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How Much High-Intensity Training Do You Need?

High-intensity training offers many benefits. It also has limitations. We explore just how much HIT work you need to perform at your best.

cyclists racing
Photo: Marcus Spiske on Unsplash

Endurance athletes crave intensity. It’s the closest thing we have to instant gratification: chose an interval, grab the bike (or running shoes, etc.), and head out the door or into the Zwift session. An hour later, the work is done and the feeling of satisfaction washes over you.

What’s problematic is that there are few subjects in endurance sports that are more steeped in mystique or misconceptions. There are as many articles suggesting that you’re not doing enough intensity as there are suggesting you’re doing it the wrong way.

So, in this summary episode of Fast Talk, we dive into the science of HIT and dispel some of those myths, correct some of those misconceptions, and give you a more complete understanding of the benefits and limits of high-intensity training.

We’ll start by discussing energetics and energy systems, as a means to explain why we need HIT to adapt. Then we’ll explore its limitations. Finally, we’ll finish with a discussion of the most effective ways to execute HIT, how precise you need to be in that execution, why consistency matters, and the importance of rest periods.

As with our other summary episodes, we’ve pulled in many poignant thoughts and opinions from other coaches, athletes, and researchers. Today, you’ll hear from pro mountain biker Hannah Finchamp, Dr. Stephen Seiler, Dr. Iñigo San Millán, Jim Miller, Sebastian Weber, and Grant Holicky.

Episode Transcript

Chris Case  00:12

Hey, everyone, welcome to another episode of Fast Talk, your source for the science of endurance performance.


Chris Case  00:18

I’m your host, Chris Case, sitting down today with co-host coach Trevor Connor, and today we’re going to tackle a concept in this summary episode that we’ve been, I can’t believe we haven’t done it before, this idea of how much high-intensity training do you actually need? There are clear benefits. There are limitations. Trevor, tell us a little bit more about the breadth of today’s episode.


Trevor Connor  00:43

I got to admit I’m just excited to be part of the intro. It’s been a long time.


Chris Case  00:47

Hey, you’re here.


Trevor Connor  00:49

I am here.


Chris Case  00:50



Trevor Connor  00:51

I actually really don’t have much to add, that was pretty good.


Chris Case  00:53

Well, thank you.


Trevor Connor  00:55

I’ll say is, yeah, we were surprised when we look back. We’ve touched on high-intensity work many times in the show, but never really done a dedicated here’s what we have seen, here’s what we believe, here are our recommendations on how much high-intensity to do and what are the benefits of it? And also, what are the limitations? So, this has been a summary episode. This is just going to be Chris and me, but we have a real star-studded list of people who we’re going to bring in from past episodes to help make this point.


Chris Case  01:30

Yeah, let me rattle through the list here. We’ve got a lot of people, we’ve got Hannah Finchamp, Olympic caliber mountain bike and gravel racer, she races with the Orange Seal team. We’ve got Dr. Stephen Seiler, someone you’ve heard on the program, hopefully, many times before, he is one of the physiologists that has really popularized the polarized training model. We’ll hear from Kristin Armstrong, a three-time Olympic gold medalist in the time trial, and she has some thoughts she’ll share on interval training. We’ll hear from Coach Grant Holicky of Forever Endurance, someone you’ve hopefully heard on the podcast as well before. We’ll hear from Sebastian Weber, a lead physiologist at INSCYD, and someone who’s coached many, many great World Tour caliber athletes in his day. We’ll hear from Jim Miller, director of performance at USA Cycling. Finally, we’ll hear from Dr. Inigo San Millan, who hopefully you’ve also heard on Fast Talk before, he’s a great physiologist, a great mind in physiology, and just happens to be the coach of, 2020 Tour de France champion. Let’s hear from all of those today on Fast Talk. Hey, Trevor, is there anything else I’ve forgotten?


Trevor Connor  02:42

Wait, do I get to say you get?


Chris Case  02:44

Say it, go for it.


Trevor Connor  02:45

Let’s make you fast.


Chris Case  02:52

Hey, this is Chris Case, did you know you can meet up with other Fast Talk Podcast listeners and discuss today’s episode on our Fast Talk Forum? Our forum is open to anyone who joins Fast Talk Labs through our free listener member level. You can ask follow-up questions about topics you’ve heard on Fast Talk, and sometimes even get responses from the guests we’ve interviewed. Join the conversation, join Fast Talk Labs today at


Chris Case  03:23

So, let’s set the stage. Trevor, tell us a little bit about some of the myths that people have about HIT work.


Myths Surrounding HIT Work

Trevor Connor  03:30

Yeah, I think when you start talking about high-intensity work in training, this is one of the areas where I think there are some of the strongest opinions, some of the biggest misconceptions, and where I really see with athletes this desire to kind of say, here’s what I want, therefore, I’m going to justify why this is what it should be. You kind of see those two directions, one is, if it doesn’t hurt, why would you do it? So, I’m on the bike, I’m going to do high-intensity work all the time. I want my tongue hanging out.


Chris Case  04:05

Yeah, the classic no pain, no gain myth.


Trevor Connor  04:08

Exactly. There’s also that other side of I’m just gonna ride easy and do lots of big volumes all the time, and I think you see these kinds of two sides or these two beliefs. I actually recently read an article by somebody who we know, consider a colleague who basically wrote against bass training, wrote it against long, slow distance, and his argument was, well, if all you’re ever doing as long, slow distance, you’re not going to get sufficient training adaptations. Good point, but whoever said all you should ever be doing on the base season is long slow distance? So, I think one of the messages that we’re going to try to get out here, a message that we’ve been trying to communicate for a long time, and I hope becomes the primary message of the summary episode is, it’s not is HIT work good or bad for you, it’s not more is better, it’s all about balance. It’s about doing the right amount. So, yes, I think these both are myths to say, you’re gonna get fit, never doing high-intensity and just putting in lots of time on the bike. No, you’re gonna go to a race and get killed. Likewise, I think if every time you’re getting on the bike, you’re going and doing something hard, you’re also not going to see the improvements that you expect, and you’re also going to get killed. It is all about balance. So, those are the two myths we want to dispel.


Chris Case  05:41

I would like to clarify here, you will see improvements if you ride your bike more than you did before, and that’s just slow, and you would see improvements as well if all you did was high-intensity to a point. Then you might go over the cliff and start overtraining, etc., and when you say balance, and I know we’re going to get to this, balance does not mean 50% slow, and 50% hard.


Trevor Connor  06:08

That’s the argument that we’re certainly going to make, and that’s why we’ve tended towards the polarized approach. We’re going to ultimately make a lot of that case over the course of this episode that the balance is really 20% high-intensity, and the rest of the time keeping it slow. We’ll make the arguments on the case for why that is.


Chris Case  06:27

You hesitate a little bit when you put 20% on it, because that’s a flexible number. For some it might be 10, for some, it might be 25, throughout the course of the season, it will also change. So, there’s never this is the number that you must hit, and that’s it.


Trevor Connor  06:43

Exactly. That’s the really important point through the season, even within an individual is going to be different. When I’m on the bike in November, I’m probably 95%-5%.


Chris Case  06:52



Trevor Connor  06:53

Because why would I want to be killing myself in November the seasons a long way away. Right now, I’m really working the top-end, I’m probably closer to 30-35 high-intensity, but I don’t want to try to sustain that for very long. So, it can really vary. We’ll make all these cases, but yeah, that’s the kind of starting, I hope we’ve gotten this message across throughout our episodes, but the key here is balance. More is not necessarily better.


Chris Case  07:25

Okay, so let’s actually take a step back here. Often, you’ll see HIT and HIIT. Let’s distinguish between the two, I would assume that there are people out there that think that there’s just an extra “i” in one, and they are the same exact thing. Let’s be specific here.



Trevor Connor  07:49

Sure. I’m going to start by saying we actually looked this up a while ago, and I did find different, I found some really interesting definitions of what they are some pretty crazy stuff, I wish I actually had in front of me, I found a yoga website that had one of the craziest definitions I’ve ever seen.


Chris Case  08:09

A yoga definition of HIT, that’s interesting.


Trevor Connor  08:11

So, understand, there are a lot of different definitions out there. So, I’m going to give you how we think about it. Our definition and I understand that some of you might have seen something different, and that’s fine. But the way I think of it is HIT stands for high-intensity training, and that’s just basically referring to doing training that’s generally at or above your lactate threshold. Now, that can be interval work, but technically, you can think of going out and doing a training race is HIT work, you can think about going out and just hitting the hill really hard as HIT work. So, then you get into the HIIT, which is high-intensity interval training.


