Dunno. Searched the forum and it appears that Spruce -1 is 2x25-min at 85%. I’ve got (many) longer examples where my HR is freakishly flat (around 84% HRmax). Its both a thing of beauty and reminder I’m more of a diesel than a sports car.
Yet sometimes I’m “off” - one example I pulled up it was upper 80s plus day-after-Napa-wine-drinking plus high stress at work… and HR drifted up to 90% HRmax during a longer ~60-minute tempo interval. Understandable in that context.
The team leader for WKO is the coach behind JoinBaseCamp. I did it this year, and can 100% tell you his 16 week winter base group coaching program had no progression that looked like that. Much smaller progressions. From my point-of-view that slide is a concept (listen to the WKO webinar again), and I’m a huge supporter of WKO and JoinBaseCamp and Tim Cusick’s coaching philosophy (big picture, I have developed my own opinions).
That said, at the end of the 16 week program I went out and did a 1x64-min at 86% (temp: upper 70s) and it had my signature freakishly flat HR:
Ran out of time, was happy to finish but could have kept pushing for 90-min.
My current philosophy is to lay down a strong endurance foundation, and layer that with a lot of low/high cadence work, short power work, and some (barely if any progression) tempo/SS work although I personally find 1-min hard start / criss-cross / burst formats to be “better.” Under my coach we did a lot of what forum members might consider to be ridiculously short intervals, the strict tempo work was often just 2x15 bookends, or the surprise 1x30 or 1x60 tempo starts on long 3-5 hour rides. The JoinBaseCamp programming was also interesting, somewhat of a grab bag too, some longer stuff with sit/stand, some longer with bursts, and a few progression sequences slowly going from 2x20 to 2x25-min (don’t hold me to specifics). In short, under both systems there was a lack of strict linear progression, however under both I was fully capable of going out and slaying a 1x90-min around 85% (+/-) and continuing with training.
Just wanted to put that out there, as I’ve learned strict linear progression isn’t required to jump to doing longer 60+ minute tempo efforts.