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 injunction that we should love our neighbors as ourselves means to us equally that we should love ourselves as we love our neighbors.”
“When you've played this game for ten years and gone to bat seven-thousand times and gotten two-thousand hits do you know what that really means? It means you've gone zero for five-thousand.”