Chris Case  08:56

A little bit more specific, supposedly


Trevor Connor  08:58

Right. So, it’s the good old a square is a rectangle, but a rectangle isn’t necessarily a square. So, HIT is broader, and HIIT is more specific. So, it’s one type of high-intensity training. Next question is, what are intervals? So, intervals generally refer to some sort of structured workout where you have a certain length of time that is at intensity with recovery periods and is usually something that you can repeat a certain number of times.


Chris Case  09:32

Well, let’s dive into the topic of benefits. We actually know that high-intensity work is a necessary thing if you’re going to race it has very clear benefits. So, shall we talk about energetics?



Trevor Connor  09:46

Absolutely. My favorite topic.


Chris Case  09:48

Yeah, you went to school, your degree is actually in bioenergetics. Is that correct?


Trevor Connor  09:53



Chris Case  09:53

Professor Connor now, not coach.


Trevor Connor  09:56

Sure, absolutely.


Chris Case  09:57



Trevor Connor  09:58

I like that.


Trevor Connor  09:58

You’re going to call me professor for the rest of the episode?


Chris Case  10:00

Nope. I might call you T-Con or something.


Trevor Connor  10:05

I’m more comfortable with that anyway, so we’ll go with that. We will get the energetics approach. So, I’m going to start by saying, we’re talking about energy systems, and now that I’ve said that, I’m going to say we’re actually not talking about energy systems.


Chris Case  10:20

That’s a simplification, correct?


Trevor Connor  10:22

Right. So, I use the term energy systems all the time, and I have been asked about this through emails. So, when we are talking about training adaptations, and referring to the energy systems, you’re trying to train, it’s a lot, there’s a lot more than that. So, just to name a few, and this is not an exhaustive list by any stretch of the imagination. We’re talking about mitochondrial density, we’re talking about MCT development, we’re talking about lactate clearance, hydrogen ion buffering, vascular polarization, fat oxidization, improving stroke volume, neuromuscular recruitment, muscle fiber conversion,


Chris Case  11:00

Keep going,


Trevor Connor  11:01

Reactive oxygen species buffering, you’re even getting into mental things like mental toughness,


Chris Case  11:06

You’re going to need a banana soon.


Trevor Connor  11:08

I just had a banana before this.


Chris Case  11:09



Trevor Connor  11:10

I’m ready to go, you want me to keep going? The point being, there’s a whole lot of things that you are trying to train, and we do tend to lump all these into this term energy systems. It’s not quite the appropriate term, but it’s just a good simple, you get the concept term, and ultimately, all this is helping you to produce energy to put into the bike to produce power. So, I just wanted to give that qualifier for people who brought that up, yes, you are, right. We are simplifying when we say energy systems, but basically, I’m making my argument for why we’re just going to stick with that simplification.


Chris Case  11:50

It makes sense at times to do that.


Trevor Connor  11:52

Yep. So, with that qualifier, basically, whenever you are training, what you’re trying to do is improve these energy systems. Again, I’m going to skip over this really quickly, because we’ve talked about this a bunch, but the idea here is you need to hit an energy system, you need to do sufficient damage to it to have your body say, I didn’t like that, you hurt me, so I’m going to repair this, but not only am I going to repair it back to where it was before, I’m actually going to make it better, I’m going to make it stronger. That’s really important because it’s about the right level of damage, you do a little bit of damage, your body is going to go, yeah, I got to repair that, but that wasn’t a big deal, so I’m just going to take you right back to where you were before. You do too much damage your body goes, boy, I’m not sure what to do here, so I’m going to try to repair this, but because you keep training, the best I can do is just kind of maintain you. It’s about finding that optimal, enough damage for the body to say, let’s adapt.


Chris Case  12:57

Yeah, that’s super-compensation, it doesn’t come back to the same level, it goes beyond that level and gets you more.


Trevor Connor  13:03

The idea is too much training, you don’t get that. Too little training, you don’t get that. Now, I just rattled off a whole bunch of energy systems, and here’s another thing to think about, which is if you try to train all those energy systems at once you find yourself in a position where you have the one choice of saying, well, I’m going to do enough damage to all of them to get that adaptation, but then the problem is the cumulative damage is huge. Then your body is overwhelmed says, I can’t adapt from this. On the flip side, you can say well, I don’t want to overdo that, so I’m going to try to train all energy systems, but I’m just gonna do a little damage to each one. So, the cumulative damage, the total damage is manageable, but then your body might say, well, you didn’t really do a ton of damage to any energy system, so I’m not really going to train them back right. An example I see of this all the time is with triathletes who try to train all sports equally at all times, they either end up going into that constantly overreached pushing overtraining or they just sort of hid everything and what I hear triathletes complained about all the time is I just don’t seem to be improving. So, when I coach a triathlete, I go, “Look what we are going to do is spend some time, we’re just going to maintain your running, maintain your swimming, and really hit the bike, and once we’ve got that to a point, then we’re going to maintain your bike level, and really hit the running.” I find that more successful, so we’re talking about energy systems, I prefer a similar approach of saying, “Let’s hit a couple of energy systems really hard, get that adaptation,” and then they’re going to kind of be maintained by the work you’re doing to hit other energy systems. This it’s not like training that specific, you can’t really just only hit two energy systems you’re going to you can focus on a couple of energy systems with your interval work, but you’re still going to hit kind of every energy system at once. So, this gets into that, how do you periodize? We’ll talk more about that, but the idea here is you’re trying to hit an energy system, you’re trying to produce an adaptation, and my strong recommendation is if you try to train all energy systems at once as I said, you’re either going to overtrain, or you’re never really going to get any adaptation because you’re not hitting any one energy system hard enough. So, focus on a couple, build them up, then move on to the next ones, and maintain what you built up.


Trevor Connor  15:36

Just to make this point, we did an episode, not that long ago with Hannah Finchamp, who’s a professional mountain biker, and she’s right now on the shortlist for the Olympics. She brought up the danger of trying to hit a whole bunch of systems at once. So, let’s hear what she has to say.


Hannah Finchamp: Dangers of Trying To Hit a Bunch of Systems at Once

Trevor Connor  15:55

When we’re truly talking about unstructured intensity, I think that is when it gets messy because you’re no longer targeting your energy systems, you’re not following a polarized approach, you’re not following a periodized approach, you just can’t mix and match so many energy systems where you’re going for, you know, a 10-second segment, and you’re also going for an hour-long segment, and expect to have the same outcome as someone who’s being very thoughtful in all of their intervals and strategy for their workouts.


Chris Case  16:35

Alright, so we defined HIT and HIIT at the start of the episode. We’ve now defined energetics, let’s bring the two together, what’s the relationship?


Relationship Between HIT and Energetics

Trevor Connor  16:46

So, this gets into the, yes, we need high-intensity training, we need this sort of work, a lot of those energy systems that I just told you about. So, remember, we’re trying to do damage, and do sufficient damage to produce an adaptation. With a lot of those systems, the only way you can actually produce any damage to them is to go hard, you need to do something that’s going to hurt. So, yes, to answer a question, if all you’re ever doing is going out and riding slow, you are going to have some systems that are going to be adapted by that, but those systems that you need to be able to race well, to be able to respond to attacks, to be able to sit there in the field when it’s going really hard up a climb, they can only be trained, they can only be stressed, you can only damage them with intensity.


Trevor Connor  17:40

So, episode 113 with Sebastian Weber, when we were talking about the recovery length in intervals, we started talking a little bit about what are you trying to do with intervals? He brought up some of these systems that you’re trying to hit, some of the things that you’re trying to do with high-intensity such as build up lactate, deplete that fossil creatine, and he was really making the point that you got to go hard, you got to hurt in order to be able to bring about those changes.


Chris Case  18:07

Alright, well, that begs the question, what are the systems or what are the things that can be targeted with this high-intensity training work?


What Can Be Targeted With High-Intensity Work?

Trevor Connor  18:17

So, I’ll start with one that, I’ll say you do need to train with high-intensity, but probably you can also train with some low-intensity, which is that lactate threshold. So, you think about you’re doing a time trial, you’re going up a long climb, you’re gonna be sitting there at that threshold, that’s something you want to train. When they look at what correlates with performance in racing, that’s one of the big ones. So, that’s something you really want to train. That said, they have shown that your aerobic threshold and your lactate or anaerobic threshold, and we’ve already gone into all the different terms for this upper threshold, do tend to move with one another. So, there is some evidence that if you’re doing that lower intensity training close to your aerobic threshold that’s actually going to push both thresholds up. So, that one I put a little bit of an Asterix on.


Chris Case  19:10

Is that true in the opposite direction?


Trevor Connor  19:12

Yes, they do tend to move with one another.


Chris Case  19:15

So, if you increase your anaerobic threshold, you will, so to speak, pull your aerobic threshold up as well?


Trevor Connor  19:23

Theoretically, yes.


