So these are basically our postural skeletal muscles. Our skeletal muscles found in the back that basically give us our posture that allow us to actually stand and walk around without bending over or anything like that. And that's exactly why they essentially are slow to fatigue. Now let's move on to the type two A and type two B scale to muscle. These are known as fast twitching skeleton muscles because they actually contract quickly. Now just like type one, type two A also appear red under the microscope because they also have a high concentration of myoglobin.