From the Coaches: Long slow duration and why it still has its place in your weekly training

Training From The Coaches
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I think anyone who claims to understand all this doesn’t:

Tons of great variables discussed there, but one thing I distinctly notice is a lack of any mention of low intensity work building mitochondria better than high intensity work. At best they say high volume builds well (uncontraversial), but that it’s even possible that high intensity work builds more per hour. I’ve read the same with regard to fat burning. Yes, you burn a higher glucose percentage at high intensity, but are you actually burning fat slower in absolute terms? Not from things I’ve read. (Edit: I can still find this written from professional sources, but actually it seems clearly wrong from published data)

So it seems to me still an outstanding question: Does low intensity exercise really do something high intensity doesn’t? Or is it just about putting in hours on the bike, and what you can handle regarding hours in the high intensity side and needed recovery from it? If the latter a one-size fits all ratio (80/20) might not make a lot of sense, particularly for veterans with a lot of forced recovery time maybe?

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Define low intensity.

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Obviously there is no one clear definition, and that’s where a lot of the discussion is, even in the Millan interview, but everyone seems to define this as something at least 20 or 30 bpm below 1-hour pace and conversational talking. The article I linked also pointed out the question, but their definition didn’t seem far off from that. Millan seemed to think it’s not SO easy to spoil his claimed low intensity effect and he wasn’t afraid to push it a bit. The question to me isn’t to define low intensity, but to define what if anything, other than the obvious recovery time, mental drive, and ability to do more hours(if you have them), is actually lost at high intensity? I don’t see any truly compelling answers to that at all. Here is another interesting article:

One notable variable there is the proportion of slow twitch to fast twitch mitochondria. It still doesn’t say that HIIT generates less slow twitch mitochondria per hour than “MICT” but it’s a question.

Edit: Basically, I’m asking, do (let’s say already fit) people with limited time really need to bore themselves going slow, or is it enough to apply common sense to not burn yourself out? I’m not so sure the argument for the first is clear.

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I would doubt any scientist would define low intensity in terms of an absolute number. 20-30 bpm would not be so large for a 20 year old rider, for somebody older such as myself it would be a huge number. Conversational pace, which Millán agrees with, is a much better sign.

What is lost at high intensity is a focus on the fat burning system. I am sure Millán is well aware of the relevant literature. Zone 2, at least for a lot of us, is not an easy or slow effort. Millán states that the lactic generated by high intensity efforts is used by cells in preference to glycogen. It certainly, would then be used in preference to the breakdown of fat. Hence, that system is not trained.

As for what you have to train, it depends on your goals

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Stephen Seiler has stated simply in one of his Youtube video’s “How low can you go” I think it is, that the lower you go in Zone two intensity (HR) the longer the ride would need to be to get the same benefit as riding at the top end on the zone for a shorter time.

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If there is any definition anywhere near this ballpark for which my questions have clear answers that would be fine with me, and there may be. Zooming in on the exact definition is less interesting and surely impacted by personal variation.

This is interesting, although sponsored:
https://www.gssiweb.org/en/sports-science-exchange/Article/nutritional-factors-that-affect-fat-oxidation-rates-during-exercise

Indeed they do show absolute rate of fat burning decreasing with intensity, contrary to what I said I’d read before.

But they do say:

However, it should be highlighted that increasing fat oxidation during exercise is not associated with improvements in performance. Therefore, methods to increase fat metabolism should be incorporated into training programs at specific times of the athlete’s season, not associated with competitions.

At some level of course that’s not controversial. The question is maybe at what level, and how does this all reconcile with the mitochondria building from the my first link? Van der Poel seemed to take it quite literally.

Another interesting thing Millan said was recovery to zone 2 could take anywhere from 5 to 30 minutes depending on lactate handling ability, a big window, and what training impacts that?

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I would image the 5-20 minute range depends on your ability to process the byproducts of the glycogen process (lactate, hydrogen ions, etc… That is the one of the ideas behind all those intervals with minimal recovery we love to do in Sufferfest videos.

As for fat burning not improving performance, I am not sure what that means exactly.

The ability to ride for longer and longer periods is a form of performance improvement. You are not riding for hours on glycogen Even in a race, your ability to ride in lower zones enables you to minimize the time for the final sprint. Often, a rider’s final sprint may fail not because they are poor sprinters, but their “aerobic” engine was not strong enough to get them close enough to the finish line.

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Of course you burn fat on long rides, if you try to or not. But does burning the most fat, in limited hours, actually do the most to improve the amount of fat you can burn? Is maximum fat burning even limited by anything specific to fat burning itself, as oposed to just availability of oxygen and the Krebs cycle (also used for glucose) in general?

Looking through some literature, a couple of things hit me. HIIT, may improve fat oxidation as much as, or more than, riding slow for the same hours, again ignoring fatigue/recovery concerns that may limit useful hours. This is interesting since MAP efforts use no fat at all, but both improve mitochondrial function and Krebs cycle availability. But then it seems we don’t even really know why or fully how fat burning gets actually shut down at VO2max. Probably it’s for the obvious reason that it uses about 10% more O2 per ATP than glucose, and maybe more blood flow too. So the “best” you can hope for is to burn 100% fat up to a power level of 90% VO2max glucose power and then instantly transition into glucose as needed between 90 to 100%. But really we need to switch over starting earlier, and more slowly so we get a lot more power already at 75% to 85% of VO2max where we can actually sustain it, and that’s what happens. Is it even clear that there is any optimization to be possibly gained in tuning the crossover curve, and if so what are you optimizing for? Do highly trained atheletes have a FATMAX at a higher percentage of VO2max? That seems unproven at best. Increasing that would increase fuel reserves at 85% of VO2max, but would reduce power there. (Edit: this is even more complicated because FATMAX isn’t fixed. It seems it already re-optimizes as we deplete glucose)

Then will zone 2 work increase VO2max? Can “improving” fat burning increase VO2max? Or does VO2max increase ability to burn everything, including fat? The HIIT evidence says the latter is true.

