If there’s one thing that exercise researchers love to study, it’s interval workouts. They pump these studies out at an extraordinarily fast rate, one that’s impossible to keep up with. When we’re trying to take it all in, we often rely on the researcher’s conclusions and put aside our critical thinking.
This is important, because some research is using time at greater than 90% VO2max as a gold-standard for the effectiveness of a workout, without doing a longer-term interventional study. But should it be? VO2max intensity workouts are certainly important to a well-rounded training plan, but are we ready to disregard workouts that do not score well in this metric?
Host Rob Pickels sees merit in this research, but Trevor Connor expresses his skepticism of using time at VO2max as an effective way to compare intervals. He also expresses his concern that this research could filter down to athletes in a way that will mislead them.
Joining our hosts is Dr Bent Ronnestad, a premier researcher who is uniquely qualified to weigh in on this topic, largely because some of it is his own.
So, get ready to go to max, and let’s make you fast!
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LAURSEN, P. B., SHING, C. M., PEAKE, J. M., COOMBES, J. S., & JENKINS, D. G. (2002). Interval Training program optimization in highly trained endurance cyclists. Medicine & Science in Sports & Exercise, 34(11), 1801–1807. Retrieved from https://doi.org/10.1097/00005768-200211000-00017
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Rønnestad, B. R., Hansen, J., Vegge, G., Tønnessen, E., & Slettaløkken, G. (2015). Short intervals induce superior training adaptations compared with long intervals in cyclists – An effort‐matched approach. Scandinavian Journal of Medicine & Science in Sports, 25(2), 143–151. Retrieved from https://doi.org/10.1111/sms.12165
Rønnestad, Bent R, Bakken, T. A., Thyli, V., Hansen, J., Ellefsen, S., & Hammarstrøm, D. (2022). Increasing Oxygen Uptake in Cross-Country Skiers by Speed Variation in Work Intervals. International Journal of Sports Physiology and Performance, 17(3), 384–390. Retrieved from https://doi.org/10.1123/ijspp.2021-0226
Rønnestad, Bent R., Moen, M., Gunnerød, S., & Øfsteng, S. (2018). Adding vibration to high‐intensity intervals increase time at high oxygen uptake in well‐trained cyclists. Scandinavian Journal of Medicine & Science in Sports, 28(12), 2473–2480. Retrieved from https://doi.org/10.1111/sms.13277
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Rob Pickels 00:04
Hello and welcome to Fast Talk, your source for the science of endurance performance. I’m your host Rob Pickels here with Coach Connor. If there’s one thing that exercise researchers love to study, it’s interval workouts. They pump them out at an extraordinarily fast rate, one that’s impossible to keep up with. When we’re trying to take it all in, we often rely on the researchers conclusions and put aside our critical thinking. This is important because some research is using time at greater than 90% VO2 max as a gold standard for the effectiveness of a workout without doing longer term interventional studies, but should it be? VO2 max intensity workouts are certainly important to a well rounded training plan, but are we ready to disregard workouts that do not score well in this metric? I see merit in this research but Coach Connor expresses his skepticism of using time at VO2 max as an effective way to compare intervals. He also expresses his concern that this research could filter down to athletes in a way that will mislead them.
Rob Pickels 01:06
Joining us today is Dr. Bent Ronnestad, a premier researcher who is uniquely qualified to weigh in on this because some of the research is his own. So get ready to go to max and let’s make you fast.
Trevor Connor 01:19
Hi listeners, we just launched our premiere episode of fast talk FEM. In case you missed it tune in to hear Julie Young and Dede Barry chat with dietitian and author Jennifer Sygo about many concerns of female endurance athletes including the impact of the menstrual cycle, menopause and how sports nutrition plays into this. Have a listen and check it out at fasttalklabs.com.
Introduction to Today’s Episode
Trevor Connor 01:44
Well, welcome listeners. Today, Rob and I are doing something a little bit different. It’s just him and I sitting in the studio right now and I’d like to say we’re going to have a debate. We certainly have some differences of opinion on this, though I think we’re also going to agree a lot, but today we are going to take on, I think an important subject of something that’s happening in the research right now. We are reading more and more studies that are looking at or comparing intervals and comparing them in terms of how much time you spend at 90% or greater of your VO2 Max. The assumption here being that the more time you spend at 90% or higher VO2 Max, the better the intervals and this is an important discussion because we’re seeing now studies that are coming out that instead of saying let’s have one group do this set of intervals, we’ll have another group do the second set of intervals, we’ll have them do it for five or 10 or whatever weeks and then see which produces greater gains. Now they’re doing studies where they’re just having the the subjects do each of these different types of intervals once and then going, which produces greater time at 90% or higher VO2 Max and then saying the ones that produce the greater time or the better intervals and the really important question here is can you make that assumption? Can you say that?
Rob Pickels 03:09
Yeah, Trevor, I love the conversation that we’re about to have because this happened organically between us. Last week, we are going to record and listeners, you’re going to be hearing this episode coming up in the future, about how different intervals or different interventions can increase time at VO2 Max and Trevor, before we even hit the record button on that episode, you and I were already engaged in the conversation that we’re about to have today and we realized real fast that we need to have this conversation on air before we have the second conversation. So I love the organic nature that this is coming up. In my opinion, it really lends credibility that this is a conversation that we need to have.
Trevor Connor 03:52
Well, we’ve mentioned some of these studies in the past and talked about this time at 90% or higher VO2 Max and that’s a mouthful. So from this point forward, I’m just gonna say time at VO2 Max, that’s what they’re getting at. We’ve brought up these studies in the past and kept saying this is based on an assumption, we need to address this sometime. So I think this is the episode where we address it and again, this is really important to all you listeners, particularly coaches out there because quite often coaches or trainers will look at the research see a title, it says X intervals produce superior gains to these other intervals and a lot of these studies are now based on this assumption and so that’s really important to address because can you say just because it’s more time at VO2 Max it’s greater gains.
Rob Pickels 04:38
Yeah, Trevor and as you said earlier, we’re going to have a debate. At the end of the day, I think that you and I are both we’re moderately similar in our agreements, maybe just from slightly different viewpoints, but this is sort of science. This is the method that all coaching athletes have to go through because there are so many concepts. There are so many strategies out there. There are so many things that are the best possible way to go about something that they can’t all be right and what I see today is Trevor is going to put out his, I’m going to put out mine, you know what the listener, take these and integrate this information for yourself. Use this to encourage you to do more research of your own, formulate your own opinions and take in all of that knowledge that you can and ultimately come out of this conversation stronger.
