RED MUSCLE FIBERS(Tonic) WHITE MUSCLE FIBERS(Twitch) 1. These are thin and smaller in size. 1. These are thick and larger in size. 2. They are red in colour as they contain a large amount of myoglobin. 2. They are white in colour as they contain a small amount of myoglobin. 3. They contain numerous mitochondria. 3. They contain less number of mitochondria. 4. They carry out slow and sustained contractions for a long period. 4. They carry out fast work for a short duration. 5. Sarcoplasmic reticulum is moderately developed. 5. Sarcoplasmic reticulum is well developed. 6. The fibres are supplied with abundant blood capillaries. 6. They are moderately vascularised. 7. Lactic acid does not accumulate. 7. Lactic acid accumulates. 8. They perform aerobic respiration. 8. During strenuous exercise, it switches over to anaerobic respiration.