Why would not a LIT focused approach work at lower hours?
Let me quote a couple studies. In the published case studies of the most decorated Norwegian XC skiing champs (espes. Marit Björgen: https://www.frontiersin.org/articles/10 ... 01069/full
& Bente Skari in Seiler's presentations: https://www.researchgate.net/publicatio ... 5/download
) there are a couple interesting things to be found. Namely, there is an over-the-career tendency where, because of a change in the training philosophy during the 1990s in Skari's case and because of stagnation in Björgen's case the athlete a) decreases MIT and HIT relatively but sometimes also absolutely and b) increases LIT and lifting. As a result, VO2max increases thanks to more LIT, as do fractional utilization measured in power at the second threshold, probably thanks to the concurrent lifting and endurance. Overall the distribution of endurance training was roughly 90+% LIT, and 3-5% MIT & 5-7% HIT, respectively.
Mind you, Xc skiing competitions are roughly 3min sprint races and endurance races of 20-120min, so high intensity. The time trial endurance races are constant max efforts, though paced, but still full gas. Mass starts are like very rough intermittent sessions, a bit like the final hour in the classic bike races, often decided in bouts of 20-30sec where very high outputs are required. Yet the top athletes clock 800hrs of LIT per year, year after year. Clearly it is not just junk. Similar pattern is observed in Norwegian champion skiers in general (see: https://journals.plos.org/plosone/artic ... ne.0101796
Interesting reads these, BTW. Not a lot of fancy stuff there. Just loads of disciplined work and, yes, winning.
In a study by Munoz, 4hrs / wk polarised got amateur distance runners to handsomely sub 40min 10km, some substantially under (say 37min30sec for those who performed their LIT at the lowest intensity). Not world beaters, but not bad either.
I am not saying that this automatically translates to the ability to climb well at threshold, as was mentioned above. But physiologically or let's say bioenergetically I see no reason why the foundations to climb well could not be attained by a LIT-led focus.
And yes, FTP does not bode too well as a surrogate of MLSS / the upper threshold when assessed in studies, very much agreed. But I must say that the power duration curve or critical power *might* become a future contestant of MLSS, as it is being pinned to physiological phenomena as we speak.