Getting Whipped by Suprathreshold Intervals

I just can’t seem to get past these 4,5,6x8min suprathreshold workouts, and it’s starting to really demoralize my mindset. Anyone have similar experiences, or tips to get through it?

For context: started cycling in Feb 2018, relatively athletic; weight 63kg, height 173cm. Played around with Zwift from April-June, then found TR.

Went through Sweet Spot Base 1+2 mid-volume with no problems; it was challenging but doable, never felt like I wanted to quit a workout half-way.

Go into Sustained Power Build mid-volume about 5 weeks ago, and was able to handle all VO2max and over-under workouts. Completed Red Lake +8 (5x6min @ 108%). Go through the next round of VO2max and over-unders…BUT for the first time, ended up bailing on a workout—Raymond +7 (4x8min @108%). 3rd week completed the VO2max, and chose to skip the rest in preparation for a race weekend. Recover next week, and now in week 5, get to Stromlo +3 (5x8min @102%), and yet again, I bail a little over half-way.

Is it fitness-related? Mental weakness? :confused:

What’s causing you to bail?

Muscular fatigue and low cadence? Struggling to breathe? Or just too uncomfortable?

If the intensity of a workout is repeatedly causing you to fail (fueling, sleep, recovery etc all being equal) then I’d probably be inclined to reconsider if your FTP is still current/accurate?

There’s merit to dialing back intensity on an off day, perhaps longer above FTP is just a weakness. 4 x 8 min intervals at 108% isn’t to be scoffed at! The +7 might be a bit of a give away…

You also need to consider the workout/volume in the week that’s already preceded it too as some fatigue will be carried.

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Thanks for your reply @BennyC!
My breathing seems to be fine (not struggling or entering that heavy inhale/exhale you would see on longer VO2max intervals). I’m guessing it’s muscular fatigue?

Regarding the FTP, I considered whether it had been too high, but the fact that I can complete all other workout types in SPB at my current FTP setting is making me think it may be fine. Also retested at the start of week 5, and FTP increased 4 watts from week 1 of build.

I wonder if there’s a specific fitness I’m lacking where im able to complete 1-to-3 min VO2max intervals and over-unders, but not more than 2 or 3 8min suprathreshold intervals.

What did your cadence do over each interval? What did it average? What was it at the start, middle and end? If it’s steadily declining this would be a fairly good indicator of muscular fatigue (I think) or an area that just needs more focus/attention during the workout with some drills.

For me personally if I’m at or above FTP for any sustained period I can’t get away (without paying for it later) with ‘muscling’ it. So my cadence will usually exceed 92rpm and it will feel notably easier for me on the legs/muscularly as a result. Even though I’m still gassing.

Raymond+7 does have some fairly hard efforts in there, granted there is some pretty low power recovery but it’s relatively short at 4.5 minutes.

At 108% you are dipping in to VO2 Max territory and given the duration at 8 minutes there’s only so many matches in that box.


I also struggle with these efforts indoors and have come to conclusion it is a cooling related issue. I really struggle shift the heat once i’m riding above 300w. Very short and hard intervals are ok because the heat doesn’t build up, but i find it’s these medium length VO2max type intervals that cause me the worse problems. I’m fine for a few intervals but eventually it just feels like my body is shutting down. Outdoors I can complete the sessions easily.

Not sure if this is useful!


4x8 @ 108% is a hard workout, so it’s not surprising that you bailed.

Did you skip the rest week then fail Stromlo? Or did you do Stromlo after the rest week? It’s hard to tell from the post.

If you failed before the rest week, you are probably fatigued.

If you failed after the rest week, that is probably something different going on.

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I’d also add that it depends a lot on when you’re failing. If you pucker out on the second half of the last interval of a 4x8min, you’re probably doing it just about right - especially if you are using a smart trainer with erg mode.

My understanding that traditionally, when assigning intervals, you’d only fail the interval if you’d drop at least 5% below the intended intensity - a smart trainer literally doesn’t allow that sort of flexibility. You might just try to knock down the intensity a bit, even just a couple of percentage points helps and the training stress should be basically the same.

