The gentleman who wrote this (Swimming Fastest: Maglischo, Ernest: 9780736031806: Amazon.com: Books ) spoke at the USRowing clinic in 2005.
He said that rowing was 20 years behind swimming in its understanding of anaerobic threshold.
Many rowing programs, including the national teams, had been doing (and still do) what I think John is describing, since the mid 80s (determining anerobic threshold periodocally, and then doing work right at anaerobic threshold on a regular basis).
Maglischo said that he had formerly advocated the same thing. He said that he now thought that work at AT was not the best method to increase AT. He now advocates work at above the threshold and below the threshold (I think a lot like Charlie’s nothing-between-70%-and-95% method or whatever particular numbers Charlie uses).
I don’t know enough of the science to really argue one way or another. I do know that when we stopped doing AT work our results got better, although there’s always so much going on that it’s close to, or completely, impossible to ever tell what helps and what hurts.
By the way, if I wasn’t supposed to include a link, I apologize, and I can delete it (unless one of the gang in charge beats me to it).
The new approach is increasingly used in swimming and has been used in distance running for some time (Auita etc) and fits nicely into what I’ve been pushing for the last 30 years (some catch on quicker than others)