MWI, what's the science behind waiting for the HR to return to the same point each interval (which will require longer recovery as you move through the intervals) verse doing intervals on a set time frame eg. every 2 minutes? (making the later intervals progressively harder due to the higher HR). I assumed that the effort to maintain output under increased fatigue would cause the adaptations/progress.
Prior to training with have worked out the HR in which the aerobic systems (ATP/pCR / glycolytic) are dominate, HR is the easiest real time measurement of this, so we do an interval moving right into the anaerobic training zone, then we monitor the rest period to ensure they have returned to the aerobic zone, so recovery is sufficient for the next interval.
It's more hassle, but it is also a much better quality of training.
If your going for a glycolytic stimulus, the rest periods are short, we only let HR drop out of the zone briefly before starting the next interval, or if going for maximal watts / power we have a longer rest, with a shorter interval to minimise fatigue, so each interval is maximised from an output point of view. Fatigue will certainly occur and after a given number of intervals it'll be significant, but that fatigue metabolically is a good stimulus for adaption, HIIT without significant fatigue is a waste of time.
Just thinking out loud - option 1 means the full number of intervals can be done, option 2 means someone working harder at the start can't reach their desired output by the end and/or is sick
Full sets of intervals are awfully hard to do
Just a hint MWI, 20seconds, 1 minute, 2 minute what? I like the idea of the target - I'd set recovery at my threshold heart rate (174, 189 is max)
First sentence is spot on, it kind of depends what you are specifically training for as to the approach you take, both work, one will be better for a specific individuals goals.
174 is pretty high is max is 189, would suggest your pretty fit? during an interval do you go to near max HR?
Inregards to timing, unfit might make is 60% predicted HR max before starting the next interval, for a well trained person, it will be 70+% of predicted HR max, they'll recover faster at a higher HR.
We can measure all this stuff in the lab during a vo2max test or just playing around on the metcart - or you can use a calculator off the google and get a prediction, which for most people is probably pretty good.
Another thing to consider, at least in track and feild intervals are often based off a given distance, as it's sport specific, can also do this on the bike to mimic sprints, short hard climbs etc.