what is muscle
Muscle is a soft tissue found in most animals. Muscle cells contain protein filaments of actin and myosin that slide past one another, producing a contraction that changes both the length and the shape of the cell.Muscles function to produce force and motion. Type I, slow twitch, or red muscle, is dense with capillaries and is rich in mitochondria and myoglobin, giving the muscle tissue its characteristic red color. 2  It can carry more oxygen and sustain aerobic activity using fats or carbohydrates as fuel.