And to a large degree they were right.
Endurance takes months and yes, years, to build.
And improvements in lactate threshold and VO 2 max occur on scales of weeks to months. While VO 2 max is a measure of the total volume of oxygen an athlete can take in while training or racing, running or racewalking economy refers to how efficiently the athlete uses that oxygen. Athletes who use less oxygen at a particular pace are more efficient than those that use a lot of oxygen. And since oxygen is a scarce resource, the more economical racer will get to the finish line faster. Economy workouts are aimed at improving high-speed technique and reducing the body's output of lactic acid at racing speeds.