Final answer:
Fast twitch type II muscle fibers fatigue quickly and have a lower aerobic capacity, which restricts endurance and may lead to delayed onset muscle soreness due to their limited oxygen delivery and reliance on anaerobic metabolism.
Step-by-step explanation:
Two negative aspects of fast twitch type II muscle fibers are that they fatigue rapidly and have less aerobic capacity. Because these fibers primarily generate energy through anaerobic glycolysis, they produce energy less efficiently than slow-twitch fibers, leading to quicker exhaustion during sustained activities.
Another downside is their lower density of mitochondria and capillaries as well as reduced myoglobin content, which limits their oxygen-carrying capacity and endurance compared to slow-twitch type I muscle fibers. Despite their ability to contract with great force and speed, making them essential for explosive movements like sprinting or weight lifting, their rapid fatigue rate is a considerable disadvantage for endurance-related activities.
Moreover, this rapid and powerful contraction can lead to increased occurrences of delayed onset muscle soreness (DOMS) as a result of microscopic tears in the muscle fibers from high-intensity, anaerobic workouts.