The macronutrient primarily responsible for muscle growth and repair is protein. Proteins are made up of amino acids, which are crucial for the body’s ability to rebuild and repair tissues after exercise, particularly strength training. Consuming adequate protein supports muscle recovery and stimulates muscle protein synthesis, helping to enhance overall muscle mass. Athletes and individuals engaging in regular resistance training should aim for a sufficient intake of high-quality protein sources, such as lean meats, dairy, legumes, and plant-based proteins, to optimize their training outcomes.