dynapenia

Dynapenia is the age-related loss of muscle strength that cannot be explained by loss of muscle mass alone. It is characterized by reduced maximal force and power and is a major contributor to impaired mobility and independence in older adults. Dynapenia differs from sarcopenia, which emphasizes decreases in muscle size; individuals may have dynapenia with preserved muscle mass or both conditions.

Epidemiology and impact: The condition becomes more common with advancing age and is influenced by inactivity, chronic disease, inflammation, nutrition, and hormonal changes. Dynapenia is associated with higher rates of falls, disability, hospitalization, and reduced quality of life.

Causes and physiology: Multiple factors contribute, including neural changes such as motor neuron loss and impaired neuromuscular transmission, altered motor unit recruitment, and decreased muscle quality with fat and connective tissue infiltration. Systemic factors like insufficient protein intake, insulin resistance, and chronic inflammation, together with disuse, often drive the strength deficit.

Diagnosis: Dynapenia is assessed primarily through strength testing rather than muscle size. Handgrip dynamometry and lower-extremity tests such as chair rises are commonly used; thresholds are age- and sex-adjusted. Clinicians diagnose dynapenia when strength is reduced beyond what would be expected from preserved muscle mass.

Management and prevention: The most effective intervention is progressive resistance training to increase strength and functional performance, often combined with balance and aerobic activity. Adequate protein and overall nutrition, management of comorbidities, and medication review support improvements and prevention of further decline.

Research and outlook: Ongoing work seeks to clarify mechanisms, refine diagnostic criteria, and explore pharmacologic approaches, though exercise remains the central treatment for dynapenia.

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