White Skeletal Muscle (Fast twitch fibre) Their fibres are much thicker and of light colour due to the absense of myoglobin. The number of mitochondria is low in white fibres. They have little or no store of oxygen. They are meant for fast and strenous physical activity over a short duration as they get tired soon. They carryout anaerobic contraction with accumulating lactic acid, $e.g.,$ muscles of eye ball, flight muscle of fast flying birds such as sparrows