Re reading Running with Buffs today and thinking about Lydiard's quote: (paraphrased) "there are lots of runners in the world who can run 46 seconds for 400 meters, but only a few who can run 1:44 for 800 meters, or two laps of 52 seconds. Therefore it is far more essential to train endurance."
What if the runner doesn't have the 47-48 speed needed at the minimum to go 1:44? Isn't it necessary to train speed? This goes for 1,500-5,000 as well.