Sarcopenia

Sarcopenia is the progressive loss of skeletal muscle strength and mass, often accompanied by reduced physical performance. It is associated with aging but can also arise from disease, inactivity, or inadequate nutrition.

Muscle protein synthesis: The cellular process that builds proteins from amino acids, including proteins used in skeletal muscle. Sarcopenia develops when muscle protein building fails to keep pace with breakdown.
Handgrip strength: The maximum force a person can exert while squeezing a handheld dynamometer. Low grip strength is a practical indicator used to identify probable sarcopenia.
Irwin Rosenberg: A physician and researcher who introduced the term sarcopenia in 1989. Rosenberg named the age-related loss of muscle mass that the concept originally described.
Cachexia: A disease-associated syndrome of involuntary weight loss, muscle wasting, and often systemic inflammation. Cachexia is driven by underlying illness and differs from sarcopenia in its typical causes and clinical context.
Muscle protein breakdown: The cellular degradation of muscle proteins, which supplies amino acids and removes damaged proteins. Accelerated breakdown can contribute to the net muscle loss seen in sarcopenia.
Chair stand test: A timed test measuring how quickly a person repeatedly rises from a chair without using the arms. The test assesses lower-body strength relevant to sarcopenia screening.
European Working Group on Sarcopenia in Older People: A European expert group that developed influential clinical definitions and diagnostic guidance for sarcopenia. Its 2010 consensus helped establish operational criteria for identifying the condition.
Frailty: A state of increased vulnerability to stressors caused by reduced physiological reserve across multiple systems. Frailty includes broader functional vulnerability, whereas sarcopenia specifically concerns skeletal muscle.
Motor unit: A motor neuron and all the muscle fibers it activates. Age-related loss and remodeling of motor units can weaken muscle independently of mass.
Gait speed: The rate at which a person walks over a measured distance. Slow gait can indicate impaired physical performance in people with sarcopenia.

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