Just got back from the gym. I applied some of the principles described in this thread. Had an excellent workout. Again, the 20 x 1 stuff is not my cup of tea, but this workout was pretty intense nonetheless. It was done on a recumbent stationary bike that has level settings from 1-20.
first 10 minutes at level 10, cadence mostly 90-100
next 15 minutes at level 11, cadence mostly 90-100
next 25 minutes level 12, cadence mostly 85-90
next 3 minutes level 13, cadence mostly 82-84
next 4 minutes level 12, cadence mostly 84-88
final 3 minutes lève 11, cadence mostly 89-92
The first 10 minutes I think of as more or less steady warm-up, and the next 15 is sold/steady aerobic work. For me, the third block is the key--it is like my "5k" block. It seems similar to 5k pace in terms of intensity, and I want it to span at least the length (in time) of a 5k (my 5k PR is 18:57). I was not thinking of going to level 13 today, but as I approached the 50:00 mark, thought: push it for just 2-3 minutes. This three minutes really worked me. I bounced back a little though in that final three minutes at level 11.
Some other thoughts...I also did a negative split in this workout, as I was at 9.76 miles at the 30:00 mark, and 19.70 miles at the 60:00. I actually went a little beyond 60:00 just to get to 20 miles. Sometimes it is little things like this that make a difference psychologically. The negative split felt good, too.
I recommend this workout, or something like it, for those of you who may be coming off of an injury or for those who simply want to get away from the pounding for a day...especially those who tend to not like conventional interval sessions. I basically "went as I felt," and so I did not feel the pressure of "Oh no, here comes another 6:00 pace interval." Further, for those who love progression runs (I surely do), you will enjoy this workout. It is basically a progression, as it "progresses" for 50 minutes.
I think this workout useful, and so I will start a new thread with it. Thanks for all the ideas in this thread.