Chris Case  19:24

Theoretically, okay. So, you’ve explained this system, lactate threshold system, give me an example, give the listeners out there an example of work to target that system.


Trevor Connor  19:35

The main thing here for me is the length and being steady. You will hear a lot of people that say well, you know your time trialist, I do 40k time trials, so I should go out and do an hour-long interval or a really long interval. My response to that is in a race, you can really motivate yourself and push yourself hard, I think when you’re going out and doing interval work, it’s really hard to do an hour hard enough.


Chris Case  20:00

It’s mentally taxing.


Trevor Connor  20:04

The lengths that I like are on the short-end, five minutes, on the long-end, 10 minutes. I generally don’t prescribe longer than that. The other thing I like about that, and actually, this is where we can throw in a quick quote from Kristin Armstrong is if you do those shorter lengths, you can go a little bit harder. So, you don’t want to be going 140% of threshold, but you can get up 105-110% of threshold where you’re still hitting that energy system, still hitting it actually pretty hard, and might actually get a higher quality interval.


Kristin Armstrong: Training the Duration

Kristin Armstrong  20:42

The number one mistake that a lot of people do is they train the duration. Jim may or may not agree on this, but I’m pretty sure he’ll agree with most things I say. I’m not going to go out, I mean, my Rio time was about 44-minutes, I never trained 44-minutes on my time trial bike, not once I can tell you that, I trained 20-minutes really hard. I was able to expand because of that fitness box that Jim was talking about, my general fitness was so high through road racing, that I can extend that power in that time to 40- minutes, I got to the point where I can extend on training day, a 20-minute time trial to my 40-minutes. So, it was really important to train, I think that a lot of times what I see is when you’re training for a time trial, people are training almost in a zone that’s too long. So, they’re training right at threshold, or sometimes sub-threshold, because they’re not able to keep at 110%, right? Into that VO2 for that long of an interval, so let’s just say somebody does, we’re gonna go out, and we’re gonna do two-by-twenty-minute because you’re racist 40-minutes long. It’s like, why don’t we do one-by-twenty-minutes 110%. So, I feel like there’s a lot of people out there training between 95% and 105%, but when you get up to 110%, and extend that duration to 10-minutes to 15-minutes and eventually to 20-minutes, that is the key zone for time trialing. It is critical because training from 100-105 just isn’t enough.


Chris Case  22:32

Okay, we saw, we’ve just heard from Kristin, who said 105 isn’t enough, she likes to go 110. You’ve talked about going above 100%, but I want to clarify something because there are people out there that are probably a little confused, you’re talking about threshold intervals, to me that says at threshold, but now you’re talking about going above it, and we’ve got an Olympian saying you got to go 10% above it. So, what’s the real answer?


Trevor Connor  22:57

Yeah, good question. This goes back to, you’ve heard me say this before, our bodies aren’t that precise. You don’t ride at 100% of threshold and you’re heading one energy system, and then go to 101% of threshold, and all of a sudden, you’re hitting an entirely different energy system. It is a range, so I think 110% still fits within that range, you’re still basically hitting the same energy system, you just hit it a little bit harder. So, that’s going to produce a little extra stress, it’s going to make your body go, okay, that’s a little outside of my comfort zone, so now I really need to learn how to do this, you just get that little more training stimulus. Now, here’s what really confuses people, because we’ve talked about right at 95% of threshold.


Chris Case  23:42



Trevor Connor  23:43

So, I think it was Neal Henderson who talked about this, he loves to give time trialist, low cadence work at 90-95% of threshold. The reason for that one, there’s a different energy system, and this is very, very specific targeting, unless you’re a time trialist I wouldn’t worry about this. But our ability to clear lactate hits its max, not at threshold, you’re actually on the downside of that curve, it hits its max at about 90-95% of threshold. So, for time trialists is where lactate clearance is everything, doing some training at that point where lactate clearance is maximized, is really, really valuable. So, I know this is really confusing to people.


Trevor Connor  24:27

So, this is some of that, what energy system are you specifically trying to target? So, if you’re trying to improve your ability to ride at threshold, yeah, you want to ride at threshold or a little above, because a little above is going to stress the body and say, well, I’m being forced to sustain power a little above threshold, so I better get my threshold up. But if you’re really just trying to train that clearance, then that 90-95% is really kind of neat trick that used to be a secret that we’re kind of letting out now. The overall intervals here is, I do think they need to be longer for two reasons. One is, it takes time for lactate to plateau, so when you’re at threshold, if you’re truly at threshold lactate should be staying fairly level. When you up to your power, it takes time for lactate to come up and then plateau, you want that. Likewise, it takes time for your aerobics system to kick in, where anaerobic energy is immediate, your aerobics, so the whole Krebs cycle, phosphorylation, the whole electron transport chain, that takes time to ramp up. So, when you do a threshold interval, that first minute or two is kind of a throwaway. So, if you’re trying to do two, three-minute threshold intervals, you’re never really hitting the system you want to hit. So, that’s why I would say minimum of five minutes, and if you’re getting out that 8-10-minutes, it means if you have a 10-minute interval two minutes are a throwaway, you get eight minutes of good quality. So, needs to be a little bit longer, and they need to be steady. When I give that type of interval work, I want them consistent. So, if you’re doing four-by-eights, I don’t want to see the first one if 300 watts and the last one to 240, I want to see the first one at 305 watts and the last one at 295, at most, it’s the biggest drop I want to see.


Trevor Connor  26:23

Now, things that absolutely require high-intensity, anything that involves some form of anaerobic metabolism, you can’t really train at low-intensity, you’re just not going to produce enough of stress. So, you hear people talk all the time about VO2 max, that’s another one that gets an Asterix, they have really shown, if you’re coming off a couch, you’re completely out of shape, you can improve your VO2 max, but very quickly that peaks out and you can’t really change VO2 max.


Chris Case  26:55

In that asterisk, would you say that if you tested yourself in December, and then tested yourself again in April, in the same athlete, obviously, you would see an improvement.


Trevor Connor  27:09

You’ll probably see a bit of an improvement, but there are more of what you’re seeing is you got a little out of shape in the offseason. So, you’re just getting back up to your norm.


Chris Case  27:16

But there’s a ceiling too.


Trevor Connor  27:18

Right. So, it’s more if you look at somebody who’s been training for years and looked at their VO2 max at the peak of each season, it’s probably going to be about the same, you’re not going to see a budge that much. Unfortunately, once you start getting up to my age, you’re just seeing it come down. The other way, obviously, the easy way to improve your VO2 max is because it’s relative to weight, just bring your weight down, it’s going to go up. But the actual oxygen consumption is going to stay about the same,


Trevor Connor  27:45

We’ve got a good short clip from Dr. Seiler from a previous episode, where he talked about the fact that you can’t really improve VO2 max, and the dangers of athletes who think they can and spend a lot of time trying to work it and ultimately end up pushing themselves into an overreach.


Dr. Stephen Seiler: Dangers of Trying To Raise VO2 Max

Dr. Stephen Seiler  28:05

VO2 max is we think fairly much limited by cardiac function, by the heart, by the vasculature, you know how much blood volume you have and things like that. It seems like you know, we’ve tested so many young talented athletes, VO2 max is one of the first physiological parameters for the endurance athlete that actually peaks. So, in the career of an athlete, you may already see that they’re really high for this value at age 18-19. We just tested a couple of guys in our lab last week, and both of them were at 88 ml/kg. I said, look, this is already world-class, but they’re not world-class as cyclists, their lactate power, you know, their threshold power is not high enough, their durability is not good enough, but they’ve got the big engine, and then now they’re going to have to build that out. So, VO2 max tends to peak pretty early, and people tend to overtrain it, that’s where we get into all this interval training. They do a lot of work to keep trying to pound that VO2 max, but it’s just not going to keep climbing. Then you go to these threshold type developments and those take longer because you’re building mitochondria, you’re building capillaries and so forth, efficiency, it seems from the literature, from case studies and so forth, perhaps takes even longer, meaning that we see slow gains in efficiency over time, over several years of training. There’s a case study involving Paula Radcliffe, the marathoner where it looks like that was one of her big changes that led to her world record was she just became more economical as a runner, her VO2 max stabilized, her threshold stabilized, but she got more efficient. So, that seems to be the time course, VO2 max peaks, threshold then peaks pretty soon, and then you get into these durability and efficiency developments. In cycling, those are really important because the races are so long. So, what you see is the athletes slowly extend them, you know the duration that they can be competitive, you know, we’ve talked about this stuff before, and that takes longer.


Chris Case  30:27

Another question that this brings up in my mind and probably listeners out there is okay, so what’s the point of VO2 max training? Is that a misnomer?


What Is the Point of VO2 Training?

Trevor Connor  30:35

You remember we had that long conversation with Sebastian Webber, we mentioned VO2 max intervals, and he’s like, well, what do you mean?


