The term 'sarcopenia’ was coined by Irwin Rosenberg as age-related 'loss of skeletal muscle mass in Greek’. Although several diagnostic criteria of sarcopenia have been proposed by several academic societies in Europe, Asia, and the United States of America, most of them have been found to show similar prognostic ability for incident disability and mortality. The diagnostic criteria of sarcopenia include muscle weakness and / or muscle function in addition to low skeletal muscle mass because longitudinal studies indicated that skeletal muscle mass was correlated with muscle strength less than expected, and that muscle weakness affected more on disability than loss of skeletal muscle mass. It is important how we implement the diagnosis of sarcopenia into daily practice and how we manage sarcopenia based on the diagnosis. Research updates on sarcopenia are described in this article.