Under/overs and lactate clearance

Hello, I think under/overs are good for me and I “like” them. I call them “u/o’s” because I start with unders.

I can do them “under” ftp and “over” LT, however I’m not convinced these are the right levels; maybe too high.

Basically, my LT is about 5% higher than my ftp (in my interpretation I have a “low” ftp compared to my LT, Vo2Max and anaerobic levels, which is basically my whole training issue in a nutshell).

I can do these super-intense intervals, but they don’t seem to help my functionality as a racing competitor.

I’ve decided it is an issue of lactate clearance based on a long-term imbalance between “high and low.” Simply too much high and not enough low, for many many years on top of an ice-hockey background.

I understand and embrace the polarized model, and get the Z2 training on an 80/20 (4 to 1) program.

My question is at what level to do the"highs."

I have learned that the Seiler 8’s are best at 87-92% of Vo2Max, however my ftp is 84% of my Vo2Max, thus I am “above threshold” at that level, and dead center on my LT on that level.

Sounds silly, but those seemingly small percentages are very significant.

I can do the 8’s at this level but I’m not convinced they will “work” at that level. The issue here is sustainability and how to approach functional over-reach.

This is context for my u/o question, as my main 8’s approach is to be very aware of not going too high. Even a small jump too high messes up the process.


What are the optimal u/o levels?

I can do them around my LT, but this is super taxing.

If around ftp is better, what are the percentages? In other words do I go actually below ftp, like 10% below, and then actually above ftp, like 10%, which in reality puts me above LT, that is low Vo2Max, which is, again, doable and super intense.

Or, to do them “right” do I go 10% below, and then above, but only like 3% to avoid going above LT and therefore into Vo2Max?

The idea here, for me, is to use Z2 along with “hard” intervals, sustainably, to improve my lactate clearance, a real deficit for me, as I feel my high level is plenty high (though can improve), the actual limiting factor being lactate clearance (lack thereof, so-to-speak).

Thanks for any input,


PS, I guess it’s really a question of wondering if it’s better to do intervals, HIIT, below Vo2Max, or are all these intervals basically just variations on a Vo2Max workout.

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@Lmasursky I think you’ve posed some great questions but more detail is necessary while also simplification more than nitpicking the details (which sounds counterinutitive but from my coaching experience works).

For example the details;

  • what’s the ratio of the under to over duration
  • whats the total interval duration
  • how many reps and thus total time at intensity

And the simplification;

  • think about longer UO reps so you spend more time at intensity and at the end point when stimulus may be stronger
  • those longer reps maybe lower Rx Under:Over ratio output
  • shorter UO reps that are more intense by design thus higher U:O Rx power
  • and they should both be hard by design but more at the end point of the reps and especially completion of all the reps to gain an acute session adaptive signal

But the thing I see is the “highs” are hard and with your LT at such a high % of your max, sounds like you could use a cycle or two of “raising the ceiling” so you have more room to work your LT up again.

Not sure what other coaches responses and without metabolic or INSCYD testing to truly identify where your % of max and LT actually are. And the key to really know LT1 or Low intensity for the days outside of your intensity days so your peaks (intensity) are high and your valleys (recovery or LIT) are truly valleys.

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There is a related topic going in the Physiology Forum (Library & Forum Members) called Lactate Clearance.

Member @tshortt asks:

That topic may be helpful!


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Thanks so much for this response, digesting a bit.

What I do is 2 low, 1 high, x3; repeat x3. Meaning 27 minutes of work. 3-4 min. rest between sets.

If I do these essentially around my LT, which is what I’ve been doing, the result is 27 minutes of VO2Max, in that the average watts is above LT, and my heart rate is in the 95% range.

I can do these, just not convinced they work for racing training. Need to go lower.

Looking for an opinion on whether this sounds right, and that the u/o should be around ftp, avoiding touching LT.

My main thing is improving lactate clearance.

@Lmasursky From what you are describing here, I would say that your LT is measured too high, how did you test your LT?

An easy way to get a indication of your LT being tested too high is doing a 30 min test at LT.

If you can do this quit easy, still hard but doable with out going too deep and your HR not increasing more than 5 beats between 10 and 30 min of the test, then you are in an okay spot for LT.

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Hey, great question, awhile back I did a 20k TT here locally (Flapjack, Tucson area), well, 2 actually. The first one went really well for me, my number was right on in terms of where I thought it would be (a bit above my projected FTP). Once I did the second one, the whole effort averaged out to be my expected ftp essentially an hour of power.

My HR stabilized on both efforts, and especially on the first one I pushed hard for the last 3k-HR going up accordingly.

I took this to mean I was barely at or just below my LT on that effort, so I put my LT target a few watts above the number.

If I go much above that number, I’m in VO2max for sure, HR goes up fast and my time to shutdown goes down rapidly.

Just having written my question and read the responses, it’s obvious now that u/o’s have to be around ftp, and stay at/below LT on the “o’s.”

Again, I can do them harder, and it’s actually “fun” but this it doesn’t help with my racing as I continue to lag on lactate clearance.

Underlying this is a painful and boring history of doing sweetspot/LT training, maximal misery, minimal gains, hated it.

This is opposed to polarizing, where I have fun doing it, feel like I make gains; recognizing I could do more to improve lactate clearance.

Going forward I’ll stick with “fatmax” Z2 rides, with high sessions, weekly, of Seiler 8’s, and u/o’s around ftp, being careful the “o’s” stay =< LT.

Thanks again,