Antonio & malmo - Easy there! I assure you that all of us would agree on virtually all things running-related. I am cut from the same mold as you, a product of the 1960s and 1970s old-school, "no shortcuts," "learn both from your predecessors and by trial and error" way of doing things. I have run on a daily basis with a number of the people malmo ran with at AW. I've seen all the trends, all the fads, all the "research" this sport has has to offer, tried them all, observed thousands of others try them all, rejected the crap and held onto the practical nuts and bolts. I consider anyone not cut from that same mold as a recreational dabbler and (if they start yapping about mitochondria) nothing more than an armchair quarterback.
In short, I believe we are on the same team here.
But because I mentioned the word "mitochondria," you made assumptions. I'll give you a mulligan on that one, but I would have thought people with your experience would be able to (as Jacob Bernoulli said about a mathematical solution sent to him anonymously by Issac Newton) "recognize the lion by his paw."
Regarding this "rebuttal" on exercise intensity boosting mitochondria, it's not necessary, but put one up if you've got one. I haven't seen anything that contradicts Dudley's 1982 findings. Quite the contrary; recent studies (within the last 2 years) still cite Dudley with the end purpose of getting fatasses to adopt high-intensity interval training (HIT) and stop giving the "no time to exercise" excuse. Then again, I don't spend too much time surfing around looking for such crap, because I don't want or need to "know as much about mitochondria" as "J.O." thinks I don't.
I will say this - increased size and number of mitochondria in all of your oxidative fibers (as you get from working at max VO2) is a positive adaptation from working out at those speeds.
The 20 x 400 at 5k pace was a random and hypothetical set of parameters used to create a distinction with another random, but faster, pace - 10 x 400 at 3k pace. I wasn't recommending those particular speeds to be used for those workouts. You can run 20 x 400 at that pace or you can run them at 3k pace or faster depending on where you are in a season or where the workout fits into your immediate plans. Duh.