Apparently you grossly misinterpreted my pithy "says who". What I meant by that was that it really isn't possible to say with absolutely certainty what is or is not optimal with respect to various interval workouts. Very few scientific studies have been done examining this sort of issue, for the very good reason that it's difficult to detect small differences between very similar training programs, especially given limitations on sample size, etc. OTOH, the empirical approach doesn't work very well either, simply because few coaches have the analytical tools, etc., required to really address the question. This is why my own workouts tend to be very "plain vanilla" in nature: I don't feel that any particular complexity can be justified, and I personally don't need much variety to maintain my interest/motivation. On the flip side, though, the fact that I recognize that few if any definitive answers are available here means that I generally don't question what others do, except when they claim some special magic to their approach (e.g., Warren G's championing of 30 s on/off intervals), or when their ideas just don't stand up to scrutiny (e.g., "strength endurance" training, use of relatively small differences in gearing when performing standing start training).