Thanks @BennyC
You’re absolutely right about pushing higher cadence. My legs wouldn’t survive those intervals at low 90, so I usually try to keep it above 100 to get the effect you describe. On Stromlo too, cadence never really fell, but it was more of a conscious decision to suddenly stop. Someone here mentioned heat, and after thinking about it more, this might have been an issue.

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Thanks @tcass
Actually that’s not something I had even considered (always quick to blame my engine, or lack thereof!), but it might make a lot of sense.

Wife doesn’t allow the AC to be on once the weather outside dips to 25 C (though she’s heavily pregnant so can’t argue with her :wink:). Temp inside the house is probably about 26-28 C, and I’ve only got one small fan at my side.

Ive noticed this especially with harder efforts in build on 1.5 hour workouts, where I’m sweating profusely and my stomach starts to feels strange (pukey). In Stromlo +3, it really did feel like my body was just shutting down, rather than muscle fatigue…but could be a little of both perhaps. I’ll try better cooling indoors and see if I can replicate outdoors as a test.

Thanks @stevemz

I completed the ‘Week 3’ rest week before Stromlo +3 (and admittedly Week 2 ended up feeling like a rest week, as the race that was scheduled for the weekend was cancelled…so only has a VO2max workout and a fairly hard outdoor ride).

Yes I don’t believe it’s general fatigue, but something else going on. Overheating issue perhaps.

I’m getting anxious reading this as Sustained Power Build MV is on my plan soon :wink:

speaking more generally, how about adjusting the intensity down a few % or taking a lesser version of the workout, e.g. -1 or -2 (relative to the current +x)?
this way you may still get quite similar adaptations and adjust to the type of the workouts.

@schmidt I was reading similar comments on how hard SPB is compared to SSB before I started…good to know my anxiety was well placed :sob:

But yea that’s what I’m thinking of doing to survive the last two suprathreshold workouts. maybe reduce intensity or even select the reduced versions.

@Peter Thanks Peter

You’re right about the smart trainer on ERG. Don’t really get a chance to see my watts slide (though a few RPM in cadence certainly would if fatigue started creeping in).

Out of the 2 workouts so far that I’ve ever bailed (both suprathresholds, both 5x8min intervals), the first i quit within the first minute of interval 3 (of 4), the second I quit about 5 minutes into interval 3 (of 5). Looks like an intensity drop might do the trick to get me through the last few weeks.

For me, these workouts are a real mental battle as much as a physical battle as they work through my threshold heart rate range which I call the “you should quit zone” since that’s when those thoughts creep in the most. I find if I can push through those thoughts and “embrace the suck” I can hang on a little longer. Of course as the intervals go along and the recoveries get shorter, hitting that quit zone comes on quicker each time. Either way, I feel your pain :grinning:.


@wyku I guess there’s only one true escape for us…embracing the pain until that last interval bring sweet release :stuck_out_tongue:

I’ll have to cool down a bit better, and learn to push through the mental break.

I had this workout this morning, so the timing of this thread was not ideal! I got through the workout and indeed it was tough. I think more of a mental challenge than a physical one. At 108% of FTP the workload is challenging, but doable. With the legs loaded up after the first couple of minutes of each interval, just trying to relax and focus on breathing really helped. I just tried to hold on until a couple of minutes to go and I could see the finish line.

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The cooling you need is evaporative cooling, from powerful fan(s). AC, wife notwithstanding, won’t do it.


@julianoliver glad to hear you got through it well! I definitely agree that it’s mental more than physical. I’ll try to create better conditions next time, and just push through. Fingers crossed I make it to the end.

@dbf mental fortitude and better fans. At least one of those is on sale.


:rofl: there you go!

I’m doing Sustained power build at the moment aswell and i’m also struggling with the same workouts. Cooling is definitely as issue, as your body temp just ramps up more and more as the interval goes on. I noticed it at the weekend doing Fish - 2. I baild out on the last set and when i stopped peddling i suddenly noticed i was sooo hot.

Probably just need another Fan.