As an athlete at Wheaton well after Danny graduated, I only met him a couple times in person. I reached out to him via email when he was a professor at Centre College. In that email exchange, my last question for Danny was about the 6x400 he did on most “easy days”.
Me: What was the physiological purpose of the 6x400m on 1:30 sendoff "indicator workout"? It seems you ran that on most every day that didn't include a hard track session.
DH: That was called an indicator set. The purpose was to trace progress throughout the season, based on how well I could do that short set.