## 1 Introduction  
Sarcopeniaia is a chronic condition that develops during the natural process of aging. However, although its clinical significance has been discussed for a long time, it has recently been officially classified as a disease. In 2016, the USA included sarcopenia in the ICD-10-CM, which is a global classification of diseases published by the World Health Organization, and assigned the disease a specific cod (M62.84) [1]. Sarcopeniaia was also included in the eighth revision of the Korean Classification of Diseases (KCD) and was assigned an ICD-10-CM code (M62.5) [2]. Sarcopeniaia is defined as persistent muscle atrophy characterized by a slow loss of skeletal muscle mass and function, physical disability, poor quality of life, and death [3]. Sarcopeniaia is generally diagnosed by measuring muscle mass, strength, and function. Regular exercise is the best treatment for muscle atrophy [4]. As no drugs have been approved to date, new therapeutic agents must be developed to prevent sarcopenia. Rosemary (_Rosmarius officinalis_ L., Lamiaceae), which is native to the Mediterranean region, has many culinary and medicinal uses. To date, there are more than 20 varieties of rosemary, and the herb has been reported to exert a variety of physiological effects,including the improvement of memory [5], antioxidant status [6], inflammation [7], osteoporosis [8], as well as promoting the differentiation of mesenchymal stem cells into osteoblasts and adipocytes [9] and hypertrophy in human skeletal muscle cells [10]. Rosemary contains a variety of phytochemicals, including rosmarinic acid, carnosol, carnosol, oleanolic acid, and unsolic acid (UA), which itself has been reported to exhibit physiological activities, including cytotoxicity to tumor cells [11], anticancer effects [12], and hypouricemic [13]. Many research results have been reported on the effects of various phytochemicals in rosmary on skeletal muscle cells. Rosemarinic acid increases glucose uptake in skeletal muscle cells and activates 5\({}^{\prime}\)-adenosine monophosphate-activated protein kinase (AMPK) [14]. Carnosol attenuated C2C12 myotube atrophy induced by tumor-derived exosomal miR-183-5p via inhibition of Smad3 pathway activation and maintenance of mitochondrial respiration [15]. Carnosol acid weakens insulin resistance induced by free fatty acids in muscle cells and adipocytes [16]. Ursolic acid ameliorates indoxyl sulfate-induced disorder of mitochondrial biogenesis in C2C12 cells [17]. Together, UA and leucine have been reported to potentiate the differentiation of C2C12 murine myoblasts through the mTOR signaling pathway [18]. Indeed, an ethanol extract of loquat (_Eriobotrya japonica_), which contained UA, was reported to prevent dexamethasone-induced muscle atrophy by inhibiting the muscle degradation pathway in Sprague Dawley rats [19], and loquat leaf extract has been reported to enhance both myogenic differentiation and muscle function in aged Sprague Dawley rats [20] and healthy human adults [21]. Therefore, it is necessary to study the inhibitory effects of ethanolic rosmary extracts on sarcopenia. Skeletal muscle differentiation is a strictly regulated process involving the specification of mesodermal precursors in myoblasts and subsequent differentiation and fusion into multinucleated myotubes. During the process of muscle differentiation, myogenic regulatory factors (MRFs), including the basic helix-loop-helix (bHLH) transcription factors MyoD, Myf5, myogenin, and MRF4, play important roles in muscle formation [21]. In particular, MyoD is essential to the formation of skeletal muscle and plays unique roles in the development of epaxial and hypaxial muscle [22; 23; 24]. AMPK is an energy-sensing and signaling protein that, when activated, increases ATP production by stimulating glucose uptake and fatty acid oxidation and simultaneously inhibits ATP-consuming processes such as protein synthesis.