Secondly the author tackles the issue of the flash running on water and using shockwaves to fight enemies. Here he explains that when you encounter a liquid it must move out of the way and the denser the liquid the harder it is for this to be accomplished quickly. The air not very dense compared to water, so the speed at which an object is going for the air to form a pleasure wave is very high. Air molecules move around at the speed of sound (750mph or 1,100ft/sec), when you exceed this the air molecules are pushed in front of you and form a shock front. Thus if the flash is moving faster than the speed of sound he creates a preasure wave in front of him that could theoretically be used to hit a villain. This same principle allows the flash to run across water, when his foot hits the water at incredible speed the water can't move out of the way fast enough and creates a shock front that pushes against his foot. At such speeds the water would behave like a solid.
Next the author explores the inability for The Flash to communicate with others while running and vice versa. Since The Flash is moving as such high speeds, the Doppler effect would cause any sound waves that reached him to become compressed as he moved throws them. Additionally, since he is moving beyond the speed of sound he would be moving faster than any sound waves and thus could not hear anything spoke to him from behind or the sides while running. Referring back to sounds he would hear from the front, they would become heavily distorted since the waves become heavily compressed has he moves closer to the point of origin. All this adds up to say that the flash would have to rely on visual communication while running because sound would either be slower than he was or would be compressed and register in a very high pitch.
Finally, the Author briefly describes the ability of the flash to grab bullets out of the air. Since the flash is able to move at the same speed as the bullet it would be moving along with him and just like picking up and object in a moving vehicle it would be as simple as grabbing it out of the air.
The author ends by describing how the flash would have to endure the extreme forces of accelerating to such speeds and decelerating back down over and over again. Which, yes, would kill a non-superhuman.