Rather than multiple calibration workouts, just do one good test. The KM test is the best, hands down. Once you get on-board, you’ll never want to do a 20 minute test again.
Very common. This problem was chronic on TR when the ramp test was state-of-the-art. Now that adaptive training exists this is still a problem it’s just that workouts get adjusted to make it bearable.
For your next threshold interval workout, start it with intensity lowered by 15%. Do the first interval. After that interval, if it felt ridiculously easy, increase intensity by 5%. Make the same decision at the end of the 2nd interval. It’s not going to take you long to find a work rate that allows you to complete the workout but still achieve a reasonable level of adaptation.
Next workout, start at that intensity plus a couple percent.
Next VO2max workout, increase the intensity by 5% right from the get go. See if you can still complete the workout.
This is a really interesting thread and very informative. I’ve been dabbling with TR and structured training, struggling to get some real consistency due to life in general getting in the way.
The one thing I’ve never quite got my head around is how hard intervals are supposed to be, or what “failing” an interval is? It seems pretty obvious for a VO2 interval as you can easily get to the point where HR is maxing out, your lungs are busting, and your legs are refusing to keep up the power.
However, when does a sweetspot or threshold interval become “too hard”? Are people getting to the end of a session say 4x10 intervals and they are literally unable to finish the last interval because of HR/lungs/legs?
To me, if I was doing SS 4x10 or something, and my HR was touching 90%, I’d assume the FTP was set too high or I was doing too long intervals for my fitness.
How hard should we be pushing ourselves? I mean, there’s training that’s hard and then there’s training that’s bloody miserable. I would assume that only V02 max and/or Anaerobic should be touching on miserable, surely threshold should be “hard”, and SS should be fairly hard?
I don’t see how a well placed SS workout can be “failed” because you are maxing out somewhere??
What am I missing?
4x10@90% you shouldn’t even feel 
you HR will be normalizing closer to end of interval. 10min at sst should be pushing pedals but there is nothing hard in it. Breathing stable, easy. There is no feeling in the legs, only need to push a little harder than z2. In my scale of pain RPE 6. You should feel that you have done some work but if you had to do twice as much - no problem.
4x10@threshold - first 5 min is easy, last 5 min your breathing is deeper but stable, fully controlled. Legs feels like working but no pain and discomfort. RPE is 7 maybe 8 for last 5 min of last interval if your TTE is low. You have never doubt about finishing interval but you feel that you have done some work.
This. For me only way to fail sst is going over 90 min without proper nutrition or pure mental fatigue. Anything below 80 min TiZ should be doable anytime.
Interesting, thanks.
So what is happening when people are failing SS/Threshold workouts?
I think people are missing some of the implications of this image
Describing vo2 as easy with a pl that low isn’t really surprising. 60 minute vo2 workouts with that pl are sets of five 30/30s at 115%.
They aren’t challenging enough to meaningfully assess vo2 related to ftp
All signs point to ftp being significantly too high, both as relates to threshold workouts and unknown related to vo2
Hi,
Usually those longer repeats are not failed because you are out of breath alone, but because of the lactate accumulation. If your FTP is way off, it can be a combination of out of breath and lactate accumulation, but usually it is just a slow failure caused by burning legs. And you get confused, since your lungs seems up for more.
FTP is a power you are able to hold for around one hour when fresh. Same as anaerobic threshold which have a similar definition. Anaerobic threshold is defined by lactate accumulation. When you increase workout intensity the lactate accumulates in your bloodstream exponentially. Anaerobic threshold is the breakpoint in your lactate accumulation. Beyond this point the lactate in your blood increases rapidly, that is why you are not able to hold efforts above threshold for very long. This breakpoint has been defined as 4mmol/L lactate, but there is (as everything else in traing theory) individual differences. For some it can be 3, others 4, or somewhere in between.
So, when riding at your true FTP you are slowly accumulating lactate (more than your body can clear), and at one point it becomes so unbearable that you can no longer handle it. You need to stop or decrease intensity.
If you (or some algorithm) overestimate your FTP, you will fail classic threshold workouts because of lactate accumulation. You are not working on that breakpoint, but above it, and lactate is accumulating too rapidly to complete the workout.