Long rides, will use fat for sure. You don’t have to force that. You can’t avoid it. Yes, riding at “FATMAX” will use a bit more, especially in shorter sessions, but that doesn’t prove much else.

I’m a huge believer in science, but also in the human body’s ability to adapt to what you ask it to do. If you ride mostly to kill the weekends, then trying not to kill the weekends may be a poor strategy. If you’re training for some longer event on <10 hours a week, the answers are less clear. I think you need long rides to train long rides. Do slow short rides also help? More than fast short rides? Enh… maybe?

Are lots of winter base hours good? Probably. Is 80/20 reasonable? Rue the Day, itself a HIIT workout is 60/40, so sure, by time it might be.

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From the OP.

“Due to the continuous nature of this signalling pathway, long duration exercise is more beneficial than shorter in this respect. The only way to conduct this exercise sustainably is to perform it at lower intensities.”

Yes, long rides require some reduced intensity. But that’s a different statement than the argument that one should make an actual point of reducing intensity in limited hours.

“Additionally, studies have found that, as intensity increases, VEGF activation decreases and angiogenesis is hampered, which is why low-intensity exercise is so important for angiogenesis. These benefits are theorised to occur more in the long duration exercise due to, again, the continued muscle contractions over far longer time durations than for, say, 60 minutes of high-intensity training.”

This part is certainly very interesting. Are 1 hour low intensity sessions helpful for this in particular? On long rides how much benefit is achieved necessarily by way of it being a long ride and how much more is gained by actually make a point of holding back the whole ride?

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100% this. No point in discussing performance without any defining framework within which to perform.

If shorter TT’s and CX is what you aim for, I guess you have less use for long low-intensity rides (although you probably benefit if you happen to have too much time on your hands). However, if longer road races are your cup of tea, then it seems clear to me that you will certainly have use for this, as durability becomes more important.

Recently read an interesting article on this, summarizing several recent studies looking into this. Particularly interesting I found the part pointing to low intensity by the start of the ride may be moderate intensity e.g. 2 hours into the ride.

This summer I am doing a 430 km (4600 m climb) sportive, and I am definitively not gonna be able to do it relying purely on intervals.

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I’ve searched the thread for this, but it’s big, so I may have missed it. My question is, if I have several big years with lots of low-intensity 5-6, even 8-hour rides, will the mitochondria built in those years still be present after a couple of years with less mileage and few rides over 4 hours?

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Also, Fast Talk podcast had an episode discussing the benefits (if any?) of a one hour low intensity ride which could be worth listening to for those interested.

Is it beneficial? It depends. As it aaaalways does :wink:

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Also wondering: if you do several 2h zone 2 rides per week, outdoors, and the weather becomes bad, is it useful to do some zone 2 work indoors for 1 hour (no way I’ll be riding that KICKR for 2 hours …) or is the shorter stimulus useless as your body is used to longer riding now?

btw about that 80/20 rule. I think irrespective of what works best for endurance training, if you spend too much time blasting high intensity workouts you will probably dig yourself in a hole, and I don’t think it’s really healthy to push your heart to it’s limits every day of the week, especially as we age.

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The 80/20 rule is often not understood and results in doing too much HiiT. I really rate Stephen Seiler and to spend 20% of your workouts in such a high intensity is wrong. He states that we should be thinking of “time” at high intensity which is more like 10% of your training “time” (so 90/10) is more the correct figure and not 20% of your workout time. There is a big difference.

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1hr of Z2 is better than zero hours.

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I’ve changed my approach too, compared to one year ago where I did 3 HIIT sessions per week indoors.
I do 2 high intensity sessions per week max. I’m 44 and I ride XC MTB. That means either 2 indoor trainings, or 1 indoor and 1 XC ride outside, or 2 XC rides outside, in 1 week. Where I live the XC rides require me to max out plenty of times because of steep/technical climbs.

If I want to ride more it’s either Z2 rides or I will take the (am I allowed to say it on this forum?) enduro eMTB I just bought if I already did much riding that week, which equates to Z1 riding (but I can have fun riding downhill without adding too much fatigue in the legs).

On top of that I go to the gym 4 times a week, 2 upper and 2 lower body days. Adding more HIIT to this schedule will have me digging a hole I can’t get out I’m afraid.

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Also, what defines “time in high intensity”. If I do a 1h workout (let’s say 14 Vice Grips), you’re not riding for 1h at high intensity (if you could, it wouldn’t be high intensity), but you are riding 16 minutes at high intensity. The rest is recovery. For a 1h workout.

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Note also the important boredom threshold for z2. Mine is 0hrs of z2.

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Outside it’s ok. It’s a good motivator to transport the bike to a new area and just ride around enjoying the environment.
Indoors, yeah … it sucks. Unless you want to binge Netflix or something else, because the effort leaves your brain free to process video and audio, which is not always possible when tackling intervals.

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Honestly, even outside I struggle.

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