Chris Case  30:40

Right, yes. Playing devil’s advocate, yes.


Trevor Connor  30:44

Because he made a good point, you can’t train VO2 max, why are you calling them VO2 max intervals. I can tell you, when I was up in the center and Canada, we actually called them map intervals, maximum aerobic power.


Trevor Connor  30:56

A more appropriate name.


Trevor Connor  30:57

Probably a little more appropriate, and you’re gonna get my hot take on it. They are done at VO2 max power. So, we took you into a lab, hooked you up to a metabolic cart, and saw what your power was at the point where your oxygen consumption levels off, that’s definition VO2 max. That is the wattage you are targeting with these types of intervals. So, hence they’re called VO2 max intervals. The mistake people make is they hear that and go, oh, well, if I work at this intensity, I’m improving my VO2 max.


Chris Case  31:30

It should be called intervals at VO2 max power.


Trevor Connor  31:35

Exactly, a better way to look at it. That’s why I like the map because it’s maximum aerobic power intervals, you’re doing them at that power. So, what do you have to remember here with these types of intervals is, yes, you are reaching the max of your oxygen consumption, but you do enough of any interval work, you are eventually going to reach the max of your oxygen consumption. So, that’s not necessarily the goal. At these intensities, you are seeing a combination of aerobic energy and anaerobic energy. So, where when you are doing threshold, so that lactate threshold work, you’re really much more focusing on that aerobic system, now you’re getting into that combination of using a lot of both energy systems. So, it’s kind of a hybrid interval, and they just generally really hurt. So, this probably was getting into that, you’re training a lot of different energy systems here.


Chris Case  32:33

It’s interesting, because we have spoken with several really, really good athletes, high caliber Olympians, and they tend to love these things, and maybe that’s because it’s just something that’s hard to do, and they like the confidence boost that they get from completing such a thing, but these are hard, demanding, and people like them, certain people like them, others probably fear them very much.


Trevor Connor  33:00

Yeah, I mean, this is not for this episode, this would probably be a very interesting conversation to have about specifically that type of interval, look at the different energy systems it hits, raise that question of, are you hitting too many energy systems? And when you’re talking about a pro, so think about when you’re a pro at a very high level, you do run into that issue of your body is so well-adapted, you have to really, really hit your body with a lot of stress to produce a further adaptation. So, where I would say to a lower-level athlete, this is going to overload you. With a top-level Pro, I would say, yeah.


Chris Case  33:39

That’s exactly what they need. Otherwise, they won’t get an adaptation.


Trevor Connor  33:43

Right. So, maybe that’s part of why they like it because it’s just a big overload. I think that’s a different conversation. I actually would love to do some research on at some point have that conversation. So, I think the important point that we’re making here is, I’m giving you this list of the different energy systems we’re hitting, and when we think about VO2 max work, I don’t really see that as hitting a specific energy system. I think it’s a bit of a,


Chris Case  34:14

It bridges a few different ones.


Trevor Connor  34:16



Chris Case  34:16

A little bit amorphous.


Chris Case  34:17



Chris Case  34:18

Well, let’s just hear it from Sebastian too, here’s a final thought on VO2 max intervals and why that is a bit of a misnomer.


Sebastian Weber  34:28

Yeah, maybe we should do a podcast, one-hour session about why you call this VO2 max interval.


Trevor Connor  34:36

There’s a whole bunch of terms that just have become the terms that you could really dive into.


Chris Case  34:42

Well, we don’t have to refer to them as such, but let’s just define them as five minutes in length and all out.


Trevor Connor  34:50



Trevor Connor  34:51



Trevor Connor  34:51

So, I’d say four-to-five-minutes and it’s yeah, you should be bleeding from the eyes.


Sebastian Weber: Intervals and Recovery

Sebastian Weber  34:57

Okay, so let’s assume you do that. Let’s talk about why you do that, or maybe you don’t do that, talking about the recovery, right?


Chris Case  35:06



Sebastian Weber  35:07

The issue is here, and that’s the main issue with recovery periods is that you are maxing out different systems, right? You’re maxing out your creatine phosphate stores because those will be depleted at the end of this exercise, you are maxing out your pH levels in terms of decreasing those, you are most likely maxing out your lactate concentration, which you can handle so to speak simplified, you’re maxing out your VO2, obviously like, you know, that’s part of it. The issue with the rest period is that you have now different systems you need to recover, and they have different time kinetics, how long it takes them to recover ends, they have different intensity at which they recover the best. This becomes the complicated thing here so to speak. If your intention is to bring back all systems to full recovery, which is needed if you want to at least try to repeat the same exercise, right? Let’s say if you create a session here to be more precise on what kind of intervals you’re talking about, if you create a session, you say I use the first one full out, and then I use this power as a reference for the other, for the following how many reps you want to do and use this as my reference point and try to hit the same number. If this is what you’re doing, then you need to recover and restore all those different systems, and again, they recover at different durations at different intensities.


Trevor Connor  36:55

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Chris Case  37:28

Alright, let’s move on to anaerobic capacity, VLA Max, what are we talking about here, Trevor?


Anaerobic Capacity vs. VLA Max

Trevor Connor  37:35

So, anaerobic capacity and VLA max get confused, and they are two very different things. One is a capacity, one is a rate. So, anaerobic capacity, the literal definition of this is how much energy, the total energy in Joules, you have above threshold. Now, that in itself is physiologically a little bit wrong, because a lot of that energy does come from aerobics stores, it’s not purely anaerobic stores. The idea is you’re trying to get at just how much energy you have to draw on. If you’re you know, there’s a typical analogy that we use that I think might help you, think about, you’re talking about a matchbox. How many matches do you have before you just can’t go hard anymore? So, that’s your anaerobic capacity.


Chris Case  38:26

Right. You might think of it as a jar or something holding a quantity.


Trevor Connor  38:32



Chris Case  38:33

Whereas, VLA Max is a rate, which means how much if you open up the spigot, how much is pouring out of it?


Trevor Connor  38:39

How big is the top of the jar?


Chris Case  38:42



Trevor Connor  38:43

So, that’s a great analogy and a good way to think of it. So, anaerobic capacity, how big is the jar? VLA Max is how big is the opening of the jar? So, you could have a big jar, but if you have really tiny opening, you just can’t pour out very much.


Chris Case  38:59

Right, Right.


Trevor Connor  39:01

So, you can keep responding to things you just can’t respond to well. Or you can be like a big sprinter who’s got a pretty big jar, but as a really big opening, just flip it over and dump it all out at once, but then you’ve got nothing left.


Chris Case  39:15

Yeah, just once almost, one match.


Trevor Connor  39:18

So, good ways to think about it. Anaerobic capacity, so the term used in the literature is watt prime. This was something that actually Dr. Tabata was studying was watt prime, and he was trying to figure out how to deplete it, so he could study it. So actually, when he came up with Tabata style interval, he wasn’t trying to come up with a workout, he was trying to come up with a way to study this capacity. He found if he asked athletes to just go really hard for five, six minutes until they’re depleted that was just too hard and they couldn’t do it, if he gave them really hard efforts with frequent, short recoveries, the recoveries weren’t really enough to restore any sort of anaerobic store, energy stores, so you could very effectively deplete the swap prime. So, that is the origins of the Tabata style interval, and they are a very effective interval for improving your anaerobic capacity. So, this is your 20/10s was the original, so 20 seconds all out, 10 seconds, easy, 20 seconds all out, and you repeat that from anywhere from five to eight minutes, and it’s a good killer workout. A lot of variations on this, pros actually seem to be tending more towards the 40/20, which sounds absolutely miserable to me, but then I used to do a one-minute, 30 seconds, which really hurt. My favorite even though it’s not a true Tabata is actually 15/15.


Building Sprint Power

Chris Case  40:50

All right, moving on, let’s talk about sprints.


Trevor Connor  40:54

So, building sprint power is kind of its own beast, and this is probably the thing that is the most genetic, either got it or you don’t.


Chris Case  41:05

And you don’t got it.


Trevor Connor  41:06

I don’t got it, and I go out and do a whole lot of sprint work. I think I’ve improved my sprint power by about 100 watts. You got it or you don’t, I know other people who have never done a sprint interval in their life and put out 1600 watts.


Chris Case  41:21



Trevor Connor  41:21

So, it’s still a good thing to train there is research that shows that working on your sprint drains a lot of energy systems, though, I really want to warn people about putting too much faith in that, because most of that research was done on people coming off the couch, and remember, you take somebody off the couch, you have them do anything, they’re going to get fitter because they haven’t been doing anything. If you are well-trained cyclists, you’re not gonna see quite such a wonderful result from a single interval workout. Sprints are still valuable, and they’re going to hit a lot of those upper-end systems, improve that peak power and the trick to these is they need to be all out, and you need long rests. So, I generally don’t prescribe anything over 20 seconds, I’ve seen recent research saying in many ways five to six seconds can be better. So, don’t think you have to sit there and sprint for a minute, that’s no longer a sprint. But you watch a good track sprinter they will do a sprint, then they will get off the bike.


