Finishing threshold efforts with a VO2 max burst

Hi all,

I’ve recently learned about the value of long threshold intervals e.g. 2x20 or 1x40 @ FTP.

Almost by definition, at the end of a threshold (read: Steady state) interval, I’m usually not cooked. I’m capabable of punching out 1-3 minutes at 110-120% VO2 max depending on how I paced the interval. Particularly on the last interval of a set where I don’t need to worry about saving myself for the next interval.

Is it beneficial to actually do so? I figure why not add some VO2 max adaptation to the back of a threshold workout if I can. But I’m not sure if adapting the two energy systems simultaneously makes physiological sense.

One obvious alternative is to use those same energy reserves to push 2-5% above threshold power for the entire duration of the interval, but I feel like the psychological toll of this is much higher, as it’s the difference between spending 30-40 minutes at MLSS and 1-3 minutes above it, and probably literally spending about 30-40 minutes at increasingly high lactate levels above MLSS. The ‘roll on’ of pain over a long period is pretty mentally crushing.

The other alternative is to just not do any VO2 max work in the FTP interval, thus saving yourself for the next days workout, but if real life forces more than adequate levels of recovery, that’s not always useful.


Intuitively, I wouldn’t think you would be gaining much by adding 1-3 minutes of VO2max work at the end of a threshold workout, but I could be wrong. You’re not spending much time at VO2max to push real adaptations. Though, I suppose at the end of a threshold interval maybe your O2 uptake is already quite high?

I think my first question though, is what is the purpose of your workout? Are you trying to increase threshold power? Or maybe increase fatigue resistance? If you want to increase the power, you should really be doing the entire interval at a slightly higher power. If you’re trying to improve fatigue resistance, the intervals should be longer. Either way, you should be pretty cooked by the end of a proper threshold interval, IMO. The idea of doing 1-3 minutes at 110-120% FTP at the end of a threshold interval would seem extremely daunting to me!

If you still have plenty of gas in the tank, maybe your FTP is not set high enough? I think I speak for most people when I say that towards the end of a 20min TH interval, the last thing one wants to see is a VO2 max kicker! :joy:



I don’t think that’s necessarily true. I mean, one oft-quoted FTP test is that it is around 93-95% of 20 minute power after cooking yourself with a short maximal effort and then a rest period. Conversely, you should be able to hold around 105-107% of FTP for 20 minutes. Thus, if you hold 100% for 20 minutes, there should be something left in the tank. The magnitude of that would depend on individual physiology, strengths and weaknesses (personally I have a strong ‘high energy reserve’ so I usually have a lot left).

All around fitness increase at the moment. If I’m doing threshold one week I might be doing VO2 max the same day a week later. Just wandering why not gain both at once if there is an opportunity.

I’m not sure that this is entirely true - after all, sweetspot work is used to increase FTP, no?

Having said that, I agree that doing it at slightly higher power may be beneficial and I would be interested in hearing what the benefit of doing it a couple % higher would be (in terms of adaptation impulse versus the lack of will that I would have to do that kind of interval). That was one of the alternative options I mentioned in my original post.

The aim of training is not to cook yourself.

The aim of training is to stimulate physiological adaptations.

The former can often impede the latter, especially in the long run.

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I do something similar in winter. Here I start around CP and increase power every 5 minutes 5 watts. At the end of the interval i reach normally around 92-92% HFmax.
From the RPE ist good sustainable, because the first half is pretty comfortable. But because is at and above CP, w’ is progressively consumed and both HR and VO2 tend towards is maxima.
So far so good. but there are caveats to this strategy. One can argue that the first 10 minutes are more or less useless and may not produce a great effect. Specially when we compare it . to the opposite, a fast start. Here you start with higher power to rise V02 fast to 90% and then slightly decrease power. But due to the slow competent of V02max the V02 is keeped high.
Rønnestad just talks about this:

I think one can make this 2x20 with increase of power, to gain some additional impact in V02max, but is not the silver bullet.

If a VO2 max session at the end was ideal, wouldn’t it have been added on by Chad?

As mentioned before, not every workout should leave you feeling emptied and push you to the limit… If I have anything left over I’m suspicious that the following workouts will require that.

Trust the plan :slight_smile:

I’m not sure that this is entirely true - after all, sweetspot work is used to increase FTP, no?

True, but you’re not talking about using sweet spot to push FTP, right? I assume you’re talking about true threshold work in the ~95%-105% FTP range. I believe that if you really want to grow your FTP via threshold intervals, those intervals need to be sufficiently challenging which would make doing a 1-3 minute VO2max burst at the end near impossible. You also need to continue to progress those intervals either through progressing the power you do the intervals at or the length of the intervals depending on your goals.

I also lean towards the philosophy that true threshold work should be used relatively sparingly since it can be so fatiguing. Which is why sweet spot can be so useful since you can do more time in zone with less residual fatigue.