A skeletal muscle comprises different motor units, each containing slow or fast contracting fibers. Slow fibers possess slow-functioning myosin ATPases, which steadily hydrolyze the ATP and take longer to reach peak tension. These fibers generate ATP via aerobic respiration and are also called slow oxidative fibers. They produce large amounts of ATP and can gradually utilize them for prolonged activities, such as maintaining postures. In contrast, fast fibers are thicker than slow fibers and possess fast-functioning myosin ATPases to support rapid contractions. Based on their source of ATP, fast fibers are categorized into oxidative and glycolytic fibers. Fast oxidative fibers primarily support their contractions using aerobic respiration. However, due to the high energy demands of daily activities like walking, these fibers also rely on their glycogen stores to produce additional ATP through anaerobic glycolysis. In contrast, the fast glycolytic fibers rely exclusively on anaerobic glycolysis for their ATP supply, which releases quick but limited energy. As a result, these fibers are used for short bursts of intense activity like sprinting and weightlifting.