Muscle fibers are classified into different types based on their contractile properties and metabolic capacities. Slow-twitch muscle fibers (Type I) are more resistant to fatigue and are primarily used for endurance activities. They contain a higher number of mitochondria and myoglobin, which facilitate aerobic respiration. Conversely, Fast-twitch muscle fibers (Type II) are more anaerobic and fatigue faster, making them more suitable for short bursts of high-intensity activity. A decrease in the proportion of Type I fibers or mitochondrial density can impair endurance.
