Which muscle fiber type has high resistance to fatigue and low contraction speed?

Type I muscle fibers, also known as slow-twitch fibers, are characterized by their high resistance to fatigue and lower contraction speed compared to other fiber types. These fibers are designed for endurance activities and are highly efficient at using oxygen to generate ATP through aerobic metabolism, allowing them to sustain prolonged periods of activity without fatiguing quickly.

Due to their rich supply of mitochondria and myoglobin, Type I fibers excel in activities that require sustained muscle contractions, such as long-distance running, cycling, or any other form of aerobic exercise. Their slow contraction speed is well-suited for these endurance activities, as they do not require the rapid, powerful bursts of energy that other fiber types provide.

In contrast, Type IIa fibers are fast-twitch fibers that have a moderate resistance to fatigue and a quicker contraction speed. Type IIb fibers, on the other hand, are designed for short bursts of power and strength, showing high contraction speed but low endurance, making them more susceptible to fatigue. Type III is not a widely recognized classification in this context, reinforcing the idea that Type I fibers are the primary slow-twitch fibers known for their endurance capabilities.