Research
Mixed
Age-related muscle atrophy is primarily driven by the loss of muscle fibers and motor units starting around age 50, rather than just the shrinking of existing fibers, and this process is largely independent of physical activity levels.
Understanding that muscle loss is partly due to losing entire muscle fibers (not just shrinking them) helps explain why maintaining muscle mass becomes harder with age. While you can't easily replace lost fibers, you can maximize the size and function of the fibers you have through regular exercise.
StrongSupportsHIGH confidence
A gradual loss of muscle fibres begins at approximately 50 years of age and continues such that by 80 years of age, approximately 50% of the fibres are lost from the limb muscles that have been studied... The degree of atrophy of the fibres that remain is largely dependent on the habitual level of physical activity of the individual.
Why this rating
Based on direct counts of muscle fibers in human studies.
Source
AGE‐RELATED CHANGES IN THE STRUCTURE AND FUNCTION OF SKELETAL MUSCLES
John A. Faulkner et al. · Clinical and Experimental Pharmacology and Physiology · 2007
narrative_reviewCited 750×
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