It's a question of spreading the available energy, aerobic and anaerobic, evenly over four minutes. If you run one part too fast, you pay a price. If you run another part more slowly your overall time is slower.
“The evil that is in the world almost always comes of ignorance, and good intentions may do as much harm as malevolence if they lack understanding.”
“In the beginning of the human race there was no genetic load which would cause undesirable traits such as appear in offspring of marriages between relatives today.”