Trevor Connor 05:26
This is certainly gonna be a nuanced debate, we might pause at some point and have a quick mud wrestle over it, but otherwise, I have my position. Rob has his position. They are different, but you’re going to see a lot of commonalities and neither of us is going to sit here and say this is an absolute. I think there’s good arguments on both sides.
Rob Pickels 05:46
I’m just going to argue on semantics until you give up.
Trevor Connor 05:49
There we go, okay.
Rob Pickels 05:50
Should we do it?
Trevor Connor 05:51
Let’s both just do the one minute summary of what our position is. Rob, do you want to give yours first?
Rob Pickels 05:56
No, man I’m taking I’m taking second position on this.
Trevor Connor 05:59
I haven’t seen yours. I gave you my notes. You got an advantage here?
Rob Pickels 06:03
Trevor’s Thoughts on the Correct Way to Look at VO2 Max for Interval Training
Trevor Connor 06:07
All right. So here’s my position, I am not going to say that doing intervals at VO2 Max power VO2 Max pace, where if we had you on a ventilator on a metabolic cart, we could see that you’re pretty close to your VO2 Max, I’m not going to say that those intervals aren’t valuable. As a matter of fact, they are a key part of my toolbox with my athletes. The argument that I’m going to make is that I think there are certain times of the year to use them. I don’t think it’s all year round and I don’t think that is the definitive metric of the effectiveness of intervals. I think that shows one particular effective way of training, certain energy systems, not at all energy systems, but I think other intervals can be effective and I just haven’t seen the evidence for us to make this jump to say, time at VO2 Max is now the gold standard for intervals and you don’t need to do studies showing the potential gains of intervals. You don’t need to do those 5, 10 week studies to see the effects on athletes. You can just look at time at VO2 Max and say this is a better interval because it produces more time at VO2 Max. That’s my position.
Rob’s Thoughts on the Correct Way to Look at VO2 Max for Interval Training
Rob Pickels 07:18
Yeah, Trevor, in some regard, it’s a little bit hard to argue with that. You kind of have a pretty moderated well thought out stance there, but for me it’s important to recognize VO2 Max as a determinant of performance, the physiological measure VO2 Max, we need to be separating that in our mind, in my opinion from a quote unquote VO2 Max interval which is trying to describe a range of intensities for the workout that you’re doing. So for me, I’m constantly and we’ll continue to talk about those things as to individual items, but at the end of the day when it comes to appropriate training, I think that it’s important that you understand the unique needs of the event that the athlete is doing and the unique needs of the athlete, the unique capabilities of the athlete and that different intervals different workout schemes are going to address those unique needs in different manners, but with that said, there is significant research that shows training at intensities that are 90% of VO2 Max or higher show laboratory improvements in measures like power at four millimoles. So a relatively middle of the road workload as well as VO2 Max and power at VO2 Max and these training studies show improvements in time to exhaustion and time trial performance. So without question training at these very high intensities shows large gains in a relatively short amount of time of training. In my opinion, this is some of the most efficient way that people can be trading.
The Paleo Diet Team 08:55
Before we continue our debate, this is a good place to hear from Dr. Bent Ronnestad, who talked with us about both energy systems and the appropriateness of using the term VO2 Max for intervals.
Dr. Bent Ronnestad’s Thoughts on the Correct Way to Look at VO2 Max for Interval Training
Trevor Connor 09:06
I’m a big energy systems guy. I believe that when you’re doing interval work you need to know what energy systems you’re targeting and really design the interval work around that, so one of the questions that Rob and I had that we discussed a little bit on the episode was when you’re doing work at this severe and intensity this close to VO2 Max, are you really hitting all energy systems because you’re gonna get some anaerobic work, you’re obviously going to be maximizing a lot of the stimulus you’re gonna get on the various aerobic pathways. Do you feel that these sort of intervals can really hit all energy systems or is this pretty specific?
Bent Ronnestad 09:42
I don’t think the interval to go to if you really want anaerobic focus, but of course you are involving for sure that system, but in my point of view, not to a maximum so if I would really have a focus on that anaerobic, I will probably go for something else.
The Paleo Diet Team 09:58
What do you feel you really training and when you’re doing these intervals that are maximizing time at VO2 Max?
Bent Ronnestad 10:03
yeah. So when you’re looking at the signaling pathways, what is being activated at which intensities, but by using these intervals, I think you’ll get a big wide shot at that, because you are kind of emptying the glycogen stores. You are having a very high blood flow and the PGC, one alpha is probably very well stimulated and in a way, you can say that you get a lot of your efforts, a lot of different stimulus and people usually call these intervals like VO2 Max intervals and that’s maybe not a very good name or it could be a very good name, it depends, but but you get the impression that you only affect VO2 Max and probably that’s not correct, you can get a very good training effect on your threshold power.
Trevor Connor 10:48
So I agree with that, I think you need that time at intensity. So an important distinction that’s made in this research is it isn’t just achieving an intensity close to VO2 Max, it’s actually just looking at, which produces more time. So often these studies will look at multiple intervals, that all get the athlete to VO2 Max and what they’re differentiating is which interval produces more time at VO2 Max and I think that’s an important distinction as well.
Rob Pickels 11:18
Yeah, I think that is the logical conclusion, though. Where when you’re assessing the signal of any interval prescription, you’re looking at ultimately intensity and duration. If we really narrow things down, there are other factors we can include in there. Say how restoration begins to affect oxygen kinetics, that’s outside this conversation though. It makes sense that if we know that training at these high intensities with the measure of this being the amount of oxygen that somebody is consuming, a little bit ought to give you a little signal and a lot a bit ought to give you a large signal and often times larger signals for adaptation lead to improved adaptation. This is why when we talk about training in general, as volume goes up, fitness goes up because the signal for adaptation is going up and two hours a week of training pales in comparison to 10 hours a week of training and that pales in comparison to 15 or 20 hours a week of training.
What are some of the Foundational Studies that we need to speak toward?
