Aerobic Metabolism, LT1, and the Inefficient Athlete


So I was quite impressed recently by a talk between Peter Attia and Inigo San Millan. In the video they essentially made a strong argument for time in Zone 2 training defined by an athletes individual LT1 levels being the Zone 2 upper limit. Inigo looked at elite athletes and made some profound statements relating to elite athletes having more mitochondria density which in turn gives them the ability to use lactate as a fuel source better than the average person. Their LT1 occurs at unfathomable levels such as 300 watts+.

They made a number number of statements on mitochondrial function and how it could be involved in numerous physiological limiting factors in endurance athletes. With that being said, I follow Trainerroad, Fastcatcoaching, and a ton of the principles of Dr. Andy Coggan and other sweet spot advocates. All of those individuals push for sweet spot being a large portion of an athletes training for preparing for racing. I would say I follow more of a pyramidal style training myself that is inspired and rooted in the theory of sweet spot training.

Diving deep into the weeds of the physiology, Dr. Any Coggan and his chart that lists the benefits of sweet spot physiologically (the one with the x’s) seams to make a case that “comfortably hard” training incurs a lot of bang for the buck. What I struggle with, however, is the opposing view points presented by speakers such as Dr. Inigo and Peter Attia. This essentially boils down to the polarized vs. sweet spot debate but I like how Dr. Inigo at least backs his philosophies up with measurable, meaning in the lab, information. I get the impression Dr. Coggans research, among others, is more macro based. Meaning, he looks at how people train and they get this result etc. I get the impression that Dr. Coggan and other sweet spot rooted physiologists understand how their training ideologies get athletes faster, but, I feel like the explanations I have found are more nuanced when it comes to the raw biochemistry and physiology. I get the impression sweet spot works at getting people faster, I am one of those athletes as well, but I want to know the overall picture more. Maybe this is just a gap in my knowledge and someone can point me towards lectures or talks that give a more detailed explanation of the biochemistry. Does anyone have any information on studies that looked at mitochondrial function in sweet spot vs. polarized trained athletes? I hate to think training with a lot of sweet spot is literally destroying my mitochondrial optimization.

In conclusion, I wanted to get the communities thoughts and statements on this topic. One that is probably debated about endlessly on this form from what I can tell. Does anyone feel that sweet spot makes them faster, but is getting them faster in a unhealthy physiologic way? For myself, I wonder now if I am taking the entirely wrong approach at building my base. I am building a base according to Dr. Inigo that is built on mega burning carbohydrates and inefficient production and tolerance for lactate. According to his philosophy, if I followed a more polarized approach I would build more mitochondria, more efficient mitochondria function, and increase my ability to utilize lactate as a fuel source within my mitochondria as a result. Anyone have any thoughts on this profound statement? Because that one thing seams to be a huge blow to the entire foundation in which Trainerroad (and my current training in Sweet Spot Base I) is build upon!

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See Episode 326 of That Triathlon Show. :grinning:

I don’t think it’s an opposing view. Attia is interested into health and longevity. San Millan’s coaching has won the Tour de France. Also, San Millan is not Z2 all the time or polarized. He’s probably pyramidal with a wide base when all is said and done.

If TR’s customer is at SSBLVI, and only wants to do 3 rides per week, 4 hours per week, then there are limited options to make them faster. The levers of exercise are volume, frequency and intensity. A low hour athlete is limited in volume and frequency which only leaves intensity.

Now if you have all the time in the world (like Pros) you can build a lot of capilliaries and mitochondria with lots of muscle contractions (volume). The lower the intensity the more muscle contractions one can do day after day. Even pros can’t do 3 hours per day of sweet spot.

Pros also have frequency on their side. They can train 5-6-7 days per week and even 2-3 times a day if they want.

Don’t think of all this as “either or”. The answer is all of the above and a good coach knows how to mix every training stimulus for maximum total effect. Exercise physiologists try to isolate one modality to study it.

I recommend Phil Skiba’s new book. He lays out pretty plainly why you want to train at Z2, at threshold, or above threshold. (BTW, sweet spot is basically threshold training.)

On this podcast he talks about polarized training and periodization.


I found this guest very disappointing. His knowledge was mostly derivative and his recall of it was subpar relative to the host.

We have been discussing this topic (a good one) for a few years now. See above.

One thing I can’t wait for Trainerroad to incorporate, is outside training that isn’t biking. I realize it would be difficult for TSS to be calculated from my trail running (which is done at Zone 2, I use running power) but this is how I drive my training to be more pyramidal. Right now I rely on subjective feel and I use Garmin’s training load system and HRV to know if I am overreaching. I am all for adding Zone 2 on the bike along with low volume sweet spot Trainerroad plans, but, I just can’t sit on the saddle for more than an hour and a half before being in pain. I probably need a proper bike fit, but, I honestly enjoy trail running as a Zone 2 modality better anyways.