Another classic example is doing sweet spot intervals with an overestimated FTP. Those workouts are typically longer than threshold workouts. Both in total volume and in interval length. People often end up doing sweet spot intervals at their true FTP, and it just becomes to hard to keep up eventually.
Of course, you can also fail just because your muscles are not strong enough and is fatigueing. But that is more the case for very novice cyclists. I struggled with this when I first started cycling. I came from running and cross country skiing, and had a good engine, but my muscles could not keep up. Your muscles adapt pretty quickly, so this is just an outlier for very novice cyclists. As @jarsson mentions, fueling can also be a factor, but usually the problem is lactate accumulation due to overestimated FTP.
Simply not true for most people. Most people can hold their FTP for btwn 30 and 40 minutes.
Especially if their biggest threshold interval day is 3 × 10 or 3 × 12.
Only folks who deliberately do extensive FTP work tend to be able to hold that FTP out to or beyond an hour.
If you want to define it that way, then go ahead. If you define it as that then that is the exact reason you can’t do more than three sets of 10 minutes.
Their FTP is not their FTP. This is common.
Second thing - cooling. Long, sustainable efforts generate ton of heat. Your HR can go through the roof.
Nutrition - with 10min intervals it can be easily done without anything (but you shouldn’t). With longer things like 4x20 or 2x40@90% or with 4x15@FTP proper nutrition helps a lot when going closer to your TTE TiZ. Last interval is way easier when fueling properly.
I do not know whole mechanism of fatigue and why you faitigue over time, but from feeling perspective I only know feeling of being empty and without energy to push pedals but not pain in legs, burning in muscles and so on (when working under or close to FTP). Maybe when going over tte with threshold intervals las 5-10 feel like that - then I have to concentrate to hold the power, stare into bike computer to finish the work. But rest of the workout is usually pretty comfortable. That’s for me and it was the same since my first steady workout.
The physiology defines it, not me 
The human body has no idea how long 3,600 seconds is.
My last FTP test was an open-ended interval that finished at a shade over 50 minutes, fwiw
Hm, ok. I can go a bit harder for 30 minutes, and call it FTP since I gave it my all? I do not really understand, but I am listening. What physiological factor is the decider? The problem is that this quickly becomes a minefield. If FTP is 30 minutes maximum effort for one person, but 70 minutes for another, then you have to adjust all prescribed workouts individually. 2x20minutes at FTP would be hell for someone whos FTP is defined by a 30 minute max effort. Most likely not doable in the middle of a training block. That nullifies the point of FTP to begin with. A tool to gauge your efforts.
This has NEVER, at any point in any training block, been my experience for a single workout lol. 10
Minute sweet spot efforts were always like a 8/10. 10 minutes of FTP was about 14/10.
Last 5 minutes of a 20 minute interval was pretty comparable effort RPE wise to the last lap of a CX race.
Interesting. Yesterday I have done 3x8@110% FTP so I assume this is how people perceive threshold workouts given other comments 
How far does your RPE scale go? If breathing deep but stable, fully controlled and no pain, might be a RPE 8.
Typical 1-10. 5 is around LT1 for me, 5-6 would be tempo, 6-7 SST, 7-8 threshold, 9-10- last interval of threshold with burtsts and VO2 max work.
Good advice. Did that this morning and then decided to manually reduce my FTP by 5%
Hi Caro,
thanks a lot for this detailed post! I forgot that you guys can see all the workouts we do 
I switched to the polarised plan because I only want to do two interval sessions per week and the pol plan offers that. I also do two weights sessions which don’t show up on my TR profile. Perhaps I should switch to low volume, though in the winter months I’m more likely to do shorter rides but more often (indoors), but it’s worth trying.
Looking back over Jan/Feb, the mix was a bit different. Threshold sessions were often o/u and every week had one VO2 max, instead of two threshold sessions. That suited me pretty well.
You’ve given me things to think about. Thanks!
This correlates nicely with how the scale is defined, and I fully agree with this. If 10 minute SS efforts is 8/10 something is clearly wrong. Either your perception of the rating of perieved exertion 
, or (most likely) your FTP is set to high and you are doing threshold work, not SS…