Trevor Connor 12:26
So I think that’s a good segue into talking about some of these key studies and reviews and that’s exactly it. The theory and this is stated in one of the key reviews, this Midgley review from 2006, which says that basically this adaptive stimuli, that is what sparks your body to produce these gains, increases up to VO2 Max. So if you go a little easier, you’re not gonna get as much of a stimuli, you keep increasing intensity up to that VO2 Max power or pace, you’re gonna get more of a stimulus. That’s the theory behind it. I’m not going to necessarily disagree with that. I think there’s a lot of evidence and we’ll go into that physiology. So we’re probably going to really focus on two papers. One is the Midgley review from 2006, which did a review of studies and runners looking at does training time at VO2 Max power, improve their performance, and this was elite runners. Another study that gets referenced a lot now is a turn study from 2016, which used recreational cyclists and had them do kind of a lower intensity right around threshold power intervals and had another group and the intervention was for four weeks. Another group do intervals at a power that seemed to elicit VO2 Max, the quickest and I’ll save you going deep into what that means. So it’s basically a very high intensity interval and then a lower intensity more kind of threshold interval and that study certainly saw greater improvements in both lactate threshold and actually VO2 Max power in the cyclists with the higher intensity intervals. So that one’s quoted a lot. There’s a few others. There’s a Larson study from 2002, which shows that training at that very high intensity, I think this one was what 32nd intervals can produce greater gains in VO2 Max.
Rob Pickels 14:21
Yeah, Trevor, I think that the papers that you’re mentioning are the foundational ones that we need to speak toward because as you said earlier in this episode, many research studies that are coming out recently on workout design and workout effectiveness are very specifically referring to those. So for the sake of this discussion, yeah, let’s let’s keep it confined to these couple and I think that they were so heavy, that it almost is a disservice to bring in even more studies for this conversation.
Trevor Connor 14:51
Let’s dive into this. Let’s take a look at what these have to say and I certainly have something to throw up, but Rob, where do you want to start?
Rob Pickels 15:00
Well, in general, I think that if we describe the research on Midgley, the main purpose of this paper very specifically and I want to get this out there because it frames the rest of the conversation, the title of this paper is, ‘is there an optimal training intensity for enhancing the maximal oxygen uptake of distance runners’. So, one, we’re speaking specifically about runners, that’s great. I guess runners are okay, I get injured every time I run. So maybe this isn’t applicable to me, but the purpose of this paper again, as Trevor mentioned before, is this is trying to improve maximal oxygen uptake and that frames the conversation that majorly has within this paper. It’s a really interesting review. I encourage everybody to read it, it goes through all of the different reasons that VO2 and VO2 Max is a determinant of performance and it describes how you can improve VO2 Max through various measures, they talk about cardiac output, they talk about a VO2 difference and we’re going to be getting into some of those as well, but it also goes very specifically into recommendations for athletes toward the end, but Trevor, I know that you have one very specific issue with this paper and I want to address that one now and that’s down toward the conclusions.
There is No Convincing Evidence that if we Train at a High Percentage, you’ll be able to reach VO2 Max
Trevor Connor 16:22
Here’s my issue. These studies keep getting cited as here’s the evidence for why time at at VO2 Max is such an important metric and when you go into these studies, I am literally right now going to read from them. This is as you said down at the bottom of the Midgley, this is page 129 and says ‘thus far however, there have been no well controlled training studies that support this premise.’ I mean, he says that flat out. Go the turn study from 2016 where he says ‘despite the differences in time at VO2 Max during training sessions between groups, the improvements in VO2 Max are not correlated with time at VO2 Max.’ Thing continues. ‘The absence of correlation between these variables does not allow concluding that higher time at VO2 Max during training sessions leads to superior VO2 Max.’ So these studies are getting cited as the evidence and they quite literally state I just read out of those. You can’t draw these conclusions. You just heard my opinion, but let’s check with Dr. Ronnestad, one of the top researchers in the world, with his thoughts on the validity of using time a VO2 Max.
Trevor Connor 17:29
Can you say if this particular type of interval workout produces more time at VO2 Max in that particular interval workout, this is a better workout? Can you really state that or is it just one metric?
Bent Ronnestad 17:41
Yeah, that’s actually the big challenge because I think these days, there are no convincing evidence that if we train at a high percentage, you’ll be able to reach VO2 Max. If you train the VO2 Max intensity, we then get superior training adaptations because there seems to be a lack of studies actually investigating this and of course, it’s very demanding doing these kinds of studies because then you need to collect a VO2 from every session for an extended period of time to actually look if how important is this time with high VO2. So it’s based on assumptions. That being said, we have me and a lot of very good students performed a nine week intervention where we measured the VO2 during two to three interval sessions per week. So around 500 sessions measured. So I’m really curious and looking at those numbers, but at the moment can’t say anything.
Trevor Connor 18:41
So you said this is all based on an assumption. What do you think is led to this assumption that this time at VO2 Max is so valuable?
Bent Ronnestad 18:49
From my point of view, it was a big review paper published in 1996, which actually looked at the improvement in VO2 Max and whether saw that in the range between 90 and 100% of VO2 Max, they saw the largest improvement in VO2 Max, but they didn’t refer to studies investigating actual oxygen consumption, but the exercise intensity was within this 90 to 100% of the intensity that elicits VO2 Max.
