This idea occurred to me about running in waves, meaning the training cycles through a season.
For example with a runner doing similar training every day, with very little variation in miles or intensity, the waves would all be the same. A race would not really stand out from the rest of the waves (days & sessions).
Examples of the steady waves are Zatopek & Peters, who ran more or less the same intensity and distance day after day.
Training with long intense sessions, and easy recovery days in between, creates big huge waves, with low depressions in between for recovery. An example of big waves is running 34km every 10-11 days at marathon pace, the other days easy/steady, with perhaps a session of 10x400 or 3x2000 in the middle. This is where all the fast times have been coming from recently, especially in the marathon.