Fatigue resistance of Type I fibres is high.

• A. Moderate
• B. Low
• C. High
• D. None

Answer: (C)

Understanding fatigue resistance in slow-twitch (Type I) fibres explains why this statement is true. These fibres are built for endurance. They have a high oxidative capacity thanks to many mitochondria, abundant myoglobin, and a dense capillary network, which together supply a steady flow of oxygen to the muscles. They rely mainly on aerobic metabolism to produce ATP, so energy is generated gradually with minimal accumulation of fatigue-causing byproducts like lactic acid. This setup allows Type I fibres to contract for long periods without tiring quickly, making them highly fatigue resistant and well-suited to endurance activities such as distance running or sustained posture. In contrast, fast-twitch fibres fatigue more quickly due to lower oxidative capacity, so their fatigue resistance is not high.