Why does strength diminuish with aging?

9 min

‍After 30-40 years, we all tend to lose muscle mass. Up to the age of 60, it is estimated that this process leads to losing about 0.25 kg of muscle per year and putting on 0.5 kg of fat in the same period. Overall, during three decades we may lose 7.5 kg of lean mass, while gaining 15 kg of fat mass on average.

Along 30 years we lose 7.5 kg of lean mass and gain 15 kg of fat mass, on average

Although muscle decline is an aspect of the normal aging process, in some people it manifests itself more rapidly or accentuated, leading to the development of a clinical condition called sarcopenia (from the Greek sarx, i.e. meat, and penia, i.e. deficiency).

The term was coined in the late 1980s by Irwin Rosenberg, then director of the Jean Mayer USDA Human Nutrition Research Center on Aging at Tufts University School of Medicine, with the aim of drawing attention to and stimulating research into one of the most obvious and dramatic processes of ageing, an important risk factor for functional loss in older people.

In 2016 the World Health Organization recognized sarcopenia as a disease.

Preserving muscle mass and its function decreases the likelihood of falls and allows you to maintain your own independence for longer time.

Sarcopenia is a physiological phenomenon that can reach pathological levels however, and. when it does, it may reduce the quality of life and predispose to disability. Preserving the muscular mass and functions decreases the likelyhood of falls and allows the maintainance of independence for longer time, while lowering the family expenditures. It also has an impact on the National Health Systems, given its high prevalence in the elderly.

Handgrip strength and appendicular lean mass: these are the measures of strength and muscle mass that currently best predict the onset of functional limitations.

Muscle: quantity but above all quality

Muscle mass and its functions are the two parameters for the clinical definition of sarcopenia. For many years the loss of muscle mass was the only parameter to be assessed. Today, the scientific community favours a model that takes into account both the quantity and the quality of the muscle.

The most recent European recommendations tend to attach particular importance to measuring muscle function – such as strength – rather than mass volume.

The most recent European recommendations tend to give particular importance to measuring muscle function – such as strength – rather than mass volume. In the context of a clinical evaluation, the muscle function can be measured quite easily using a dynamometer.

Against the loss of muscle function, typical of aging, exercise is the best medicine: “use it or lose it”, as the Anglo-Saxons say.

Quantifying muscle mass accurately, on the other hand, is a more complicated operation: it would require methods such as nuclear magnetic resonance imaging and computed axial tomography, which can hardly be included into the evaluation process. However, simpler methods can be used, such as double energy X-ray absorbimetry (DXA) or bioimpedance measurement (BIA), which provide an overall estimate of lean mass within the body.

How to measure muscles
Several expert groups met between 2009 and 2012 to better define and measure sarcopenia, including the European Working Group on Sarcopenia in Older People (EWSGOP), which published its model in 2010 and updated it in 2018.

However, there are two parameters that best describe the quality and quantity of muscle: handgrip strength and appendicular lean mass.

Equally important was the work of the Sarcopenia Project carried out by the Biomarkers Consortium of the Foundation for the National Institutes of Health (FNIH). Thanks to the analysis of data from more than 26,000 people collected in nine international cohort studies, the researchers identified two parameters of strength and muscle mass that currently best predict the onset of functional limitations: handgrip strength and appendicular lean mass.

Sarcopenia: how to prevent and slow it down
Having said that, sarcopenia is a complex phenomenon, difficult to isolate from the physiological process of aging that generates it. Moreover, it can hide behind the excess of adipose tissue and, therefore, potentially affect even people with normal body mass.

Physical exercise is the best medicine: “use it or lose it”, as the Anglo-Saxons say.

Many factors influence the loss of muscle, from hormonal and inflammatory ones to some diseases, but a great weight has the lifestyle. Exercise is the best medicine: “use it or lose it”, as the Anglo-Saxons say. Even better if conducted in the open air so that the sun’s rays trigger the production of vitamin D, a hormone probably also involved in maintaining muscle fitness.

The starting conditions make the difference: building a good “biological capital” during the first 30 years of life means being able to count on an insurance for the future.

A balanced diet, like the Mediterranean diet, also plays its part, guaranteeing a sufficient supply of protein, which must be distributed over the different meals of the day.

However, the starting conditions make the difference: building a good biological capital during the first 30 years of life, both from a qualitative and quantitative point of view, means being able to count on insurance for the future, because it is in the later years that the muscle decline will start. Following a healthy lifestyle from an early age therefore allows us to delay functional loss while aging.

There are no drugs for sarcopenia to date, but preliminary studies suggest that correcting some hormonal imbalances – such as testosterone deficiency in men – or intervening on particular mechanisms that regulate muscle functions – such as myostatin inhibitors – could lead to the development of drugs and offer benefits especially to those who, for health or social reasons, are unable to lead an optimal lifestyle.

References

Nature 555, S15-S17 (2018) doi: 10.1038/d41586-018-02479-z (Nature Outlook: The future of medicine, an editorially independent supplement produced with the financial support of third parties.)https://www.nature.com/articles/d41586-018-02479-z

Rosenberg I. Sarcopenia: origins and clinical relevance. J Nutr. 1997;127(5 Suppl):990S-991S.

Landi F, Calvani R, Cesari M, et al. Sarcopenia as the Biological Substrate of Physical Frailty. Clin Geriatr Med. 2015;31(3):367-374. doi:10.1016/j.cger.2015.04.005.

Forbes G. Longitudinal changes in adult fat-free mass: influence of body weight. Am J Clin Nutr. 1999;70(6):1025-1031.

Cruz-Jentoft A, Baeyens J, Bauer J, et al. Sarcopenia: European consensus on definition and diagnosis: Report of the European Working Group on Sarcopenia in Older People. Age Ageing. 2010;39(4):412-423. doi:10.1093/ageing/afq034.

Cruz-Jentoft A, Bahat G, Bauer J, et al. Sarcopenia: revised European consensus on definition and diagnosis. Age Ageing. 2019;48:16-31.

Cao L, Morley JE. Sarcopenia Is Recognized as an Independent Condition by an International Classification of Disease, Tenth Revision, Clinical Modification (ICD-10-CM) Code. J Am Med Dir Assoc. 2016;17(8):675-677. doi:10.1016/j.jamda.2016.06.001.


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