Chris Case  42:29

Yeah, sit there basically.


Trevor Connor  42:31

And lie down.


Chris Case  42:32



Trevor Connor  42:33

For minutes. So, I’m not necessarily suggesting that, but I can tell you when I do sprint work I do it on a climb, as soon as I finish the sprint I turn around I let the bike roll very slowly down the hill, and by that I mean I have my brakes on to maximize the length of time before I have to start pedaling, and ideally, in between the sprints, I do 10-15 seconds at most of very easy pedaling.


Chris Case  42:58

This may be splitting hairs do you start the sprint from a slow speed as possible from a standing start? Does it really matter?


Trevor Connor  43:08

I don’t think it really matters, because you’re trying to hit power. I roll into it slowly, because I’m doing it on, this the other is I use the hill I’m doing on a road with cars and when you’re all out sprinting you don’t have as good control of the bike as you would have in other interval work, if a car comes, if something happens, because you’re rocking that bike all over the place you’re hurting, you’re seeing red, and there is a danger in the interval in the workout. So, I like to do it on a climb because I never get very fast, and I want to be able to put out that big power without hitting that highest speed just to keep it safer.


Chris Case  43:47

And how many sprints would you do in one session?


Trevor Connor  43:52

So, if I’m doing the 20 seconds, and I’ve heard people, so bear in mind I’m not a good sprinter so these don’t hurt me the way they hurt or other people, and the first athlete I coached who was a good sprinter, I gave these to him and he couldn’t get through the workout. A good sprinter will tear themselves apart, so I have learned with a good sprinter I will give them actually less and I will give them shorter sprints. If you’re a time trialist like me, you just don’t do as much damage. So, I’ll do sets of eight repeats of 20-second sprints.


Chris Case  44:26



Trevor Connor  44:26

And do two sets and it hurts.


Chris Case  44:29

But for a sprinter, they might do 5-10 seconds sprints or something like that?


Trevor Connor  44:33

Keep it shorter. It’d be interesting what other people say here but yeah, I have found you take a pure sprinter, give them the workout I do, and they can’t walk for the next five days, because they can tear themselves apart.


Chris Case  44:45



Trevor Connor  44:46

I mean, you experienced this. You did the one-run sprint.


Chris Case  44:49

Yeah, yeah, different contexts, really. But yeah, if you’re not used to this, and you just go out there and especially if you’re not warmed up, there’s danger there that you could do damage that will take a while to repair.


Trevor Connor  45:05

Not as dangerous on the bike, but I still have seen athletes destroy themselves down to a hard sprint workout on the bike.


Chris Case  45:12

Alright, let’s turn our attention to sustainable power. What are some practical applications here, what are some workouts we can talk about?


Sustainable Power

Trevor Connor  45:22

Sustainable power covers a lot, and this is one that you can actually train with low-intensity. So, going out and doing those long rides at aerobic threshold is a sustainability workout, and actually, a very valuable and important one that’s low-intensity. When I think about sustainable doing high-intensity work, it’s that ability to repeat intervals again and again, so it’s back to that doing the hill repeats, but hitting the same time, it’s training your body to be able to keep doing it repeatedly. This goes back to what you hear pros say all the time, it’s not how hard you can do the first climb, it’s how hard you can do the last climb after four hours of racing. So, I’m not sure exactly what energy system you would call that I just call it sustainability, but that ability, when you are hurting to keep putting out the same power is really critical for racing.


Chris Case  46:18

Do you ever suggest to a rider to target this type of ability, do three hours of riding or four hours of riding, it doesn’t have to be climbing it could be flat, and not going super hard, but then throw in a set of intervals at the end of that ride and focus on consistency there?


Trevor Connor  46:50

I don’t give that all the time, because you’re not obviously going to do the intervals with this the same sort of quality you would do if you were fresh. I do think as you’re getting closer to the season, and you’re trying to train some of these other systems, particularly that ability to go hard when you’re already tired, is really important. So, yeah, I will give some of that. I love to give an athlete that four-to-six-hour ride and say at the end of it, I want you to go and hit a climb and hit it hard for 20-30 minutes. So, you can also do that with you know, it’s easy for us here because we got 30-minute climbs. If I have somebody in an area where they don’t have that, yeah, I’ll give them some repeats that I want them to do towards the end of that ride, knowing they’re not going to do it with the same quality, but that’s not what we’re trying to train, what we’re trying to train is that sustainability that repeatability.


Chris Case  47:37

So, we’ve established that high-intensity training is beneficial, it has a lot of benefits, you can’t race well without it, however, at the start of the program, we talked about this idea of balance, it must be balanced, there is a limit to what you should do. Let’s talk about that. Why are there limits here?


Limits to High-Intensity Training

Trevor Connor  48:02

This is actually getting into one of those things that you know I love to talk about, there are a couple of studies that really dive into this that I absolutely love, and I probably referenced a bunch of times. So, there’s actually one that was written by Dr. Kofi and Dr. Holley, that really goes into the physiology of all this, and then there’s a great review by Dr. Larson that addresses his exact same question, how much high-intensity versus how much volume? I love the Dr. Larson study because he starts by quoting a bunch of research that shows all these benefits of high-intensity and no benefits to low volume and then says, but then why do pros do so much volume? Then provides his explanation. All this really leads to why we have landed on this polarized approach, which is that kind of a touch of high-intensity about 15-20% high-intensity and the rest low volume, because of this need for balance. So, let’s go into this. We’ll do some of the physiology behind this, and really hope that this explains why, yes, you absolutely need high-intensity work, but why more is not better. Even if you’re somebody who’s only training six to eight hours a week. More is not necessarily better.


Chris Case  49:20

Right. We have again touched upon this several places before, fairly recently as well in the two-a-days episode, I think we touched upon this very subject, but let’s dive into this maybe a little bit deeper than we have before. Talk about the fact that high-intensity work happens fast the adaptations that you’re seeking happen fast, and they peak out quickly. What’s that all about? How long does that take?


Trevor Connor  49:49

So, before I can answer that, let’s go back to one of my favorite terms.


Chris Case  49:53

Uh oh, I hear it, PGC-1 alpha.


Adaptations in High-Intensity Work

Trevor Connor  49:57

So, let’s talk about this. So PGC-1 alpha, how many episodes have we talked about this? This is this master regulator, when you look at most of the adaptations the favorable adaptations that you get from endurance work from endurance training that as a cyclist, as a runner, as somebody involved in endurance sport, you want to see these adaptations. It is PGC-1 alpha that is acting as a signaling molecule to make these things happen. So, it is the master regulator, but there are four pathways that activate PGC-1 alpha. I’m not going to go into two of them, I’m really just going to cover the two important ones here. One is this calcium calmodulin kinase pathway. The other one is the AMPK pathway. So, the two key pathways that we’re going to talk about today that activates this PGC-1 alpha are the calcium calmodulin pathway, so we’ll call that the CAMK, and the other one is the adenosine monophosphate kinase pathway or the AMPK pathway. So, what you tend to see is that long, slow volume work, just getting the time on the bike easy intensity, tends to activate the CAMK pathway. High-intensity tends to activate PGC-1 alpha more through the AMPK pathway. This is important because what is been showing in the research is that well, they both activate PGC-1 alpha, the impact is different. So, AMPK, that pathway that’s activated by high-intensity work tends to produce results very quickly, we’re talking weeks. The issue is it also tends to plateau very quickly, so you can produce rapid gains, but you’re going to see those gains level off, and you can keep hitting yourself with high-intensity, all you’re really doing is just maintaining form at that point.


Chris Case  52:10

I think we’re going to get to this, but I want to have you clarify one thing you say that this stuff, this high-intensity work, through this pathway, the AMPK pathway works in a matter of weeks, is that one session per week for four weeks is all you need? Or my jumping too far ahead, and we’ll get to that later?


Trevor Connor  52:35

I think we’ll probably cover that more later, but it’s a good question, and my answer is it depends on the type of high-intensity work. What I have seen as a trend is the higher the intensity, the more rapid the gains, and the more rapid the plateau. So, for example, when I give athletes pure lactate threshold work, I want to have at least eight weeks often 12-to-14-weeks to see gains. When I’m giving them that more anaerobic capacity type work, so let’s say Tabata type intervals, I’ve seen a lot of research and I’ve seen this from experience, it takes about six to eight sessions total. When I’m giving sprint work, boy, you see rapid gains quickly, but I might only give dedicated sprint intervals two, three weeks at most.


