Which type of muscle fibers are primarily fueled by aerobic metabolism?

The correct answer is associated with slow oxidative fibers, which are primarily fueled by aerobic metabolism. These muscle fibers are designed for endurance and sustained activity, utilizing oxygen to produce ATP efficiently. This capability makes them ideal for prolonged, low to moderate intensity exercises, such as distance running or cycling.

Slow oxidative fibers contain a high number of mitochondria and myoglobin, which enhances their ability to transport and use oxygen. They also have a rich supply of capillaries, contributing to efficient oxygen delivery to the muscle tissue. The reliance on aerobic metabolism allows these fibers to produce energy for extended periods without fatiguing quickly.

While fast oxidative fibers also utilize aerobic metabolism, they are generally more associated with activities that demand both quick bursts of energy and moderate endurance. Fast glycolytic fibers predominantly utilize anaerobic metabolism, favoring short, explosive movements but fatigue rapidly. Intermediate fibers have characteristics of both slow and fast fibers but do not exclusively rely on aerobic metabolism like the slow oxidative fibers do.

Thus, slow oxidative fibers stand out specifically for their primary reliance on aerobic metabolism, which is why this option is correct.