Which muscle fibre type produces more lactate during high-intensity exercise?

Which muscle fibre type produces more lactate during high-intensity exercise?

• A. Slow twitch fibres
• B. Fast twitch fibres
• C. Intermediate fibres
• D. Slow oxidative fibres

Answer: (B)

During high-intensity effort, muscles rely on anaerobic glycolysis because oxygen delivery can’t meet demand. Fast-twitch fibres have a high capacity for glycolysis and relatively low reliance on oxidative metabolism, so they generate energy quickly by breaking down glucose to lactate when oxygen is scarce. This makes them the main source of lactate production under these conditions. Slow-twitch fibres are rich in mitochondria and favor aerobic metabolism, producing far less lactate, while intermediate fibres can use both pathways and produce lactate to a lesser extent than fast-twitch fibres.