So instead of 20 seconds work and 40 seconds recovery, what is your format?
Sorry, didn`t mean to be inscrutable
I do 2:1 work:recovery, so basically the exact opposite of yours; when I do 40 seconds of work, I follow with 20 seconds of recovery.
This morning was the StairMaster. After a progressively harder 5 minute warm up, I did 40 seconds work and 20 seconds rest, total of five times. That`s my "easy 5 minute cardio workout" for the StairMaster; on my "hard 8 minute day" I do 32 seconds work and 16 seconds rest done ten times. Since the Stair only goes so fast that`s my version of variety.
On the AirDyne, after that same warm up on the Stair, I get on the Air and do 2 minutes kinda easy just to get into the whole "I`m doing the AirDyne now" mindset and then do 20 seconds as hard as I possibly can followed by ten seconds of recovery. I repeat that as many times as I can while not letting my rpms drop below 80 during the work part and trying to hit at least 100rpms, even if it`s only for a few seconds. During the recovery I just keep it moving while trying to breathe. That "as many times as I can" is only *four or five* intervals, and I seldom do the fifth one, it`s hard enough to just stay on and do the 2 minute cool down (sometimes I simply end up on the floor and have to climb back on for the cool down after I`ve *really* recovered enough).
I added the StairMaster warm up to my AirDyne routine as gets my HR up there without wearing me out; doing my whole warmup on the Air wasn`t enough to do that unless I worked so hard that I was too played to really hit my work intervals properly. Since the Air and Stair affect me differently, this works better.
Those are REALLY short cardio workouts, huh?!? And I only do them every 3-5 days. I just focus on those work intervals being as hard as I can do. This works better for me than the longer sessions I used to do, which were also demanding but in a very different way so I`m really glad I switched even though it *is* infinitely less pleasant while I`m doing it.
I`ll be interested to hear whether the Niacin`s working for you. Speaking of Niacin, my wife used it for a while and it did spike her HDL numbers; she quit taking it, but her numbers stayed up there anyhow! No idea why, but I`m glad it worked for her.