Threshold intervals too hard

I just read this post (and congratulations to OP!) and it really brought home to me how much I struggle with longer 100% threshold intervals. I’ve been doing the MV polarised base plan which has lots of 7-9’ intervals at 95-100%. I frequently have to dial down the percentage to get through them. The thought of riding at 100% for 50’ is inconceivable to me. Should I manually reduce my FTP?

Bit of background to my training: My AI FTP is 215. In July/August I did an ultra bikebacking event that effectively had me riding at Z1/Z2 every day for three weeks, so I’m not lacking in base fitness. Took me a bit of time to recover from that but now I’m back to regular training, but I’ve just not really felt that my AI FTP “fits”. Threshold sessions are too hard, short VO2 max too easy. I’m not training for anything particular right now, so it doesn’t matter, but it’s a bit demoralising to be struggling with these workouts.


Its a commonly raised question but if you feel you need to dial your FTP back, do it. I did pre AI FTP D and had my best season on the TT bike. (My well paced 20min tests were giving me circa 25w more IIRC, but I opted for my lowest 20mins test value as being more sustainable day to day). For me AI FTP after initially being too high (in beta and pre the 10 TR indoor rides requirement) but now its come into line with what I lowered it to a few years back.


Might be muscular endurance: flying through short VO2max thanks to anaerobic contribution but struggling with longer Z4 intervals :thinking:

I used to be same way, even after 3years of structured training with TR. What eventually helped, was 2 months of high volume / low intensity of Z2. After that quantity somehow turned into quality, TTE at FTP went from typical ~35-45min → 70min. Also, now I prefer 5min VO2max intervals.

Or if you don’t want ride only Z2, you can try TBHV 1-3 plan.


Maybe you will find something helpful here:

If you struggle at intervals 7-9 min long@100% FTP I would personally start with lowering FTP. 10 min intervals should be around 7 RPE, maybe 8 in couple of last intervals done at 100%.


I’m coming up to 11 months of TR and you’re not alone, even 20 minutes at Threshold was inconceivable to me at the beginning and I found short VO2 intervals far easier.

It took a long time to get comfortable with longer periods at threshold, but over time it did get easier to get through them, both in terms of fitness, but the old cliché of getting comfortable with being uncomfortable. 6-8 min intervals would be a struggle and I’d be marking some Very Hard / All out at the beginning, or even knocking down 5-10% on the bad days. Don’t be afraid to back it off a little.

The turning point was my first trip up Sa Calobra in May. It’s far easier to do it outside and up a hill, especially with others around you, but once you know you can do it for 50+ minutes, that confidence drastically helps indoor workouts IME.


What about them feels hard, what is giving up?

It’s the burning in my legs, i.e. lactate build up, that limits me, I believe. I don’t give up as such, just dial down the watt target or take breaks, but it is demoralising.

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Well, I’ve actually done massive volumes of Z1/2 over the summer, but sadly not seen any benefits from that.

Thanks! Yes, maybe I’ll just lower my FTP a bit, just to see how it goes. For VO2 max I can always dial it up, if necessary. Just a bit sad to see that the clever AI is maybe not so clever after all.


Haven’t done yet any myself so I wonder how does this work?
It sounds like your VO2Max PL is at 10 and still not a challenge for you while your threshold PL stucks at 1.0 as you mark every workout as failed?
Can that really be?

Sorry, I don’t quite know what you mean by this?

If threshold is too hard and VO2 is too easy then it sounds like your FTP is sort of in the right place and Training Levels should update to give you workouts in both those zones that are about right.

How long have you been on the TR plan? What level are the threshold workouts you’re struggling with? How are you filling in the questionnaire when you’ve had to dial them back?

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I’ve struggled with the same. I think that Ramp Tests and AI can tend to overestimate for those of us who struggle in long Z4/5 efforts, but who can also stomp out high wattage Z6/7 when needed. For me, lowering FTP maybe 5% definitely helps. Turning off Erg can be helpful too as you don’t have to hold exactly the target number. Also, I can hit higher FTP numbers when doing long intervals outside than I can inside. Knowing all those things allowed me to admit to myself that some days it’s ok to lower/raise things a few percent and completely changed my training experience. “It’s ok to go easy when you’re not feeling it” and “it’s ok to go hard when you feel stronger than expected” were huge game changers for me. I know that seems obvious to some, but for me, it was not.


PL = progression level
If you check your TR carreer page, what PLs do you see for threshold and VO2max?

Thanks. Been on this plan for about 6 weeks I guess. Struggling with all the sessions that are 7-9’ @ 100%. I can manage 95%, just about, and I always put “ver hard” in the questionaire or “intensity” as the reason why I had to dial it down. I’ve not really seen many AI adaptations that really got me in the right zone. At this point the AI feels aggressively hostile to me tbh.



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When 9 minute efforts, or 20 minutes at threshold, is too hard or “inconceivable” it is because it’s not threshold at all. It is as easy as that. The sooner someone is willing to accept that, the better. I’ve lost count of the number of times I’ve read or heard about people driving themselves to the ground with “sweet spot” training that is actually threshold efforts, or “threshold” efforts that are actually suprathreshold.

Unless you have a bad day, or have a lot of accumulated fatigue in your legs, 4x10min, 3x15min, 2x20min or anything similar at true threshold should not need to be dialed down in intensity, or lead to failure. With regards to 6-8 minutes efforts; 4 reps of 8minutes at around 105% should be doable for most people, and is a great workout. A very well trained individual can up that to 6 reps. If 8 minutes at “threshold” is perceived as very hard, or all out, then your threshold power is set too high and it is in fact suprathreshold or perhaps even closing in on low VO2max… It is brutal, I know, but you are much better of being honest with yourself with regards to threshold.


Well I want to be honest with myself, but it seems the AI is lying to me :joy:. Maybe I should just suck it up and do a ramp test for a change.

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Indeed. So how this goes should be: You mark your VO2Max workouts as “easy”, as thats how you said they feel, and TR dials them up very quickly, until they stop being easy.
Similar for threshold, if you fail them (and mark them accordingly!), the PL should be dialed down so you can sustain them and improve from there.
All without the need to worry about your exact FTP value.

Thats at least I understand how TRs adaptive training is designed.

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First, I agree with you that this rider should probably just lower the FTP a few % for consistent workouts.

this riders PL for threshold is 3.8 and sweet spot 2.6, and I understand that they did a lot of Z2 over the summer. They may just not be accustomed to long harder intervals at this moment.

This whole “you’re doing something wrong if you can’t do 2x20 at threshold” is said so often. it’s a weird argument, because it only depends on the relative nomenclature.

We train with absolute numbers, however. For example, you can hold 2x20 at 220W today. Put your threshold high (eg 250W) and call it tempo/sweet spot or put your threshold lower (eg 225W) and call it “I can easily do 2x20 threshold”. It’s still the same time at the same W.

Obviously, doing 2x20 at 250W would be an unpleasant workout in that case.