Time at VO2 Max is not the Most Important Training Stimulus for Runners
Rob Pickels 19:20
Yeah, I think and this is where it’s hard right because we’re beginning to bring some interpretation into writing. For me if we actually back up Trevor from where you cited that first Midgley at the very beginning of the conclusion there. It says ‘physiological responses to increasing exercise intensity indicate that training at or near VO2 Max may be the optimal stimulus to enhance the VO2 Max of well trained distance runners.’ I take that as flat out them saying hey, it very well could be this and I think that Trevor this is where you’re struggling. It very well could be that time at VO2 Max it is the thing, the most optimal, but Midgley especially points out further research is therefore required and I think I’m taking these as a little bit more of the optimist. In my mind, I’m saying, hey, time at VO2 Max seems like it’s passing all of these tasks. When we talk about performance studies, it’s making big improvements, but I understand and I do think that this is part of the research process. I don’t know that we’re at the point yet, where we can really complete the study that tells us and maybe tells us the wrong word, but supports the fact that time at VO2 Max is the most important. We have all the foundational research that says it’s very likely the most important. Now a lot of the research that comes out is describing different workouts that improved time at VO2 Max. In my opinion, the next logical step after that is taking the learnings from the workouts that have the best time at VO2 Max, comparing them to other workouts and then having a more direct apples to apples, you know formative research study that really establishes the point
Trevor Connor 21:15
See, I think this is where we disagree because I do agree that doing work at VO2 Max intensity is important. I agree with that. You have to do that work and so there’s a logic to more time at VO2 Max intensity, is probably going to create more of a training stimulus, but I’m still not sold on this is the most important thing. I think there are many factors. I think there’s many different types of forms of training that can produce games and that’s one of the arguments I’m going to get into here. I don’t think they have made strong enough an argument to now say we can conduct studies, where all we’re going to do is look at the time that they spend at VO2 Max and conclude that those intervals are better. I still think you have to stick with the research saying let’s do the intervention. Let’s do it for a certain length of time and see if it actually does produce greater gains and look, I’m gonna cite there’s a study by again, probably going to mispronounce this ag noi from 2021. That did one of these assumptions studies. They have a paragraph where they talk about why they’re going with this assumption and again cite some of the studies that we’re talking about, but then they say flat out ‘a causal association between accumulated time at VO2 Max during a training period and VO2 Max adaptations and trained athletes is still to be determined, although favorable evidence suggests its effectiveness, more supportive evidence confirming this assumption is still lacking.’ So they say flat out we’re gonna go with this assumption, but there isn’t evidence to back this assumption. This is 2021. This is pretty recent study.
Rob Pickels 22:54
Yeah, but in the absence of proof, does that disprove the theory?
Trevor Connor 23:00
No, my issue is going and conducting studies and we’re seeing a lot of these studies now, based on an assumption where you don’t have to prove gains. That’s my issue. So these studies, all these studies that are coming out are not showing that X intervals produce greater gains than Y intervals. They are only saying X intervals produce more time at VO2 Max. Therefore they seem to be better intervals based on an assumption and that’s my issue and even in the Midgley review, he points out an issue with that, a very important issue with that, which is there’s a lot of different ways to get athletes to VO2 Max. So this is something that most researchers understand which is all intervals if you do them long enough, will eventually get you to VO2 Max. So you can do a very long, lower intensity interval and get yourself there. You can do very very short you know 30 second, 20 second, type to body intervals get yourself VO2 Max. So are you then going to say doesn’t matter that they’re completely different, powers very, very different. All we’re going to look at is hey, this one produce more time at VO2 Max, therefore produces greater gains, my argument is going to be that’s an important factor, but they’re hitting very different energy systems. They’re going to produce very different results on the body and to simplify them down to just time at VO2 Max. That’s a mistake.
Rob Pickels 24:28
Yeah, but don’t we need a comparison between intervals to begin to understand the effectiveness?
Trevor Connor 24:34
Yeah, do the intervals for a certain length of time and see the gains that you get.
Rob Pickels 24:39
That takes too long, Trevor? That’s eight or 12 weeks of my season down the tubes.
Trevor Connor 24:46
Which is fair, but you know, that’s the hard work in doing the research and that really, that’s kind of what my argument comes down to is. That’s still what we have to do and to me this is looking for a short cut and just looking at the time and say, Now we don’t have to do that intervention. Now we don’t have to do that 5, 10 week study, we can just see which produces more time a VO2 Max and say that these intervals are better and you know, if you actually read the studies, if you read them carefully, most of them say that. Most of them say you have to be careful, this is based on an assumption. So we can’t necessarily say these intervals are better, but the danger is, a lot of coaches, a lot of people are quickly looking at the title or the just the abstract of the study and going, Oh, these intervals are better.
The Paleo Diet Team 25:33
Let’s pause a minute and hear again from Dr. Ronnestad and his thoughts on why so many researchers are using time at VO2 Max in their studies.
Trevor Connor 25:41
It does seem to be a very recent trend, that there’s been a lot of studies, including a few of yours that are looking at having athletes come in do just a couple sessions where you’re measuring the time at VO2 Max to compare intervals, versus doing the intervention study where you do 5, 6, 7, 8, 9 weeks of a particular interval workout. Just interested in what do you feel has been the the motivation in the research community to do those studies? Ss is there a convenience factor to that where you can at least get some information before you do the intervention study or do they feel this is something that can replace the six to 10 week intervention?
Bent Ronnestad 26:22
I think it’s low hanging fruit. It’s much easier to do it than a long week intervention. So I think that’s probably the most important reason and still, it’s kind of, as you say, kind of hot topic. So you still get the topics, but I think what we really need now is data over prolonged time showing the training effects and I mean, it’s kind of similar with this molecular signaling, acute studies, where we originally thought that, okay, if these signals goes up, then this training method must be the best, but then it doesn’t seem to be so easy and I think maybe that’s the case for this as well, but I think it’s kind of more robust than the molecular signaling stuff and we have some indications that it can give good training adaptations, but it’s also seems to be not the best reliability and reproducibility, so it does change. So you can’t conclude after just one time in the lab.
Is there a Correlation between Time at VO2 Max and Performance Improvements?
Rob Pickels 27:23
So the issue that I have, though, is there are a significant number of interventional studies, whom we’re able to see differences in time at VO2 Max and improvements in exercise performance, but here’s an issue is whether or not that is directly stated within the research. I don’t know that all of these papers have utilized that as the metric that they were trying to define. I think that we can infer this from a lot of the work that Dr. Seiler has done. I know that there’s work by blot at all and there’s other researchers as well. So, in my opinion, if we look at this as the gross recommendation of training intensity training at greater than 90% of VO2 Max is proving superior to other forms of training.
Trevor Connor 28:24
I fully agree with that. Look, these studies have shown these gains. So, some of the studies have done the hard work. The turn study from the get side a lot from 2016. Even though they said flat out, you cannot say that that time of VO2 Max correlates with performance improvements. They did a four week intervention with a lower intensity threshold type interval actually, they use my favorite interval five minute threshold intervals and compared that to 60 second high intensity intervals and showed that the 60 second high intensity intervals produce greater gains in both VO2 Max and threshold power. I do have one issue with that study, but let me cite another couple studies. There’s a few Ronnestad studies from 2014 2015 that did the same sort of thing. He did the hard work, where he did an intervention. Did a lower intensity more threshold type steady interval. Compare that he was often using 30 second intervals in his studies and demonstrated again and again what he called superior improvements.