Chris Case  53:22



Trevor Connor  53:23

So, the higher the intensity, the more rapid the gains, but the shorter you want to do that type of work. That’s at least been my experience, and I’ve certainly seen some research to back that up. So, the key thing here, though, being that AMPK, quick adaptations, also quick to plateau. The calcium calmodulin pathway takes a long time to see the gains,


Chris Case  53:47



Trevor Connor  53:48

Months to years, right. But it doesn’t seem to plateau nearly the same way. So, that’s where you will see gains year to year, and you’ll keep getting stronger as an athlete, but you have to be patient and want to see those gains. That’s the hard part because everybody goes and does the high-intensity intervals, and two weeks later, they’re significantly stronger, they go, “Why wouldn’t I do this all the time?” I remember my first year at the center up in Victoria, Shang tore me apart with the low-intensity stuff during these 36-hour training camps, and tons of volume that just had me completely fatigued, and he had warned me about this, but I had no idea what it was gonna be like, I went into my first race that spring and was no better than I was the previous year, if not because I was so fatigued maybe a little bit worse, that was discouraging. I can see a lot of athletes going and doing this type of work and go, “I’m killing myself, look at all the sacrifices I’m making,” and then get to that first raise and go, “What?”


Chris Case  54:54

Yeah, they might question why they’re doing it at all. They have to have some patience, the long-term view is what’s necessary when you’re trying to make the gains that only come about through this pathway.


Trevor Connor  55:07

What I can tell you from my own experience was, yeah, that year was a rough year. When I met with Shang right when I came to the center, I told him my goals, and he went, “Great, two years from now.” I went, “No, next year”, and he’s like, “No, two years,” and I ignored him. He was dead right, that first year, I killed myself, I did a ton of training, and it was a disappointing year because I wasn’t ready for this. Following year, I was twice the athlete.


Chris Case  55:32



Trevor Connor  55:33

Just at a level that, for me, shocked me. So, that’s what you need to be aware of, and that is always that temptation, and why there’s a lot of people who go, “I just want to do high-intensity all the time, because look at how quickly I’m improving.” Just be aware of the fact that, yeah, you’re improving quickly, you’re gonna plateau.


Chris Case  55:53



Trevor Connor  55:53

And if that’s all you’re ever doing, don’t be surprised at year, after year, after year, after year, you’re just the same level.


Chris Case  56:01

In the context of an endurance sport, it’s equivalent to instant gratification, right? It’s not instant, but it’s closer to it than the other gains you’ll see from the long, slow distance work.


Trevor Connor  56:17

Yeah. If you know this stuff, you can cheat a little bit and take advantage of some of that. I have a lot of years where I would do a ton of base training, come into the season, have really no race form, have some races coming up where I need to do decently, just go to three sprint workouts, and then yeah, I’m not on peak race form, but it’s amazing, just three sprint workouts, I go from pure base form, to not bad racing form.


Chris Case  56:44

Yeah. So, we’ve talked about these two distinct pathways. What’s the explanation for why one sort of ramps up quickly and plateaus and the other takes such a long time to develop?


Trevor Connor  56:57

I’ve had a theory for why this is for a long time, and I’ve now seen some research to back this, and I’ve heard some people say this as well. The short version of my theory is, I believe that a lot of these adaptations, these rapid adaptations, that you see from the high-intensity, are more biochemical in nature, and your body can produce biochemical changes really rapidly. I think those other changes that take years, months to years, are more structural. So, let me give you a quick example, one of the biggest adaptations that we see in endurance athletes, is an improvement in stroke volume. So, that’s how much blood your heart can pump per beat. There are two ways to improve stroke volume one, the structural, is to actually increase the size of your left ventricle, and there’s a great old study that looked at Tour de France athletes, and sure enough, found they had much larger, a lot of them have much larger left ventricles than your average person. That takes a long time to remodel your heart like that. Another way to improve stroke volume is just simply to increase your blood volume. So, think of it as a big garden hose. If you push more water, if you have more water to push through that hose, it’s going to come out more rapidly. So, you’re going to get more blood coming out per beat just because of that increased pressure. That’s biochemical that can happen really rapidly. So, the issue is, with biochemical is there a stressor on the body, they appear quickly, they can also disappear quickly. Make structural changes, I did read a study a couple of years ago, where they looked at cyclists who had that increased size in their left ventricle, even 10 years after quitting cycling, they still had that remodeling.


Chris Case  58:49

We actually have spoken to Dr. Seiler about this very subject, and he’s got some thoughts that we’ll share right now. He refers to these adaptations you see from the high-intensity work as this fresh fruit, comes along nicely, comes along quickly, but can spoil very quickly, I think is the point about this fresh fruit, it’s ripe, but it doesn’t stay that way for long it starts to rot. So, let’s hear from him about those gains.


Dr. Stephen Seiler: Comparing High-Intensity Work Adaptations to Fresh Fruit

Dr. Stephen Seiler  59:22

The bottom line is, is that yeah, when we increase the intensity for the intervals, you can use a minute, 90-seconds and so forth, then you can use that same idea, and go as hard as you can, or you know, you end up around maybe 170% of functional threshold power, that was what Tabata used. If you go all out 30-seconds here, maybe at 200% of FTP, these kinds of workouts will give you a little extra signal for that anaerobic work capacity stimulate, but I would say they’re not the best type of interval session for the aerobic stimulus. If I’m 6-to-60-minute range or even, you know, it’s very typical, even if we’re talking about a five-hour event like the Tour of Flanders, it comes often down to that last hour, right? Between 6-and-60-minutes is often where things happen, and you want to prepare your athlete to be able to produce a large average power in that duration range. In that duration range, it’s much more important to have a big VO2, a big aerobic capacity, than it is to increase your anaerobic capacity by a few percent, and the cost of doing those anaerobic workouts is high. My argument to people is sure, if you’re going to be competing for you know, or you’re going to be doing a competition where you need to be able to really dig deep on the anaerobic side, then let’s top off the anaerobic capacity tank with a cycle, a three or four-week cycle of these anaerobic intervals, could be Tabata, could be four-to-six-times a minute, 40, you know, 100 seconds, with 60-second rest or 70-second rest. There are different ways to do it, but I want on those workouts, I want the athlete to basically slowly get cooked, I want them to build up a high, a low pH, and high blood lactate. I want to do it under control, you know, I don’t want them to start too hard. I want them to collect some minutes. So, for these anaerobic sessions, we might be collecting six-to-10 total minutes of anaerobic work. The typical Tabata workout is three times, four minutes, basically, 20-10 times eight, that’s four minutes of work, you do three times, that’s 12 total minutes of which is eight minutes of work. So, that’s a typical anaerobic capacity session, and if you do that for three or four weeks, you’ll get a bump in your AWC, you’ll get a maybe a 10% increase in the power you’re able to average for that kind of a workout. That may translate from a six-minute race to a couple of seconds of improvement in your time. Definitely, if I’m an athlete, and I’m in that, you know, situation, or if I’m a sprinter in a long race, then I’m going to be willing to invest some workouts to top off that tank, but we have to look, it’s fresh fruit. Those adaptations cost a lot to achieve, because you’ve really got to stress the system, and they disappear fairly quickly.


Trevor Connor  1:02:56



Dr. Stephen Seiler  1:02:58

As a coach, I wouldn’t use really high-intensity anaerobic workouts regularly, if I’m not in need of that peak anaerobic capacity, because the cost of maintaining that versus you know, the effect that you get is pretty high, or very high. Use those 100 hard sessions in the course of a year, that we’d want to do some hard thinking about how often do I need to do those really severe anaerobic sessions?


Chris Case  1:03:35

I think it’s worth mentioning as well, when we’re talking about this high-intensity work and why it tends to plateau quickly, and we talked about going over the edge of that ripe fruit spoiling, what we’re getting at is the amount of autonomic stress that it causes and what that can lead to. So, Trevor, do you want to explain a little bit more what we mean by that?


Autonomic Stress

Trevor Connor  1:03:59

Yes. So, Dr. Larson has mentioned this, and actually, Dr. Seiler did a whole paper on this concept of autonomic stress. Let me take a quick step back and say we’ve been talking about you need to produce stress in order to get adaptations. There’s good stress and there’s bad stress, and autonomic stress is not the type that produces adaptations. Autonomic stress is the type of stress that you need to recover from or it’s going to push you into that overreached, and if you really push it, into an overtrained state. So, this is something you want to flirt with, you don’t want to overdo. When you are going slow and easy, you’re producing no autonomic stress, it’s quite literally like an on-off switch. Once you go above a certain intensity, you start generating that autonomic stress and when you’ve generated enough, then you need recovery. You need that true recovery to let that come back down, get that heart rate variability back up, get your body back into balance. So, that is a big danger, one of the big dangers of doing too much high-intensity work is all you’re doing is more, and more, and more autonomic stress and you are going to push yourself into an overtrained state. So, what that means is, and again, we’re kind of harping on Dr. Seiler, hope you’re listening, hope you’re enjoying this. We’ll bring in some other people, we got some great quotes from Dr. San Millan and from Grant Holicky, that we’ll talk about in a minute. With the high-intensity training, what you see is two sessions per week produce a lot of gains, and it gives you enough time that you can recover and then hit your body hard again, three seems to produce no additional gains, and when you start doing more than three in a week, that’s when you start pushing that very quickly into the overreaching and overtrained state.


