Question

When training for a marathon, some muscle fibers will switch from being fast glycolytic to slow oxidative. If we could biopsy the muscles before and after training and do a histological study, we would find that after training

a. there were more fibers with Type I Myosin ATPas
b. there were fewer fibers with a high concentration of succinate dehydrogenase
c. there were more fibers with Type II myosin ATPase
d. there were fewer fibers with a high concentration of mitochondria

Answer 1

After training for a marathon, muscles adapt by increasing the presence of Type I Myosin ATPase in muscle fibers, as these fibers switch from fast glycolytic to slow oxidative to support more efficient and prolonged aerobic respiration. The correct answer is option A.

Step-by-step explanation:

When training for a marathon, some muscle fibers will switch from being fast glycolytic to slow oxidative. If we were to biopsy the muscles before and after training and do a histological study, we would find that after training:

• there were more fibers with Type I Myosin ATPase

This occurs because endurance training such as marathon running prompts an adaptation in muscle fibers to support more efficient and sustained aerobic respiration. Consequently, these fibers will have increased amounts of mitochondria, myoglobin, and capillary networks to enhance oxygen supply and utilization, and ATP production through aerobic pathways. Type I Myosin ATPase is a characteristic of slow oxidative fibers, which are optimized for long-duration, low-intensity activities like marathon running.