Polarized is about majority of training below LT1 and some above LT2 with nothing between LT1 and LT2.
It is this ratio which seems to get people confused and how much you "need" the higher intensity. There are a couple of interesting real world type studies looking at training data on thousands of individuals both elite and amateur now showing that the more base miles you run at zone 1-2 HR the faster you are in the race irrespective of anything else,
Does that apply to short races that are high intensity almost all the time (eg CX)?
I'm assuming that polarised and Z1-2 training is basically for people with the time to do a lot of miles at zone 1-2? I don't see how it can give enough stimulus if you are restricted to a few hours a week.
So there are a few things I was mulling over about polarized training recently:
1. It's pushed a lot in rowing. The standard distance is 2,000m. A top level athlete is looking at under 6 minutes. Which happens to be specific to Z3 under the Seiler polarized training model, but it's not specific to most cycling events, which are longer duration.
2. Traditional base type training as exemplified in the TR plans is not polarized training, it's pyramidal. This approach has been seen in some studies to give better results for cyclists than polarized.
3. The sweet spot base approach is pretty much the inverse of the polarized. A lot of the work is done in the areas specifically avoided by polarized training.
4. Matt Fitzgerald has written about the time vs intensity trade-off and he argues that even at 4h a week, polarized wins.
I went to an interesting talk about rowing training recently where polarized was advocated (guy giving the talk was Tony Larkman). He recently won the British Virtual Indoor Rowing Championships in the 50-54 age group, with a 6.19 time. That's faster than anyone I know of in our club, best in my 4+ we were winning regattas in is 6:34, and he was under 30.
Having said those things, my best overall fitness results have come from following TR sweet-spot based plans in 2016. I got less fit, I think, during the times when I was doing the most rowing, because I had less structure, and less time available (due to the travelling involved in going to a rowing club - particularly the insistence from the coach on doing land training at the club). I also had a break in training due to injury and illness late 2017-early 2018. During the 2018 regattas season, I struggled to do much time on the bike because I was always so tired. We did win at 4 regional regattas so it was probably worth it.