I just saw something on another thread about this. If Elite atheletes are doing intervals like 1000m's in the mid 2 min range, and the human body responds to time not distance, wouldnt 6x 2:30 minutes hard be a better workout than 6x 1000m at the pace non-elites do them in??
Only if you race by time and not distance.
We do little bit of that very early in the season (like a fartlek - 3 minutes on / 2 min off - but we are on the track). It helps keep everyone on the same recovery and is a transition to being on the track.
But at no point in the racing part of the season would we do anything on the track that is not a timed distance interval (i.e. 800's or 1000's)...
It's nevertheless a legitimate approach.