## 1 Introduction  
The loss of muscle mass is a gradual process that begins in early adulthood and accelerates with age. [PERSON] et al. [1] reported a loss of approximately 1-2% per year after age 30 and 2-3% per year after age 60. Furthermore, the rate of loss increases with age. The loss of muscle mass due to aging can result in a reduction in muscle strength, gait speed, and balance, which may subsequently lead to a decline in physical activity and the development of conditions [2; 3]. This decline in physical function may contribute to the development of various diseases [4; 5]. It is possible that mitochondrial dysfunction, chronic inflammation and neuromuscular damage may be involved in the loss of muscle and the precise mechanisms of muscle synthesis remain unclear [6; 7; 8]. Nutritional factors, including reduced physical activity and insufficient protein intake, have the potential to impede muscle synthesis [9; 10]. Furthermore, muscle degradation factors, such as muscle RING finger-1 (MuRF-1) and atropin-1, and muscle synthesis factors, including myoblast determination protein (MyoD) and myogenin, are associated with muscle degradation, although individual differences remain [11; 12]. Skeletal muscle serves as a health marker, influencing the body's capacity to maintain and perform activities. Skeletal muscle mass is maintained by an equilibrium between muscle protein breakdown and synthesis. When this equilibrium is disrupted, skeletal muscle mass decreases [13; 14]. A reduction in skeletal muscle mass is associated with a decline in exercise capacity, which in turn results in a reduction in physical activity performance [15]. [PERSON] et al. [16] demonstrated that a diet with high protein intake is an effective method for increasing skeletal muscle mass. Conversely, individuals who consumed protein below the recommended intake level had significantly reduced skeletal muscle mass and strength. Tenebrio molitor L. is the larva of Tenebrio molitor, which belongs to the beetle family Tenebrionidae and is commonly referred to as the mealworm [17]. Mealworms are used as food in many countries, including the United States, Belgium, the Netherlands, France, the United Kingdom, China, Thailand, Japan, and Canada, because of their capacity for mass rearing and efficient production [18]. In Korea, the Ministry of Food and Drug Safety has recognized mealworms as edible food since 2016. Furthermore, mealworms have considerable potential as a food ingredient capable of providing a high-quality protein source [19]. However, mealworms have a high fat content, which can result in quality changes owing to rancidity and poor storage [20]. To address these issues, mealworms are typically defatted and pulverized, and most mealworms employed in the food industry are distributed and utilized as defatted mealworm powder (DMP) [21; 22]. DMP is a rich source of essential amino acids necessary for muscle synthesis, including branched-chain amino acids (BCAAs) [23]. BCAAs, which consist of essential amino acids, such as leucine, isoleucine, and valine, serve as precursors for muscle protein synthesis [24]. Moreover, studies conducted on rats have indicated that the oral administration of BCAAs can facilitate the expression of mRNAs linked to muscle protein synthesis, including myogenin. [25; 26; 27]. Enzymatic protein hydrolysis has been extensively employed in the food industry as a means of more effectively utilizing protein materials [28]. The cleavage sites on raw proteins vary depending on the type of protein-hydrolyzing enzyme used, resulting in various potential final products [29]. Enzymes can be classified into two main categories: exopeptidases and endopeptidases. Based on the manner in which they act on the substrate, these enzymes can be classified as either exopeptidases, which act on the N-terminal \(\alpha\)-amino group, or endopeptidases, which act on peptide bonds within the protein [30].