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Rob Pickels 29:55
The other point I wanted to make about this turns paper is that they do flat out as you said before they do flat out state, there is no correlation in this study between time at VO2 max and the gains that we saw. In my opinion, I feel as though research like this ultimately needs to be repeated because I wonder if something like that as a statistical anomaly and that’s the other side of all of this is there’s just mathematics that need to be done based on statistical power, based on group size and effect size, in that even though significance was not achieved, it doesn’t necessarily mean that it wouldn’t be achieved and I’m not saying that to indicate that we should throw statistics out the window, this study 100% did not find correlation between those two things, but I do wonder if with a different study design or perhaps different subject pool, if we would be able to see that. Now that shifts gears for me to this other point that I want to make.
Trevor Connor 30:52
Hold on before you shift to give validity, absolute validity to what you’re saying, here’s a direct quote of that study, ‘although time at VO2 Max and VO2 Max improvements were not correlated in the present study, likely due to high noise of time at VO2 Max.’ It was a small study group and I fully agree with that. So I mean, yeah, I’m not discounting that there is the possibility, it just hasn’t been proved.
Polarized Training Method and the Three Major Zones of Endurance Workload
Rob Pickels 31:17
Yeah. You know, the direction that I want to shift to though is some of Dr. Seiler’s research which is well known to us and well known to our listeners and that is when Dr. Seiler and others looked at the training principles of endurance athletes, they saw very clearly what became the polarized training method and for those who might be new to this, the polarized training method is essentially breaking workloads into three major zones. Zone one is below the first lactate turn point. Zone Two is between the first lactate turn point and the second lactate turn point and zone three is essentially everything that’s above the second lactate turn point and that’s ultimately called this severe domain as other people would, would refer to it in the research and Dr. Seiler found that the majority of training ought to be below that first lactate turn point, with some training being above the second lactate turn point and if we correlate those values, the second lactate turn point is and we’re making some rough assumptions here, very close to VT2 and VT2 is typically especially in highly trained endurance athletes, at least 75% of VO2 Max. So we’re talking about a relatively narrow window of very, very high intensity and in my opinion, this is evidence that supports very, very high intensities, regardless of the length of time are going to ultimately be more effective than say, the longer interventional studies that you’re suggesting, utilizing these lower workloads.
Trevor Connor 33:02
I love that you brought up the polarized approach because I want to go back again to this Midgley review, which gets referenced again and again and again and again and I probably read this review in college and don’t think I had the full understanding to really get everything in this review and I will tell you rereading this or reading it, but felt like for the first time, this is just a great review, I highly recommend it. It was published in 2006. So that’s before Dr. Seiler really coined the term polarized training, but you see throughout it, he’s bringing up the polarized approach again and again and again and when he gets to his recommendations, even though he never names it, he’s basically recommending a polarized approach and there’s a few things that are really interesting in that review along those lines. First of all, I will say he looked at all the current studies at the time this is again 2006 has been better study since, looking at whether you can say there are gains in VO2 Max and basically said valid inferences cannot be made from the studies due to several methodologies, local limitations. Only one of these studies reported statistical significant increases in VO2 Max. That was really interesting, but while he talked about for as you’re bringing up for high level athletes to see further gains, they probably have to do really high intensity and he actually makes the physiological argument which I think we need to go into. He points out again and again and again that when you look at elite runners, top level runners, they’re actually doing very little high intensities. Matter of fact, he found cases where they were doing no high intensity and we’re favoring the slow and he even says when you get any level of athlete below these elite who have really seen all the gains from going slow. He says in recreational and moderately trained athletes, they’re probably going to see benefits from doing that lower intensity. They’re actually going to see improvements in their VO2 Max without having to really beat themselves up.
Rob Pickels 34:59
Yeah and if I remember right, his moderately trained athletes were about 60 kilometers a week which convert to US distance is, the most important distance in the world, are 36, 37 miles. Yeah, 40 miles a week. So just to put what moderately trained is into perspective here, but and this is a place that I have issue. VO2 Max as a determinant of performance. I don’t necessarily think that we need to improve VO2 Max to improve athletic performance and the difficulty is, we call these VO2 Max intervals and so the assumption or the connection that most people make is VO2 Max intervals must be for improving VO2 Max. If VO2 Max doesn’t improve, they must not be worthwhile.
Trevor Connor 35:48
I was gonna say this to them, but I’m glad you brought that up and many of these studies looking at time at VO2 Max, talk about this producing a superior stimulus to improve VO2 Max, but I agree with you. There’s not a lot of evidence. Let’s pause again and hear one more time for Dr. Ronnestad and his thoughts on the purpose of different interval work.
Rob Pickels 36:08
Is there a danger in coaches reading too much into these studies? Is there a danger in these becoming the only recommendation that are given to athletes for interval prescription?
What’s the Main Aim with the Session, What do you want to Achieve?
Bent Ronnestad 36:20
I think you always need to take into consideration what is the main aim with the session, what do you want to achieve. So if you want to achieve highest possible time with a high VO2, then it could be smart to look at this acute studies, were trying different setups to manipulate and get the high VO2, but if you want to have a session where you want to have a really high power output, for instance, then you should probably design the session in another way and also if you want to give the focus on the threshold and duration of the threshold intensity, then you should design it in another way, but I think what at least from a lot of those studies that we have performed both acute and some shorter training intervention is that having some kind of variation and the benefits of that can be applied both. When you have a threshold focus or you have a VO2 Max focus or you have other focus that’s partly due to the athletes experiencing it kind of easier to perform with the RP is it seems to often be lower when you have this systematic variation. In addition, it can trigger some good signaling pathways for adaptations as well and then think about how the races are performed. They are usually kind of stochastic and changes in power output. So you get both the specificity and you can you can assign the session in terms of what you want to achieve.
Is Focusing Training at VO2 Max still Worthwhile?
Rob Pickels 37:42
I will say that VO2 Max and I don’t know if we’re jumping ahead. So VO2 Max itself is an integrated measure of so many things that are occurring within the body. VO2 Max is ultimately how we measure the result of things like improved capillary density, improved oxidative enzymes and mitochondrial capacity, improve blood parameters, improved AVO2 difference and so I do believe that the training that is, ‘for VO2 Max’ is stressing and improving all of these systems. We know that through the ANPK theory with PCG1 Alpha, that this is one way that we can affect the master regulator and I still believe that focusing training there as opposed to the longer interventional studies at lower intensities, I still believe that focusing training there is worthwhile.