Fantastic thanks for that, will certainly be taking a look at that thread.

You could try using one of TRs Polarised training plans for a few months, but if you don’t enjoy that kind of training ,is there much point in doing so? And will it be the difference between a podium finish, or a lower placing.
And how will you know if it is related to your training ,or some other reason.
My thoughts on this are, be open to trying new things, but do what you enjoy ,and what works for you.

I’m now going to listen to the podcast shown in previous post!


To answer your question, based on a lot of input and experimentation, I have had great success with endurance + tempo (not quite strict LT1 training but just slightly harder…76-.81 IF…sometimes .83).

I’ve actually just set this up last night to give it a try. Mostly because I want to work on a couple local KOM’s and feel its time to switch over to Zone 5 and above energy system training along with Zone 2. I have not really done any Zone 2 training on the bike (other than trail running on the weekends) or Zone 5. It’s been all Threshold following the Sweet Spot Base. I am interested to see how I perform on these short KOM’s having a Threshold built base. I will give it a go and see how I feel, last year I attempted to train at Zone 2 using just heart rate and managed to build up to 8 hours a week of Zone 2 on the bike last July, there was no Zone 5 at all back then and I can’t say I broke any FTP records. When I retested on a 20 minute test I had very very small improvements. I really gave Zone 2 training my full time an attention back then with no Zone 5. Will see how this time goes adding in Zone 5 along the way and not removing it completely like I did that 4 week block.

One system trains the metabolism, whist the other trains the aerobic (not mutually exclusive, of course)… use both… at the right time!

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Ok, couple of comments on this. Zone 2 and threshold/SST should not be “either or”. Even within a SweetSpot plan (be it TR based or of your own design), you should have generous amounts of Zone 2 riding (~.65 IF w/ no big swings in VI). There are no strict percentages, despite what the internet says.

Reading what you wrote above suggests to me that you are thinking “Zone 2” and “Zone 5” and “SweetSpot” are mutually exclusive. You have to find a way to blend them all that works for you.

Also, avoid the sweet spot vs. polarized debate ← I just saved you a few years of confusion and/or time waste. You’re welcome. :smiley:

YOU ARE ASKING GREAT QUESTIONS! But there is not a simple “go here” to get a definitive answer. All that stuff you learned from Inigo San Millan interview and mitochondria, etc. All valid. But riding in one training zone isn’t going to give you that. Unfortunately it’s not that simple.

Most of what you commented on regarding Andy Coggan is not correct, but it’s not that important for what you’re trying to do.

If I were you I would get an online coach. When you’ve spent a fair bit of time in the TR bubble it can lead to polarized thinking, over-simplification, and a lack of understanding about how and why you’re doing what you’re doing. The podcast, blog, and forum certainly help, but it’s a big time investment. If that’s fun for you, by all means, do it. You’ll be spending a few years closing your knowledge gap. Alternatively, you could short-cut the process a bit and hire someone for about a year. Many ppl on here have a coach AND use TR platform. Nothing wrong with that.


Thanks for the information! I come from an exercise physiology background that is very reductionist in thinking (I blame academia for that). When I got to the end of grad school, what I appreciated the most is how one mentor of mine broke me out of the reductionist mindset of thinking and into more of a holistic way of thinking. I feel like my masters program focused extensively on the “how” the body works part but failed to really offer up any foundational ideologies for training. In the end, I think that was the point though. As I have moved on from my schooling to applying this in the real world I am realizing their is ALOT of ways to approach this. Entire companies are built on different schools of thought including Trainerroad. Nonetheless, I am glad to have found this community because we can get into some real deep deep discussions. Great stuff! I think one of the hopes of signing up for Trainerroad as well was their structured workouts. Can’t say we ever properly designed intervals, periodized plans, or macro or mesocycles in my grad program. Perhaps if I chose more of a strength and condition track that would of been more inclusive of that. I do agree that a coach (or even just using Trainerroad as a platform) is going to help me fill in the coaching gaps. Application of knowledge to the real world is both part art and science. It if funny to see the different camps we get into.

Starting TR SSB after an off-season I always gained ftp. However above about 5-6 hours/week I gained even more ftp and ‘a deeper aerobic base’ by doing more zone2 and fewer intervals. That would NOT be true for everyone, some would respond better to more intensity. Some might only see more gains by doing more zone2 above 8-10 hours/week. We can discuss/debate/speculate about why different athletes need different approaches, but I think that misses the key point.

The key point is you either figure out what’s right for you by trial and error, go get tested to help determine the right approach, work with a coach, or simply use an off-the-shelf plan

Off-the-shelf plans from other coaching companies and TrainerRoad do not start with a full assessment of fitness and the target event, and then design a custom training plan. Pragmatically they do some level of assessment, make some assumptions, and use that to build plans designed to have you peak for an event. In the process you will develop good fitness for the event.

