knee extensor maximal strength. We recognize that clinically relevant cut points of grip and knee extensor strength have yet to be fully characterized and developed. However, it is anticipated that these issues will be resolved with future studies. We should also note, that the algorithm illustrates the potential for additional testing on the etiology of dynapenia.

For more information on our prior work please see: 
http://www.ncbi.nlm.nih.gov/pubmed/18772470
http://www.ncbi.nlm.nih.gov/pubmed/20154609

Solicitation for Input: There is insufficient evidence in the literature to identify specific cut points, fully evaluate risk factors, and developed a final algorithm. However, we do wish to propose an early stage algorithm to encourage discussion along this line, and we would like to solicit your input on this algorithm (algorithm is shown above). Specifically, we would be grateful if you would vote on topic listed on the right side of the blog and provide comments as you see fit.

We thank you for your time and input on this matter.

Sincerely,

Todd Manini, Ph.D.                   Brian Clark, Ph.D.
University of Florida                 Ohio University
tmanini@aging.ufl.edu            clarkb2@ohio.edu

Disclaimer: The comments and results associated with this blog are available to the public and may be used in future presentations and publications.