Trevor Connor 38:47
This is where we don’t disagree at all. Again, I am not making the argument that these intervals don’t have a value. I’m making a more subtle argument, which I’ve probably said a bunch of times, but my more subtle argument is making the assumption that time at VO2 Max is the gold standard for saying which intervals are more effective. I just don’t think you can make that logical jump. Is there enough evidence to say doing intervals of this severe intensity are effective? Absolutely and they’re a key part of my coaching, but it’s at particular times and this is another thing that I loved in this Midgley leave review is he actually has a whole table about when to do these intervals. He basically says yeah, once you are at peak fitness, particularly in elite athletes, you’re not going to really see additional gains. So he points out if you go into the study or review it’s page 122, table two, he lists all the different places where doing these intervals are probably going to be the the most effective and what they come down to is two places after a period of D training. So let’s say you’ve been injured and your VO2 Max has come down a bit. You’re gonna see a lot of gains from doing those intervals and I agree with that completely when I I would get injured or one of my athletes who get injured in the season, we had to come back and they had to get on the race form, this is the interval work I would do to get them back on form fast. I wouldn’t be doing threshold work, because the season would be done before they were in shape. The other place is the peak and again, I completely agree with that. I always when I hit my athletes with these type of intervals, I assume it takes about six weeks to see the gains. So I literally count back six weeks from their first key event and that’s when I started doing these intervals.
Rob Pickels 40:30
I struggle with this because of research that Dr. Seiler did, it was 2011 and it was his study where he compared the four by 16. With the four by eight minute with the four by four minute intervals. The four by 16 minute intervals were completed, essentially at VT2. Their sub maximal lactate or their lactate during the performance was about four millimoles. So we know that we’re roughly at the border, what people would traditionally call ‘threshold training’, in my opinion. The four by four minute intervals, were at about 130% of VT2 and in my opinion, you’re getting very close to VO2 Max ‘type efforts’ at that point in time and then there was the four by eight minute intervals that were about 115%. I do think that that is ever so slightly below the 90% VO2 Max that we’re talking about, it’s a little bit hard because he did not measure that. So we kind of have to infer where people are, but in my opinion, I believe that it’s close enough to that 90% that we should lump it in there.
Trevor Connor 41:33
Yeah, those are the four by fours fit and you know, even though you look at the the Ronnestad sets of and several these studies looking at a time of VO2 Max, they tend to favor really short intervals. Like 30 second intervals and they’re often comparing it to the four minute intervals, which are the more traditional VO2 Max intervals.
The Importance of Periodization in Interval Training
Rob Pickels 41:49
But even at this four by eight, I think that we’re like 88% of VO2 Max and so I’m putting that in my high intensity bucket here and there were superior gains and this is seven weeks. So moderately long, I don’t know, I think you would love to see stuff closer to 10 weeks or longer, but we’re getting up there, not just a four week study and there was significantly higher improvements in both the four by eight intervals. Now there was definitely improvement in the threshold intervals without question the four by 16s, but that’s a significantly longer amount of work that people are doing and there was equal improvement in the four by four as there was in the four by 16 and in many measures, they were within a percent or two each other and I very much read into this as in Dr. Seiler states this, the four by four minute intervals were not as effective as the four by eight because four by eight allowed a longer duration at this high intensity and in my opinion that goes directly to support the time at VO2 Max conversation that we’re having today and that is a direct comparison to the threshold intervals that he prescribed, which were the four by 16. Now I’m going to make a leap here and this is a leap and I understand it and I know that you’re gonna be able to poke holes in it, but I’m still going to make it Dr. Seiler followed this up with a study in 2016.
Trevor Connor 42:20
That’s what I was going to bring up which is his periodization.
Rob Pickels 43:17
It’s exactly his periodization paper and in that paper, he compared. He took these exact same intervals, four by 16, four by eight, four by four. Obviously as the duration gets shorter, your intensity has to get higher and he arranged those throughout. If I remember it, it was a 12 week training block. It was four weeks for each. One periodization scheme was increasing intensity, which means you started with the longest intensity sorry, the longest.
Trevor Connor 43:47
Four by 16s, then the four by eights, then the four by four.
Rob Pickels 43:50
Trevor Connor 43:50
And the other one went the other way.
Rob Pickels 43:52
Yeah, then there was the decreasing. You started with the shortest, hardest and you move to the longest and then there was just the mixed. Where you kind of did each one each week and there wasn’t really any periodization. Without question supporting your theory that ‘VO2 Max level workouts’ ought to be done at certain times. The increasing intensity showed superior improvements over this 12 week interventional study were the hardest the VO2 Max ones were done closest to race date, so to say. All three of those interventions, none of those saw improvements as large as the four by eight minute intervals that were done in the 2011 study, which in my opinion suggests, even at these somewhat long interventional studies and I get they could be longer. The pure focus on the VO2 Max level interval is showing superior gains than including some lower intensity intervals in this periodized model that he did in the 2016 study
Trevor Connor 44:57
What I always interpret out of the periodized study was in both, you tend to see the greatest gains in the four by sixteens. I’m not looking at it right now, but the issue was when you started with the four by sixteens, you tended to see that really push athletes into fatigue, the markers of overreach were all there because it was just too big an interval to start out with and then what you saw is they see big gains, but huge markers in these signs of overreach and then they would just kind of plateau. You wouldn’t see that much bigger gains in the four by eights, you wouldn’t see that much bigger gains in the four by fours. The other one, you’d see more gradual increase and then you’d see big gains at the end with the four by sixteens and they’d ultimately end up in about the same place. I’ve always used that study to say to my athletes, we’re gonna go with the increase in intensity through the base season because that first, that increasing starting lower intensity going to higher intensity, to me that seemed to push an athlete into that high fitness, but also danger of overreach very early on and then they just sustained it. Where the other approach seemed to bring them into form right on time for the season.
Rob Pickels 46:08
So in the 2011 study and I do have the data in front of me here, if we compare and I’m just limiting this to the four by 16 and the four by eight minute intervals. If we look at power at VO2 peak as a variable, the four by sixteens saw an 11 Watt improvement, four by eight saw 32 Watt improvement. Power at four millimoles, so roughly power threshold. A 20 watt improvement for four by 16. A 40 Watt improvement for four by eight. Time to exhaustion as a performance measure, 5.3 minutes improvement in four by 16 and an 11 minute, almost a doubling of time to exhaustion for the four by eight minute.
