Trained muscles age differently at the molecular level

Researchers from Amsterdam UMC and Maastricht University compared muscle tissue from four groups: young adults, normally active older adults, trained older adults, and physically impaired older adults. The key was the study design: the young and the normally active older participants took a similar number of daily steps on average. This allowed the team to separate what ageing does from what inactivity does.

The study, published in Nature Aging, measured gene expression, metabolites, and fat content in muscle biopsies. In older untrained participants, genes involved in mitochondrial function (the cell’s energy-producing machinery) were clearly less active. NAD+, a molecule essential for energy metabolism and cellular repair, was also reduced. In trained older adults, more than half of those age-related changes in gene activity were absent.

Training versus being active: a crucial distinction

‘Trained’ in this context meant at least three planned one-hour exercise sessions per week for more than a year. People who were generally active but did not train this way still showed clear signs of molecular muscle ageing, despite taking a similar number of steps as the young participants.

That is a striking finding. It suggests that the intensity and regularity of exercise matter, not just total movement. That said, the study is small: 47 participants in total. The findings are promising but need to be confirmed in larger cohorts.

What this means for staying healthy longer

Age-related muscle loss, known as sarcopenia, increases the risk of falls, disability, and premature death. If structured training can substantially slow the molecular ageing of muscle, that is a strong argument for preventive exercise that goes beyond general activity guidelines. The study provides a molecular basis for something already suspected clinically: those who genuinely train retain younger muscles.

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