“I’ve overtrained for whatever reason and need an endurance block or two” IMHO
I also pay a lot of attention to my heart rate, just as a measurement of my aerobic fitness.
A couple weeks ago doing intervals at high end of sweet spot, I was way up into a threshold zone, high 160s for me. In multiple workouts since in that zone, consistently low 150s through every minute of the work periods.
That’s just to say bad workouts happen, to everyone, and a single failed workout is absolutely nothing to worry about. You probably do have to build out your aerobic base, that’ll happen just by following your plan.
I had to take a few back spins in the last 5 minute stretch of lion rock today, and I actually found it reassuring. I knew I was a bit underfueled, so that being enough to keep me from finishing strong let me know I’m training right on the edge of my abilities.
yep
When I did Spruce Knob (2x30) earlier this week, 3x20 sounded sweet.
I don’t think this is the reason. If you are someone who skews fast twitch fibers, long, lower cadence tempo/sweet spot intervals are known to be effective at improving fatigue resistance (lowering VLaMax). For me, if I ride sweet spot at too high an intensity, my cardio gives up (or I put my cardio system under too much stress) before I get to the point of fatiguing my legs. Different approaches work for different riders.
I think there is something to this. I usually hold about 92 in cadence, even through the sweet spot long runs. Lately I’ve started to decide on a lower cadence for one of the stretches, just to give myself some rest but also to put some variables into my “mind game”. Mentally I can think: yeah, that’s like taking on this-or-that hill, a long one, when I tend to go down to 85 in cadence, so I do that. Just to put my legs to work more I might even drop down to 80, but I have a hard time holding such a low cadence. It drifts back up.
Nothing intelligent to add here. It is just that I am about to do Juneau -1 (SSB2MV). I had considered changing it to plain Juneau but decided against it. I want to compare my notes with last year, where I wrote “Boring, had to stop after an hour to look for some entertainment.”
I don’t pay much attention to HR during a workout. I will go back and look at it afterwards and compare with last year. It is rewarding to see that I have a 10% increase in NP with the same, or usually lower, HR. That’s not bad for a soon 67-year-old.
Fatigue is the key part - if they are at the end of a training week your HR will be higher. FWIW my max is 179bpm and SS is usually 145-160bpm. In a 25 mile tt I am usually 162-171bpm and in a 50mile tt which is a SS effort 145-155bpm. So anything peaking around Max - 20-25bpm is OK especially if fatigued in my opinion
Thank you all for your time and your responses. I had a hard night because I was dreaming about this workout 
I have analyzed every parameter of the workout and beside hr nothing was off the chart - pwr/HR, decoupling, cadence, nutrition etc and most important thing for me that in terms of legs the workout was not heavy at all. I am not over trained because I am following LV with no additional rides outside. I have a fan now so I will give a try custom 1h 2x20 galena on Monday with first two intervals - because the lack of cooling is only variable I have not covered and if legs were ok I suppose I could simply cooked inside my body. I think that working without a fan on SSBI and SSB2 was possible because a much lower power generated during the workouts hence less heat.
Get a fan!!!
He just got one (post right above yours.
Ah, I see that now, awesome. 
Posted early - and just finished Tray Mountain +3 - 4x20mins@90% FTP - HR 147-154bpm for the intervals - had to focus but with a max of 179bpm all under control - I think my FTP is set correctly based on the feel of today - although with Fang Mountain+2 yesterday only reached 164bpm - I would have expected higher…but big fan blowing in my face - can’t train inside without one!
Proper fans are a game changer. I think many people underestimate what massive flow difference there is from a standard circular vs blower style.
The more I read about it the more I understand my mistake Tommorow I will try big and powerfull circular industrial fan, but during the week I should receive the blower style fan. Currently the only fan I had was my cat and he was not good at it 
This is another important part of his debate about the how SS intervals “should” feel. If FTP is set too high, sweet spot intervals become more like threshold intervals, and RPE and HR will drift too high.
The ramp test over estimates my FTP. Even the 20 minute test I think overestimates my FTP, although not to the same extent. (Note: I’m interpreting FTP here as meaning the power that corresponds with MLSS - something I could hold for 40-70 minutes).
Using a heart rate cap for SS intervals acts as a check in case FTP is overestimated (“vanity FTPs” as Steve Neal has called them).
This is a different point than I was making above about how SS intervals “should” feel. But it’s true (for me) that lower cadence makes the interval feel easier. Below is a recent interval I did. You can see a distinct drop in HR for the 2nd half of the 2nd interval when I reduced my cadence.
Looks like training is working!
There’s always going to be a bit of debate on these longer workouts. Frankly, a 20min effort in SS should have the rider reach a very obvious steady state. If you HR is constantly increasing - which in the above screenshots, it is - it’s a good indication that your aerobic conditioning is lacking or your FTP is too set too high.
These are steady-state, sub FTP efforts that are wayyyy long enough to settle in. So, your physiology should settle. If it’s not settling, revisit your zones/retest etc.
Good point that - with mine today there was only a 7 bpm drift from first to last interval and aside from the first couple of mins as you settle in mine stayed pretty constant - interval 1/147bpm 2/150bpm 3/ 152bpm 4/154bpm - although cooling is vital as it is winter now and I find it more difficult to keep on top of this if I do long SS intervals in the summer.
It’s the former for me - need to improve aerobic base, and reduce power/HR decoupling in workouts like this.
Another reason to pay attention to HR when evaluating intervals like these.
Thanks … yes, slowly but surely. I am ok with slowly but persistent
I bought a fan, I have taken 2 first galena+1 intervals as a workout. I have eaten exactly the same meals today and the fuelled in the same manner on the bike. Today was a work day so I am more tired than on Saturday.
The difference was like a night and day:D the workout that was very hard has become the normal workout. It has felt more like 85÷ threshold than 95÷
My HR was 15 bpm lower on two intervals. I have messed up my fan position during the second interval so it went up. But in terms of RPE I have a feeling that now I know what sweet spot is and how it should feel - I was simply cooking inside before.
Thank you all for your help and your insights. The great secret was simply a fan and proper cooling