Skeletal muscles, which are involved in the execution of many metabolic, mechanical and biological functions of the body, contribute to energy consumption, movement and healing processes. Muscles play a critical role in glucose metabolism, energy homeostasis, circulatory regulation and control of metabolic gene expression. In addition, muscles interact with the endocrine system by secreting myokines and contribute to the metabolic balance with organs such as adipose tissue, liver and pancreas through this mechanism. Age, nutrition and physical activity level have a direct effect on muscle mass. Factors such as aging, insufficient physical activity and poor nutrition can lead to a decrease in muscle mass, which can lead to problems such as insulin resistance, obesity and metabolic disorders. Resistance exercises and aerobic activities are of great importance for maintaining muscle mass. Resistance exercises contribute to hypertrophy and functional recovery by increasing protein synthesis. Aerobic exercises reduce muscle loss in the long term and support energy metabolism. Adequate and high quality protein intake is necessary for these exercises to be effective and for muscle reconstruction and repair. When determining the protein requirement, the effect of protein quality and biological value on body protein should be considered. In athlete nutrition, the right type, amount and timing of protein are important to optimise muscle protein synthesis. Especially in the post-exercise period, protein intake accelerates muscle growth. In addition, carbohydrates are also important as an energy source for athletes, and proper carbohydrate intake as well as protein intake plays a critical role in terms of muscle mass maintenance and meeting energy requirements. The correct timing of these factors contributes to performance enhancement and muscle gain. Protein synthesis is regulated by IGF-1 and mTOR signalling pathways, while it is important to control factors that increase protein degradation such as myostatin.  Rest, especially sleep, is essential for maintenance of muscle protein synthesis and recovery. Pre-sleep protein intake has been scientifically proven to support muscle building. Especially in elderly individuals, the recovery provided by protein intake before sleep can prevent muscle loss.  Balanced management of exercise, nutrition and rest is an indispensable strategy for muscle health and overall physical endurance.