Osteoporosis International

, Volume 21, Issue 4, pp 543-559

First online:

Open Access This content is freely available online to anyone, anywhere at any time.

Sarcopenia: etiology, clinical consequences, intervention, and assessment

  • T. LangAffiliated withDepartment of Radiology and Biomedical Imaging, UCSF/UCB Joint Bioengineering Graduate Group, University of California Email author 
  • , T. StreeperAffiliated withDepartment of Radiology and Biomedical Imaging, University of California
  • , P. CawthonAffiliated withCalifornia Pacific Medical Center Research Institute
  • , K. BaldwinAffiliated withPhysiology and Biophysics, University of California
  • , D. R. TaaffeAffiliated withSchool of Human Movement Studies, The University of Queensland
  • , T. B. HarrisAffiliated withLaboratory of Epidemiology and Biometry, Intramural Research Program, National Institute on Aging


The aging process is associated with loss of muscle mass and strength and decline in physical functioning. The term sarcopenia is primarily defined as low level of muscle mass resulting from age-related muscle loss, but its definition is often broadened to include the underlying cellular processes involved in skeletal muscle loss as well as their clinical manifestations. The underlying cellular changes involve weakening of factors promoting muscle anabolism and increased expression of inflammatory factors and other agents which contribute to skeletal muscle catabolism. At the cellular level, these molecular processes are manifested in a loss of muscle fiber cross-sectional area, loss of innervation, and adaptive changes in the proportions of slow and fast motor units in muscle tissue. Ultimately, these alterations translate to bulk changes in muscle mass, strength, and function which lead to reduced physical performance, disability, increased risk of fall-related injury, and, often, frailty. In this review, we summarize current understanding of the mechanisms underlying sarcopenia and age-related changes in muscle tissue morphology and function. We also discuss the resulting long-term outcomes in terms of loss of function, which causes increased risk of musculoskeletal injuries and other morbidities, leading to frailty and loss of independence.


Aging Falls Imaging Muscle strength Sarcopenia Skeletal muscle