Trevor Connor  1:06:04

So, there are really two reasons why we’re saying HIT work is fantastic, but you need to limit it. One is because its gains are rapid, but they plateau, and the other one is because if you start doing too much, and this applies, even people just training six hours a week if you start doing too much, you’re gonna start overloading your body and start pushing into an overtrained state.


Trevor Connor  1:06:27

So, this is one of my favorite quotes, even though Grant actually isn’t talking specifically about doing too much HIT work, I’ve had this conversation with him, but it’s kind of the same effect, he talks about ending up in this kind of mid-range where you’re always sort of going hard, not ever really going easy or ever really going really hard, and when you do too much HIT work, that’s also what happens too. So, let’s hear what he has to say.


Grant Holicky: Medium Place in Training

Grant Holicky  1:06:59

So, the one that jumps out of me always is making the easy too hard and making the hard not hard enough. Training is about working the edges of the system, base training is that percentage of wattage or heart rate, or however, you happen to be describing it, or perceived effort, base training is the foundation of what we’re doing as an athlete, you can do that base training harder, and frankly, one of the really interesting points is, shown in many in several studies, base training, which is a little bit easier, and tempo training, which is that no man’s land below a threshold, actually, you’re going to give you a similar physiological response, they both have a similar effect on threshold power, they both have a similar effect on VO2 max power, all of those things, just one of them makes you more tired than the other one makes you. So, the more time we spend at tempo, the more time we spend in that no man’s land, that’s going to zap the legs, that’s going to zap the body, now when we turn around on Wednesday, and it’s time to really just rail those threshold efforts or rail those VO2 max efforts, we tend to not have as much left in the legs. So, the hard training gets diminished down a little bit, the easy training gets lifted up a little bit, and we live in that world, as Neal, my partner at Apex Coaching describes this, we live in moderato, we live in that medium place, and we’re not going to get that return out of that medium place, make your hard efforts super hard, and make your base training in your easy days at base or super easy.


Chris Case  1:08:37

Let’s turn our attention now to more of the execution side of things, and we’ve talked about the different types of work you can do, these different categories that there are, and we segmented it quite a bit. However, there are other opinions out there, and at one point, in the in the recent past, we talked to Jim Miller, coach at USA Cycling. He often refers to these three big buckets that he throws things into, so it’s probably worth sharing that clip now.


Jim Miller: The Three Buckets of Training Intervals

Jim Miller  1:09:12

I tend to think that our body is how we define these energy systems and specifically intervals, is not that fine, we’re not that sophisticated. When you tell somebody 280, the body really doesn’t know the difference between 278, 275, 283, etc. So, I tend to dump things into bigger buckets, change their intervals up accordingly. I do take the threshold interval, and I like to do it a couple of ways. I do long threshold intervals 15-minutes, 10-15-minutes when we’re building fitness, but then when we start to get to race season then I think that the broken intervals, the three on, one-off, but you doing 15-minutes of it tends to elicit a little bit different response, you end up with higher power output, it’s a harder interval, and I think for your bang for your buck in racing to get more out of that.


Chris Case  1:10:19

So, Trevor, to follow up on what Jim just said, would you share his opinion? How precise do you need to be? What are the buckets that these things fall into? Are you segmenting it a bit more than what he does?


Trevor Connor  1:10:32

Well, I’m really glad we played that clip from Jim Miller first because you’re about to get another one of my hot takes, but now I can blame it on Jim. I will give you my bias, which is I get questions all the time, these things like, well, if the recovery is 20-seconds versus 25-seconds, or if I do this at 97%, of threshold versus 99%, a threshold, and those little nuances, you know, doesn’t that make a big difference in the training? Well, I do believe that proper execution is important, I don’t think it makes that big a difference in terms of what energy systems you’re hitting. Now, this is where I’m really going to have to thread the needle, because it does sound like I’m saying, well just go do whatever, and don’t care about the execution, because it all kind of hits the same thing. I’m not going to quite go that far. I think when you are doing intervals, you need to execute them very effectively. But what I am going to say is there’s a lot of ways to skin the cat, and when people say well does, you know this particular type of Tabata versus that particular type of Tabata, they have very different energy systems, my answer tends to be not really, maybe a little, but when I pick intervals for my athletes, I tend to just go well, we really want to do some anaerobic capacity work, so I’m going to give you something that’s short, and what I’m actually going to give you is a couple of options, see which one gets you motivated to go out and go on the bike and go really hard, and then that’s the one we’re gonna do. It’s not gonna be, oh, no, you’re doing 30/30s is not 2010s, now, you’re gonna ruin your whole season. Yes, I’ve seen research that shows they have slightly different impacts on you, but if I give you 20/10s, and you go, I hate this, and I don’t want to do it, and you kind of give it a half-hearted execution versus boy, I love those 3030s that gets me out there every day. Let’s go with the 30/30s. So, this is that threading the needle a little bit, but yes, generally, we gave earlier those overall categories. I think within those categories, you’re going to find they’re all kind of hitting the same system. As I said, you can find all this research on this one does versus that one, but at the end of the day, there’s the practical going out, what can you do? What do you enjoy doing? They’re mostly hitting the same systems, so don’t stress that too much.


Chris Case  1:13:15

So, what you’re saying is that you’d rather a person choose a workout that they actually like, will commit to, will execute well, and will come out feeling confident that they did it, even if it isn’t the quote, unquote, perfect workout for what they’re trying to gain, versus choosing something that is the quote, unquote, the perfect one, which doesn’t really exist, and they hate it, and they kind of are sloppy about it, and they come out, just grumbling about it.


Psychology of Interval Training

Trevor Connor  1:13:48

Right. So, let me give you an example. I actually just had this conversation with one of our listeners, literally the example I just gave you. They were comparing 30/30s to 20/10s, and really passionately making this argument that they train very different systems and which do I need to do in order to accomplish, they were giving me very detailed here’s what I’m trying to hit, here’s what I’m trying to do. Here’s my argument that I’ll make to almost any athlete, go out, do 30/30, do a month-and-a-half of 30/30, then later in the season, do a month-and-a-half of 20/10s, then go do some races and try to show me you can tell the difference between what impact it has in your racing. So, we put you in the lab, put you on a metabolic cart, and measure the differences, we’d probably see some minor differences. But when it comes to racing, you’re gonna be really hard-pressed to say boy, those 30/30s destroyed my racing, and those 20/10s we’re just the miracle cure. More of what you’re going to see, my point being, if you’re going out and hating the 20/10s and loving the 30/30s, you’re probably going to race better after is the 30/30s because they’re motivating, you’re going to do them better, you’re going to be enjoying your riding more, and overall, it’s going to make you a better race.


Chris Case  1:15:08

Right. Yeah, the psychology of interval training, something that people don’t often think about.


Trevor Connor  1:15:15

Right. So, I fully agree with Jim Miller that you kind of dump all this stuff into buckets, and as long as you are picking from the right bucket, I personally don’t get that worked up over which specific interval you’re picking, because I think that’s where you’re getting into the, yes, theoretically, and again, if we had you in the lab, we could see differences, but out in the road, in the real world, that just doesn’t play out the same way.


Chris Case  1:15:45

Well, one thing that I think is worth mentioning here, and we did an entire episode on it, it was a really good one with Sebastian Weber, is there are significant differences based around the recovery between intervals that can change the adaptations you get from any given interval workout.


Trevor Connor  1:16:03

Yes. So, the classic example there is the original Tabata was 20-seconds all out, 10- seconds recovery, and you just keep repeating that. Now, let’s say you know, I’m gonna prescribe a completely different workout, with the only difference being the recovery length, and this is now going to be a pure sprint workout. So, again, 20-seconds all out, but two-to-three-minute recoveries without pedaling, gonna have a very different impact on your body, because, with that couple minutes of recovery, you’re going to completely restore your phosphocreatine, you’re going to basically recharge that whole anaerobic system, to be able to go all out again. The point of the 20/10s is there is not enough time to recharge your anaerobic energy stores. So, even though you’re going all out, anaerobic capacity, as it was designed, is being depleted. So, very different workouts, and really, the only difference in the prescription is the recovery length. So, yeah, that can make a difference.