What if you had 5 hours/week to train, and an ftp at 75-80% of aerobic capacity? You have limited time and a lot of room to push up ftp as % of aerobic capacity… if that was me (it isn’t) I would probably do more sweet spot like SSB1 and SSB2. On the other hand what if your ftp was 85-90% of aerobic capacity? I think it would lead to a different answer on what to do with 5 hours/week. Going back to my earlier point, I found thru trial & error that more zone2 led to bigger gains during base and beyond, somewhere above 5-6 hours/week (I’m the ‘off the couch’ ftp is 85-90% of aerobic capacity type).

Ultimately you need to be engaged as either the head coach, or think of yourself as an assistant coach and seek out help.


All fantastic points. I feel the same way, above 5-6 hours a week I can’t break through barriers without having the training be Zone 2 training. The low volume sweet spot base for my own physiology seams to be at the edge of my recovery ability. As a weekend warrior, I use trail running at low intensities to supplement Zone 2 time on the bike. I guess I will see if it translates into more success on the bike. Trial and error always, I think realizing how many different philosophies out there there are for optimizing physiology I have been able to adapt training more to an individual level (what all good coaches should do in the end). Hardest part is finding the personalized Zones of an athlete including myself, but I see some of the other threads you are on expresses that same question as me. Good stuff thanks!

Why? To get good a cycling ride your bike. To get good at running, run. Running doesn’t make you good at cycling. Specificity of exercise. What does supplement mean? Are you a triathlete? Don’t get me wrong, run if you like it. But don’t tell yourself it will improve or “supplement” your cycling fitness. It won’t. Great for general health. And if that’s why you’re doing it, that’s good. But it isn’t cycling. Different muscle groups. Specificity.

So since you have a background in ex phyz, let’s have some fun. Where is the mitochondrial biogenesis occurring (generally) when you’re running. Where is the mitochondrial biogenesis happening when you’re cycling? There are other adaptations of course, but let’s start with those since you mentioned it earlier.

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I have really struggled with pain on the bike for extended periods of time. You are correct in that it is a total assumption that running will translate over into better cycling performance, but, I have a hunch the physiology will work out that way. Perhaps I need to dive into the literature to see if there is any clear cut data that confirms this occurs. While the overall specific adaptations to training definitely do not transfer over in a linear way, I believe the general stressors that foster adaptations both cardiac and metabolic will benefit from trail running and transfer over to on the bike. I feel the metabolic adaptations are going to be more translatable for me, because of the general fact that I will be staying below LT1 nearly the entire time of trail running. RPE is my foundation for knowing if I am below LT1, but I play it on the safe side and generally would describe my trail running as run walk trail running rather than a continuous effort. Volumes are in the area of 3 hours or more out on the trails. I would hope all that low intensity work would foster some metabolic benefits!

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Just coming back to your original post, for sweet spot base I’ve done TR MV/HV, and FasCat Intermediate and CTS Intermediate, and the FasCat/CTS have fewer intervals and more endurance. The FC/CTS approach is roughly 60-80% endurance work, on a budget of 8+ hours/week.

TR high volume plans are roughly the same hours/week as off-the-shelf Intermediate plans from coaching companies, but considerably more intervals. It really is a different approach, I’m older and need more recovery but am doing “high volume” by TR definition Is a High-Volume Training Plan Right For You? Five Questions to Ask Yourself. - TrainerRoad Blog and that article is giving volume advice that is VERY specific to TR high volume plans. Compare the number of intervals in the short power build example in that article to the criterium build approach my coach wrote about here: Criterium Training – FasCat Coaching where the goal is to do fewer intervals and still be well prepared for the event.

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Since the theme here touches on sweet spot, recovery, and older athletes, I have a related question since I have been doing a tempo/sweet spot plan.

How much fatigue, soreness in the legs do you all carry workout to workout? There have been periods where I wake up almost every morning with a little soreness in the legs.

I over cooked it a bit in Jan/Feb when I did 6 weeks straight. I was just feeling great after 3 or 4 weeks and I took a few extra rest days here and there so I kept going and then the fatigue hit me like a ton of bricks.

My new strategy is to take a mandatory easy week after three weeks on whether I feel like it or not.

I’m also trying to insert two easy days between hard workouts. Instead of three hard workouts per week, it works out to more like 5 workouts over 2 weeks.

Any thoughts?

For me its less about the legs and more about the sleep/rest. When you start waking up tired and can tell you have had a restless night of sleep that is when it gets to be too much. I can ride through sore legs for awhile before I need a break as long as the sleep is okay, and I already sleep less than needed. During heavy training weeks I’ll be using a massage gun almost every night and rolling but can keep riding for weeks on end with only a few rest days a week, almost never taking time off the bike as I bike commute year round. I’m not old(38), but older than when I was just getting into the sport so I’ve learned my lesson a few times with overtraining.