BTW Stranger, I was able to browse a bit through that linked book, “Essentials of Strength Training and Conditioning - 3rd Edition”, and you may want to check out their chapter on endurance training, see for example pages 128 and 129. They take a view that is consistent with the traditional one: endurance training will allow for certain sorts of muscular adaptations that serve endurance activity well - no increase in strength, increased capillary and mitochondrial density and increased connective tissue strength. Selective hypertrophy of Type 1 fibers. Less body fat and no change in fat free mass. Maximal cardiac output increases with greater stroke volume. Now not all of the book is available on preview, but if there is a section that states that “LSD-type exercise is of minimal benefit over just normal daily activity, and real gains in endurance are made by stressing activities, in particular those that develop strength …” as you say it does, I would appreciate the direct quote. What is available on preview is quite not that.
I can find less skimming “Fit” on preview except that the bit under endurance emphaisizes, appropriately, variation, including LSD. See page 16 for a discussion about how a beginner should progress from low intensity then add volume and not add much interval taining until at least at the intermediate level then in order “to assist in driving and maximizing the aerobic adaptations made possible by longer duration and continuous activities …” Again, if this book states that there is minimal benefit of LSD elsewhere please provide the quote.
Also again, the question is NOT whether or not HIIT is great (presuming it is someone’s cup of tea), whether or not it cannot also lead to adaptations that serve endurance activity, or whether or not using some interval taining and even HIIT is useful as part of the mix even when someone is training for an endurance event. It is great and it can and it is. The issue is is your claim that LSD is practically worthless (“of minimal benefit”) and your claim that these textbooks state that (which would place them at odds with the medical bodies, something I doubt is the case).