Learning Objective
Compare the structural and functional differences between white (fast) and red (slow) muscle fibers, and explain how these differences determine muscle performance and endurance.
White Muscle (Fast, Power Muscle)
- Large, powerful muscles used for short-term, high-intensity activity (e.g., ocular muscles, sprinter leg muscles).
- Key characteristics:
- Large mass per motor unit
- High ATPase activity → fast contraction
- High capacity for anaerobic glycolysis
- Low myoglobin content → pale color
Activity
Red Muscle (Slow, Endurance Muscle)
- Smaller, less powerful muscles are used for long-term, sustained activity (e.g., postural muscles).
- Key characteristics:
- Small mass per motor unit
- Lower ATPase activity → slower contraction
- High capacity for aerobic metabolism (mitochondria-rich)
- High myoglobin content → red color
