Red and White Muscle Fibres

Not every muscle fibre is built the same way metabolically.

Red fibres (slow, oxidative fibres) are rich in the oxygen-storing pigment myoglobin (which gives them their colour) and in mitochondria, are well supplied with blood capillaries, and contract slowly but can sustain activity for long periods without tiring — they are suited to posture and endurance work. White fibres (fast, glycolytic fibres) contain much less myoglobin and fewer mitochondria, are generally thicker, and rely on anaerobic glycolysis for quick bursts of ATP; they contract rapidly and powerfully but fatigue much sooner …