Trevor Connor 46:47
Yeah, I fully agree with you on this. I mean, I use four by eights. Five by fives and four by eights are my default intervals in the base season, but I don’t think these are intervals that maximize time at VO2 Max. I think in these studies that they’re looking at the time at VO2 Max. They would say these are less effective intervals. I also this goes back to my point is it’s about time. I see these intervals produce huge gains in my athletes in their power, but it’s not in four weeks. So I started with the five by fives and then graduate them to the four by eights and to get up to what’s going to be their threshold power for the season. It takes about 12 weeks. Takes a long time.
Rob Pickels 47:27
Maybe you could do it in a shorter amount of time. If you just did the workouts harder, Trevor.
Trevor Connor 47:31
There you go. Well, let’s jump to, I really appreciate it and the Midgley review is he basically said, there isn’t actually any research that states this definitively. So let’s do a thought experiment and let’s look at the physiology. So doing this thought experiment looking at things that can affect VO2 Max, he really pointed to two things and this is getting into that basic physiology of the find in any good textbook. One is cardiac output, which is how much blood your heart can pump per minute. The other one is a VO2 difference. This is basically how much oxygen the muscles can take out of the blood as the blood is passing by. So your heart can pump a ton of blood, but if the muscles can’t take much of the oxygen out, it’s kind of wasted.
Rob Pickels 48:18
The Physiology Description of VO2 Output
Trevor Connor 48:19
Right and I’m gonna fly through this quickly and then you can dive into the details Rob, but he makes some really good arguments in elite athletes for why you need to do really high intensity, which is first of all, when you’re talking about cardiac output, the only thing we can train a stroke volume. How much blood the heart can pump per beat. In recreational athletes stroke volume hits its max at about somewhere 60, 70% potentially even lower. So in a recreational athlete to improve stroke volume they don’t have to go very hard. As a matter of fact, there’s some evidence in lower level athletes that beyond 75% of VO2 Max intensity, you actually see a decrease in stroke volume so there’s a benefit to going slow, but in elite athletes you actually see stroke volume increase in all the way to VO2 Max. So training at VO2 Max intensity, they are going to maximize their stroke volume. So that that’s just physiology and I agree with that. The AVO2 difference, there’s two things that affect that one is computerization. So basically how much you can profuse the muscle with blood. There aren’t a lot of capillaries as muscle doesn’t get much exposure to the blood lot of capillaries, it gets a ton of exposure to the blood and therefore it can take out more oxygen. That again you see that that stimulus for computerization at its peak around VO2 Max power. Likewise, you actually aren’t going to have that much of an impact and slow twitch muscle fibers taken out oxygen, but you can train fast twitch muscle fibers to take out oxygen, particularly those two ways and again, you have to stimulate them and that requires really high intensity.
Rob Pickels 50:00
Yeah, Trevor, I think that that’s really important for us to dive into. For those who aren’t knowledgeable in this area and I don’t want to make this too long, your body can obviously grade force. If you pick up something light, you don’t lift as hard as if you pick up something really heavy. The way that your body does that is muscle fibers can only contract maximally. So to increase the amount of force, you increase the number of muscle fibers that are doing that work for you. A light easy task requires relatively few muscle fibers, the heaviest squat or benchpress you’ve ever done in your life requires all of your muscle fibers. So when we convert this into endurance training, we do have these fast and these slow twitch fibers. Slow twitch fibers are very easy for us to recruit, we tend to use them first at the lower intensities and they fuel or they power our longer activities, but if you want to go faster and ramp up that intensity, you begin to recruit more and more fibers and you bring in more and more type two fibers. Now type two fibers have increasing levels of thresholds before they want to be utilized. So if you’re only training at the 50, 60, 70% of your VO2 Max, you’re leaving a lot of muscle fibers will never ever, ever, ever get recruited. Unless maybe you’re in a very highly fatigued situation, there are some modifiers here, but for the most part, you’re not touching or training those muscle fibers and the only time that you are in an aerobic sense is when you’re at this 90% or greater, then you’ve crossed the stimulus to be recruiting the highest threshold type two fibers and that’s where training them can potentially increase their oxidative capacity, improve the amount of oxygen they’re able to utilize.
Trevor Connor 51:55
So actually, I have a response to that, but I’m going to hold on to it because that my response to that is how I’m going to give my conclusion to this debate.
Rob Pickels 52:03
Trevor Connor 52:03
So hang on to it, but I think we both agree. Again, anybody who’s interested read this review. It’s one of the best reviews I’ve read in a while and I fully agree and I don’t think we’re debating those arguments that he’s making. These three adaptations are knowing adaptations that are very important to endurance athletes and he makes a good argument and there is evidence that very high intensity does improve them. So not arguing at all that this high intensity work doesn’t have benefits and I think that there’s a good case is made there.
