Final answer:
The statement 'Have high myoglobin content' is NOT true for fast glycolytic/Type IIX white muscle fibers, as these fibers have low myoglobin content due to their reliance on anaerobic metabolism for quick energy generation, resulting in rapid fatigue and the requirement for high glycogen.
Step-by-step explanation:
The question is asking which of the following is NOT true of fast glycolytic/Type IIX white muscle fibers. To answer this, we need to look at the properties of these muscle fibers. Fast glycolytic fibers, also known as FG fibers or Type IIX fibers, are characterized by several features:
- Fatigue quickly: They are capable of generating a lot of power but are not able to sustain contractions for long periods of time because they fatigue rapidly.
- Generate ATP rapidly: Due to their reliance on anaerobic glycolysis and high glycogen content, these fibers can produce ATP very quickly to facilitate rapid, powerful movements.
- Low myoglobin content: Since FG fibers are not designed for prolonged aerobic activity, they have lower amounts of myoglobin and fewer mitochondria compared to slow-twitch fibers.
Therefore, the statement "Have high myoglobin content" is NOT true of fast glycolytic/Type IIX white muscle fibers. Myoglobin content is higher in slow-twitch (oxidative) fibers that are adapted for continuous, aerobic activities and require a steady supply of oxygen.