When I’m targeting long 90-180 minute climbs, those are usually completed at high tempo = 85-90%. In that context I like to progress out to a longer 90-120 minute single interval. Ultimately it comes back to what you are targeting.
54 minutes TiZ divided by 175%?
Good old fashioned 1x120 @ 90% today. I’m a bit worn down from a long 12 week base period and some big weeks, but very encouraged to hit such a big workout while tired. Makes me think my aerobic game has levelled up.
And you increase TTE by extending intervals and going over TTE… You can increase your TTE@FTP by doing Z2 if you go long enough.
I have seen it… not again, I do not want to do it this year 
I just knocked this out. I wasn’t planning to, but the first of my 2x50 was a cruise at 93-94% so I decided to go for the whole shebang.
Hilarious (to me) to see it mentioned. (I know, trivial coincidence but still).
Thanks all for the comments and the follow on discussions. I am here to learn and take advice so these differing approaches and opinions on how to progress is great. I will try and address some of the queries etc in a logical way!
For the 2x30 at 90% average HR was around 84% of MaxHR - I have seen the figure in the comments on this thread to aim for being around 85% MaxHR so feel like I am in a good spot.
The reasons for targeting 90% FTP for the SS block is based again on this forum thread and my desire to push out to a 1x90 SS interval. 90% might be low but the primary purpose of this block is to push my curve to the right somewhat and provide confidence in riding continuously at a good % of my FTP.
Riding 90m at circa 4.5w/kg feels pretty enticing and aligns with a lot of the type of more competitive riding I do. I also want to improve my fatigue resistance.
This is correct. My FTP TTE based on my KM Baseline Test at the start of the SST block was around this. Pretty poor I know (but a baseline and a starting point to take forwards) and one of the reasons I want to build confidence at doing a SST progression at 90% in the first instance.
That is my current thinking. At this stage I want to cement and build by aerobic base. At the end of this SST block I will assess and see what I need to do next; this might be another SST block with less progression but higher %, a short VO2 block to raise the ceiling (my fractional utilisaton is pretty high at the moment), or working on extending TiZ at Threshold.
What does the group think about increasing frequency of SST workouts over longer durations sessions.
For example building 60 mins SST tues, wed, thurs on the bounce rather than extending to 90 mins (for example) on Tuesday and Thursday.
Comments welcome.
My completely unqualified comment is that I think it would train something slightly different, maybe more a form of fatigue resistance, without doing as much for you TTE.
Also think it might make it more likely to create a lot of fatigue without much additional benefit.
Also agree with Splash, I think you’d build some great fitness (and accumulate a decent amount of fatigue to recover from Friday etc), but you wouldn’t achieve the same adaptations as long SS Intervals/Sessions depending on where you are in terms of progression and how much is required to provide some overload.
Classical block training. You increase training density to introduce new stimulus. It can create great results but it’s hardly sustainable in a long term:
I would use it sparsly but it has it’s place and can yield great benefits - like with vo2 max work.
So more progression of the reps in the session rather than adding days. Ok. I’ll move to that.
2 x per week?
Depends what outcome you’re looking for and how stretching those 2 workouts are for you I guess.
Only 2 SST interval sessions would generally feel a little unfocused/easy for me, as I’m a diesel. However if they were both 120 min sessions then that’s another matter…
I’m more of an explosive rider wanting to improve ftp.
Do you suggest 3 workouts?
Hard to say, but generally speaking I’d expect that type of rider to find SST harder. I think you need to play it by ear - build up gradually.
just knocked out a 3x25 today and it was dead easy, HR didn’t even crack 145bpm. Certainly time for a proper test to see where the FTP now sits. The one nice thing about doing these long SST blocks is they mentally prepare you for doing a proper long (25-35min) test as a lot of that is mental and chunking a long interval into smaller bite size pieces.
Happy to report that I just completed the 1x60 @ 90% without a hitch.
As others pointed out it was definitely a mental thing I was facing in terms of doubting my ability - thanks for the vote of confidence everyone 
HR was stable throughout, averaging 83% of MaxHR across the interval. Legs started to feel a little heavy in the last few minutes but I think that was due to the anticipation of finishing and not remaining as relaxed as the previous 58 mins!
Another 1x60 @ 90% later this week and then on to 2x45 @ 90% next week…
Is anyone here doing their sweetspot blocks at lower cadences? I have been reading some compelling info on this and started doing it at the start of this seasons base sweetspot efforts.
The theory behind this is that, by riding at a higher intensity, and at a low cadence, a greater number of muscle fibres will be recruited as compared to riding at higher cadences, due to the high force demands placed on the muscles (remember force demands go up as cadence drops and/or as power increases). In particular, this type of workout will recruit muscle fibres that would not ordinarily be recruited in a Zone 2 aerobic development ride until the later stages of riding when muscle fibres begin to fatigue and pass over workload to other fibres (Altenberg et al., 2007; Vøllestad et al., 1984).
Pro: Low Cadence Training (Compiled Info) - #19 by bbarrera
Basically - if you want to do them, do them. But you do not get any additional aerobic or strenght benefits other than being accusotmed to the effort and have bigger “arsenal” of cadences to use during your riding.
I use tempo for low cadence work, usually 40-60rpm on flat terrain to get high enough torque.
Personally I’ve found low cadence work to always improve FTP. YMMV.