What property of red, fast twitch muscle fibers contributes to fatigue resistance?

The property of red, fast twitch muscle fibers that contributes to fatigue resistance is greater mitochondrial numbers. Mitochondria are the powerhouses of the cell, responsible for producing adenosine triphosphate (ATP) through aerobic metabolism. A higher number of mitochondria in muscle fibers facilitates an increased capacity for sustained energy production, allowing these fibers to resist fatigue during prolonged periods of activity.

Red, fast twitch muscle fibers, also known as type IIA fibers, leverage their abundant mitochondria to efficiently utilize oxygen and oxidize fats and carbohydrates for energy, which is vital during extended exercise. This capacity for efficient aerobic metabolism enhances their ability to sustain contractions over longer durations compared to muscle fibers with fewer mitochondria.

In contrast, the other options do not specifically relate to fatigue resistance in the same way. Higher myofibril density is associated with increased contraction force but does not directly influence fatigue resistance. Lower contraction force and slower movement speed are characteristics that do not inherently contribute to the endurance of muscle fibers, and rather reflect differences in fiber type properties among fast and slow twitch muscle fibers.