Which type of skeletal muscle fiber is most important for an athlete running a 40 meter sprint?

• A. Slow oxidative fibers (Type I)
• B. Fast glycolytic fibers (Type IIb)
• C. Cardiac muscle fibers
• D. Fast oxidative-glycolytic fibers (Type IIa)

Answer: (B)

Verified step by step guidance

1. Understand the types of skeletal muscle fibers: Skeletal muscle fibers are categorized into three main types based on their contraction speed, energy source, and fatigue resistance: Slow oxidative fibers (Type I), Fast oxidative-glycolytic fibers (Type IIa), and Fast glycolytic fibers (Type IIb).
2. Analyze the activity: A 40-meter sprint is a short-duration, high-intensity activity that requires rapid bursts of energy. This type of activity relies on anaerobic metabolism and fast muscle contractions.
3. Match the muscle fiber type to the activity: Fast glycolytic fibers (Type IIb) are specialized for short, explosive movements. They contract quickly, generate high force, and rely on anaerobic glycolysis for energy, making them ideal for sprinting.
4. Compare other muscle fiber types: Slow oxidative fibers (Type I) are designed for endurance activities and rely on aerobic metabolism, making them unsuitable for a sprint. Fast oxidative-glycolytic fibers (Type IIa) are intermediate fibers that support both aerobic and anaerobic activities but are less specialized for explosive movements compared to Type IIb fibers.
5. Conclude the reasoning: Based on the characteristics of the muscle fiber types and the demands of a 40-meter sprint, Fast glycolytic fibers (Type IIb) are the most important for this activity.