Myofibrillar refers to the structural components of muscle fibers, specifically the myofibrils, which are long, thread-like proteins responsible for muscle contraction. These myofibrils are made up of repeating units called sarcomeres, which contain the proteins actin and myosin. The interaction between these proteins allows muscles to contract and generate force. In addition to their role in muscle contraction, myofibrillar proteins are important for muscle growth and repair. When muscles are exercised, especially during resistance training, myofibrillar proteins undergo stress, leading to micro-tears. This process stimulates muscle adaptation and growth, making myofibrillar proteins essential for athletes and fitness enthusiasts.