So fast simply means the breakdown of ATP is quick. So we break down ATP very quickly and that means the muscle contraction is high. Now, just like slow oxidative, fast oxidative also uses aerobic respiration and that means it also contains a high supply of oxygen. It also contains a lot of myoglobin. So these muscles also appear red but they also appear pink. So that means the amount of myoglobin is lower in fat oxidative than in slow oxidative.