Chris Case  1:17:15

I think another point to bring up here in terms of effective HIT workouts is the fact that, in your opinion, consistency is key, and you don’t want to have a different workout scheduled every week, because then you don’t really matter, so to speak, that type of workout. Having the same workout from week to week helps you perfect that execution, which means the quality increases and you get more benefit from each workout.


Consistency is Key in HIT Workouts

Trevor Connor  1:17:50

So, pick a workout and stick with it. That is one of the biggest mistakes that I see athletes make where every time they’re getting on the bike, they’re doing something different. I also see coaches make that mistake where they feel they have to give their athletes these really sophisticated plans, and so every time they’re on the bike, they’re doing something different. My feeling is that leads to hitting every energy system, never really hitting any energy system hard enough, and can really plateau. So, when I work with my athletes, I always give them a primary workout, and we do it for the length of time that’s needed to really hit that system and get that super-compensation. Now that said, I still will have secondary workouts. So, the primary workout they’re going to be doing once or twice every single week, but I will give secondary workouts to either to hit a secondary energy system that’s not quite as important where you might just be trying to maintain it or frankly, sometimes it can get kind of dull always doing the same thing. So, sometimes you just need to throw in, let’s go do a sprint workout or let’s go do some over-unders keep it interesting, but the key thing here is you have that primary workout that for this block is what you are going to focus on hitting that energy system that you need to hit.


Chris Case  1:19:13

To step back for a second, there are these bigger buckets, in your opinion, in your mind of the types of work that you can do, but generally speaking, execution is more important than probably any aspect of it. So, let’s have you be more specific there. What do you mean by that?


Trevor Connor  1:19:34

Yeah, I know that’s really contradictory, and I know it’s a struggle to get that and I have certainly gotten emails asking me about that, going I don’t get it. If you’re saying 20/10s, 30/30s, does it matter? Aren’t I basically saying we’ll just go out and go hard, and it really doesn’t matter how? No, I’m not quite saying that though. As you know, I’m a big believer training races are fun, they are great you can get some good training out of them. But you’re still even if you’re picking from bigger buckets, you’re still trying to target energy systems, and that’s in the execution. If you don’t execute right, you might not get the results that you really want to see. So, let me give you an example. You know, I love my threshold Hill repeats. So, this is you pick an 8-to-10-minute climb, and you go and do it right around the threshold, and you do from four to six repeats. So, my prescription to athletes is, they all have to be the same length. So, if you do the first one at eight minutes, your longest one can’t be more than 8.15.


Chris Case  1:20:38

And by that you mean when you pick a start point, you pick an endpoint?


Trevor Connor  1:20:42



Chris Case  1:20:42

And you should really try to do that segment at eight minutes each time.


Trevor Connor  1:20:48

And the reason for that is we’re trying to train sustainability. I’m also really trying to hit that ability to produce power, mostly aerobically. So, really working on the anaerobic threshold, and the reason that consistency is really important, so to explain why the execution is so important, I see athletes who don’t execute very well taken an approach where they go out, hammer the first one, do an amazing time, do like 7.30, then they do the second one, they’re eight minutes, then they do the third one, they’re 8.30, and by the last one there at 10 minutes.


Chris Case  1:21:31

So, they’re not doing the same thing?


Executing HIT Intervals

Trevor Connor  1:21:33

They’re not doing the same thing. So, the reason they can hammer that first one is, all your anaerobic energy stores are completely depleted, you have all that to tap into. The aerobic system actually takes time to ramp up, so when you do these hill repeats, that first interval, even though it’s often your strongest, is the least effective, because you’re not fully using your aerobic system, you’re really using a lot of your anaerobic store. So, you go and hit it hard, not very effective, because you only sort of 90% hit the aerobic system. So, then the next time you do it, well, you don’t have as many anaerobic stores, you’ll restore some as you descend the climb, but not fully. So, you’re going to slow down because you’re still doing the same, I’m not fully hitting that aerobic system, and I’m tapping into what I have left of the anaerobic system. They just keep doing that with all the intervals. So, what you see is not a great job hitting the aerobic system, sort of hitting the anaerobic system, and then you have this workout that sort of hit every energy system but doesn’t produce a great adaptation in any of them. The reason all the lengths have to be the same, so they have to be consistent, again, that first one’s a throwaway, but each time you come back, you have fewer and less anaerobic stores to rely on, and you have to produce that power more and more aerobically. What you’ll find is by the time you get to the fourth and fifth interval, you feel like you’re killing yourself to do the same time, w the first interval if you did it right, you feel like you’re holding back. But by those last few intervals, you are producing that power almost entirely aerobically, and those are really valuable workouts because you are using all of your aerobic systems to try to hit that same time again. So, that’s why execution is important, which allows you to really hone in on the particular energy system. So, there’s a lot of ways to hit a particular energy system, and you can pick from those many different types, but you have to execute right to ensure you are hitting the energy system you want to hit.


Chris Case  1:23:35

Before we close out the episode, there’s one more thing we want to address, and that is, you know, we’ve talked about the particulars of intervals, but we haven’t necessarily spoken about how to fit that in or how to map that out in your weeks and your months and how to plan. So, we want to turn it over to Dr. Inigo San Millan, who has some thoughts from an episode we just recorded recently.


Dr. Inigo San Millan: Mapping Out Interval Training

Dr. Inigo San Millan  1:24:00

So, if you have, for example, two months away, I would divide into two blocks of training, to what is called the micro-cycles, and I like usually to do three weeks of training, and one-week recovery. This is wherein these three weeks of training, should still cultivate zone two, but yeah, you should do at least two or three times a week, solid high-intensity training, which I would tell that according to what type of race you are going to be doing in those two months, right? Is that a criterium? Or is it a short race or mountain race that is very long, with many climbs? So, this is where you should, you should tailor in my opinion, those high-intensity exercise sessions to the race that you’re going to do. I would say that two or three days a week is important, and you need to recover. The regeneration week, I would do that. But and of course, yeah, the tapering has to happen, right? Five days or so before your goal, right? Where you can do some activation sessions to activate the muscles in those energy systems, but at the same time you don’t want to train hard until the very last day, I’d like to get to know them, and see, you know, like, for example, there are athletes that are explosive and do very well in short climbs, but they don’t do very well in longer climbs, and to me that’s like, if you do well, in short claims, you should be able to do well in long lives. That’s my humble opinion. So, that’s what we try to work more on the weak points, right? We have identified, and we try to do more high-intensity during long periods of time, or sometimes the opposite, you know, some athletes are very good at 20-minute climbs, but not very good at a five-minute climb, and they go at seven, seven-and-a-half watts per kilogram, so you need to train that. So, that’s where you adjust things. Ideally, you have to improve in everything. Even if you’re Tadej Pogačar, you cannot be sleeping the low ones, right? You need to keep improving every year and keep stimulating those metabolic pathways and the bioenergetics, and regardless of the age, this is what we do. We see that so far in this last three years I’ve been working with Tadej, every year, he keeps improving a little bit, a little bit, and hopefully, he keeps going like that as well. But yeah, it’s about identifying the weak points and how we can address them in the most scientific way that we can, and this is where you need a very solid base before entering the cycling season. Once you have that solid base in the cycling season, yes, of course, you need to focus on two things. One thing is to improve that turbo, right? That high-intensity capacity, the glycolytic capacity. If you have a VC racing schedule, that is going to come pretty much on its own because the best way to get competition pace is the competition itself. If you don’t have a very busy schedule of races, and you only race 15 races a year, you’re going to have to train it, right? So, that’s the one thing once we get into competition. The other thing, the second bucket, once you get into the competition is the monitoring phase. So, we need to monitor athletes very well how they’re simulating training and competition because this is where overtraining starts happening. There’s not much overtraining during the offseason, but this is where in the during the season, this is where overtraining is very, very prevalent. I would not be able to tell you, obviously that percentage of people, right? But I would say that a good 60 to 80% of cyclists get overtrained during the season. So, it’s very important to monitor these to make sure that we rearrange both training schedule, maybe competition as well, and nutrition correctly according to the monitoring that we’re doing.


Chris Case  1:28:20

That was another episode of Fast Talk. Subscribe to Fast Talk wherever you prefer to find your favorite podcast and be sure to leave us a rating and a review. The thoughts and opinions expressed on Fast Talk are those of the individual. As always, we love your feedback, join the conversation at to discuss each and every episode. Become a member of Fast Talk Laboratories at to become a part of our education and coaching community. For Hannah Finchamp, Dr. Stephen Seiler, Kristin Armstrong, Grant Holicky, Sebastian Weber, Jim Miller, Dr. Inigo San Millan, and Coach Trevor Connor. I’m Chris Case. Thanks for listening.