Trevor Connor 52:41
Well, Rob, we’re getting towards the hour mark. So unfortunately, I have to close this up. I would love to continue this discussion. I’m actually looking through my notes right now and there’s still a ton of things in here. I’d love to cover and hopefully we get a chance to cover them later, but I think it’s time. Look, I’ll start by saying I don’t think we came up with a definitive answer and this is sort of debates I love this is very nuanced and I think some really good points are made. So why don’t we both just give our overall positions and then we can really let the listeners decide where they land on this and since you pointed out, I’m first in the outline, I guess I will go first. So I’ll start with my response to what you were just saying. So you pointed out the only way to recruit those fast twitch fibers is with really high intensity, but that’s not actually true. There is research showing that if you do long endurance rides in Seiler’s zone one, that you actually see muscle fibers cycling, which is slow twitch muscle fibers will actually fatigue and you’ll start recruiting more and more fibers and even though you’re going at a low intensity, you will start recruiting those type two fibers and because you’re doing low intensity work and you’re recruiting them for a long time, there’s actually an extremely strong adaptive signal on them to start working aerobicly, to increase their oxidative capacity and that’s kind of where I want to go with my conclusion, which is, even though we made a very good case about the physiology. Physiology is remarkably complex. I love studying the complexity of this physiology. There were years where they said, high intensity hits your peripheral adaptation, the low intensity hits your cardiac output or hits your central adaptations. Then we discovered PGC1 Alpha, which you brought up and when actually, all these things kind of hit the PGC1 Alpha pathway and produce the same gains, but Larson had that great review showing that, but they hit it differently and also Holly did this research. Hits it differently and those gains are additive and so my issue here is this is a remarkably complex thing. There’s even the debate can we improve VO2 Max. There is the question of recreational versus elite athletes where you see very different responses and then finally and very importantly, there’s multiple different types of systems that we are trying to adapt. So my issue with this current research is to simplify all that down to greatest gains are accomplished by time at VO2 Max and therefore we don’t have to do the hard work on the research. To see if this actually produces the gains that we predict, all we have to do is look for time at VO2 Max is a very dangerous thing to do because to me, it’s an oversimplification. You’re not looking at what are the different things that it impacts? What are the different interval types and what are the different systems that they adapt? I’m even going to make the point and we brought up that Larson study from 2002, which was another important study that they referenced a lot. Larson says flat out in that study, that training at that high intensity might produce greater gains in VO2 Max power, but he also says it is possible that the improvements in performance after Super maximal HIT could be due to simultaneous enhancement of both aerobic and anaerobic pathways and that’s kind of wearing an elite and the danger of the studies of okay, now time at VO2 Max is really important and we shown that really high intensity produces these gains because I’m now talking from a bit of research and experience as a coach, but I’m also going to point out again how the Midgley review ended, which is talking about recovery and the danger of overtraining. These intervals hit both the aerobic and the anaerobic system and we’ve seen when you really hit that anaerobic system, when you start making fast twitch muscle fibers work aerobicly, that that starts pushing that overreach. There’s only so long that your body can handle that. So again, this is why for me, these are intervals during the season that you only do for a certain length of time because they can fatigue you. So again, to simplify it down to just time a VO2 Max and saying this is best, produces a real danger of not looking at the full effects of the different types of intervals on the athletes, convincing athletes that the super high intensity produce the best gains just because a time of VO2 Max and it’s going to push athletes to do a ton of this work and potentially overreach or even over train themselves and that’s the danger to me.
Rob Pickels 57:21
Yeah, Trevor, you make a lot of great points, I fall back on a couple of tenants, you know myself that I’ve always tried to include in my thought process moving forward and that is I 100% agree that training at these very high intensities, does elicit both aerobic and anaerobic changes within the body and that we can’t necessarily attribute all gains that we have to the aerobic side and that we do have to consider anaerobic is a part of that, but at the same time, I do have significant amount of research supporting that these high intensities show improvements at lower intensity measures such as threshold and whatnot that have little to no anaerobic contribution to them, kind of by definition, but for me, the thing that I really always lean on is Dr. Seiler and the polarized training research that’s been done. When we look retrospectively at the training that high level athletes have done that severe domain, that zone three is important. We know it’s not the only training Trevor and I are 100% agreed on that without question, but there is significant improvement there, but I also do know that Dr. Seiler will say specifically, it doesn’t mean all your workouts have to be in zone three and there was an interview, you can watch that he and I did together. Some of those workouts can be in zone two. That’s okay and this is where the what are the needs of the individual? What are the needs of the event? I do think that zone three severe intensity intervals are the most efficient way to improve performance. When they’re combined with zone one training. I know that they’re not the only way to improve performance and I do also believe that efficiency is sometimes not the thing that you want. If you want to have the durability to do an extremely long event where the limiting factor is more your glycogen stores and your ability to work or consume large amounts of calories. That’s a totally different length of training that you need. That’s huge volumes, long sub threshold intensities. That’s mimicking what you need. So I say all of this with these caveats that we need to be individualizing, but if we are looking at sort of laboratory measures of just purity of performance improvement in a given time, time and time again, severe intensity is seemingly what makes a difference and I do believe that Dr. Seiler’s research and some others looking at say the difference in four by eight minute intervals and four by four minutes intervals, both of those are severe intensity domain. Four by eight was significantly better than four by four. Why? Probably because there was more time and therefore the greater stimulus and so for me, I 100% recognize, I don’t think that there is a perfect study that has put the nail in this coffin without question, but I also in may be choosing to be an optimist as opposed to being skeptical to say, just because that research hasn’t been done yet. That doesn’t mean that this theory isn’t valid. I think that it’s maybe a little bit more of a Schrodinger’s Cat situation, where it may or may not be valid, but we haven’t opened the box yet and that’s going to change the state. I don’t know, that’s a philosophical thing that goes in the wrong direction, but I think at the end of the day, this has been a really fun and a really interesting conversation and I think that it also begs this final statement. People can improve through multiple ways. In even though I think Trevor and I are seemingly opposed to some points in here. In all reality, we’re 85% aligned, and we have slightly different viewpoints on that last 15% and that’s totally fine. That’s the spice of life. That’s the spice of training and we should all be celebrating and incorporating that into the training that we’re doing.
Trevor Connor 1:01:22
I think the place to end this is, I think the the main message of this, go read that and make lead review, that was such a good review, but to the point that you’re bringing up about the polarized model and you need some of that zone three, but you also need a lot of that zone one, there’s a great place in this review towards the end, where after making the case, based on on physiology for why you need to do that time at VO2 Max, he then breaks it into recreational moderately and well trained runners and says, here’s what I recommend to you and for the recreational it’s, you really don’t need the intensity, just go and get the time. For the moderately untrained, it’s you can start adding that intensity, but do it sparingly and then for the elite. It’s yeah, you need that that high intensity to see any sort of improvements even though it’s going to be small, but you need to be careful you do too much you’re going to push them to overreach and that’s basically a great summary of the polarize approach before polarize, the term was coined.
Rob Pickels 1:02:23
Well Trevor, one thing you got to remember is that we’re all elite in our own minds. So take that advice.
The Paleo Diet Team 1:02:30
That was another episode of Fast Talk. Subscribe to Fast Talk wherever you prefer to find your favorite podcast. Be sure to leave us a rating and review. The thoughts and opinions expressed on Fast Talk are those of the individual. As always, we’d love your feedback. Join the conversation at forums.fastalk labs.com to discuss each and every episode, become a member of Fast Laboratories at fasttalklabs.com/join. To become a part of our education and coaching community for Dr. Bent Ronnestad and Trevor Connor. I’m Rob Pickels. Thanks for listening!