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I'm not an exercise physiologist but I have an interest in it. The article states that more energy is used when the body is gearing up for an activity and I'm guessing this is because if you exercise for only up to a few minutes at a time with sufficient rest in between intervals then you'll end up mostly using the phosphocreatine and anaerobic glycolosis systems which are less efficient than aerobic glycolosis or aerobic lipoylsis. It's why when you start running without a sufficient warm up, you're always a bit out of breath even when running at sub maximal efforts and later on in the same run, even when running faster, your breathing can be super relaxed. The aerobic system takes a while to "spin up". In other words, you start with poor running economy... using more calories to run the same speed but as your aerobic system spins up, your running economy increases and you use less calories to run the same speed.

It's my understanding that by doing the type of exercise mentioned in the article - short bursts - you'll get positive physiological adaptations to your anearobic capacity but it won't have much impact on your aerobic capcity, which I would argue is the more important system to train for everyday operations of the human body!

This must be related to why HIIT is so effective at quickly dropping fat, even in short (<15 minute sessions). 10 Tabata sets of 40 sec sprints and 20 sec jogs has always been my go-to to lose some weight quickly, while continuing to run longer distances and lift weights.
Doesn't this hold for practically any kind of engine, whether biological or mechanical?
This is because maintaining inertia is efficient, despite the stress on the system. This is the reason High Intensity Interval Training and High Intensity Resistance Training work at all, because you're making a conscious effort in your exercise methodology to eliminate momentum and acceleration from the movements, which increases the work done within the context of your body, reducing the exerted energy lost to mechanical inefficiency of repeated movements.

You don't even need to stop moving while walking to see this effect in action. Just try walking so slow that you've eliminated almost all the momentum from the motion of walking. Just try it for a minute straight and see how it feels. (Forewarning: It's going to look ridiculous, like you're walking in slow motion.)

I hate shopping, because it’s start and stop all the time. I get tired after only 30m.

Then, I’ll walk home from the office (1h) and will have lots of energy to actually DO something.

The title resonated with me very strongly.

It can also be mental fatigue. Shopping is fundamentally making lots of decisions in sequence.
That's exactly why I find large stores like IKEA draining. My brain is constantly in decision mode, unlike even at work, where decisions are more spaced out. In stores, you literally have a conveyor belt of items passing through your decision system the entire time you're in the store.
I was walking through the narrow tourist traps that are the Venetian streets the other week. Lots of stores with shiny pins, bracelets, caps, hats and T-shirts. I realized then why I don't like stores: they're too cluttered. Doesn't even have to come down to decisions; just the visual impact makes me want to leave.

Perhaps this is what makes Apple stores work. Even webshops tend to have only a few products visible at a time.

My theory, after looking down the hallway of a mall and seeing a bunch of guys drooping on the benches and a bunch of women walking briskly, even joyously, is there is a coating on the floor that sucks the energy out of some of us and transfers it to others
Wow, your comment really hit it home for me. I have this exact same experience but never identified why I hate going to the shop so much.
The article doesn't say what is the best burst duration. From paper:

> Our findings show that the time-averaged oxygen uptake and metabolic cost are greater for shorter than longer bouts: 30-s bouts consume 20–60% more oxygen than steady-state extrapolations.

> After each bout, V̇O2 was measured during the recovery for 7 min while participants were sitting on the same chair

So, each participant (there was 10 participants) done a trial of bouts, each bout randomly 10-240s plus 7min rest.

Anything new here? Isn't it the same principle underlying Tabata/HIIT training methods?
I thought HIIT/Tabata was more about intensity so you COMPRESS a whole session in less time. This article is telling you that if you EXPAND the session to allow for pauses, you can get more out of it without increasing the intensity.
Thanks, I misintepreted it. So it's essentially about adding pauses every ~30 seconds.
Do I take this to mean that instead of running 5K at a relatively steady pace, I should instead break it up into several walk-short burst run-walk cycles?
Depends what you want to do. Run a fast 5k? Improve aerobic system? Something else? Short fast bursts of running will improve your anearobic capacity. Slightly longer intervals run a bit slower may target your lactate threshold and lactate clearance rates. Slower running for longer distances will target your aerobic system.

As people, and the featured article, notes, short intense intervals may burn the most calories but I would argue for more well rounded fitness you need to do a bit of everything.

Due to HIIT, there's loads of people around the world now who have great anearobic metabolism but non-existant aerobic metabolism. The effects are increased autonomic stress from all the anearobic work and an inability to exercise for long durations without quite a lot of stress on your body.

That... doesn't sound like HIIT. HIIT shouldn't average out to anaerobic heart rate ranges, otherwise you really lose the benefit of keeping your heart engaged in aerobic ranges during the rests. And to be honest, HIIT used for recreation shouldn't even peak in the elevated ranges above 167 bpm, if you're talking about doing it safely over years for health. Higher than that might be effective in training to increase aerobic capacity or lower your overall heart rate, but may damage your heart over time.

The effect of taking those controls on HIIT should result in reducing the autonomic stress response of /all/ exercise on heart rate, not increasing it. The demonstrated effect of HIIT is being able to efficiently scale aerobic capacity without increasing the time required and prolonged physical stress on the body. That's why Olympic athletes have been using interval training for a century, and from the 90s to this day, have used HIIT techniques like Tabata to increase their overall ability to exercise for a long duration, without having to actually commit to exercising for repeated long durations.

I'm not sure where you got that piece of information about loads of people with great anaerobic "metabolism" vs aerobic "metabolism". It would truly be very difficult, but not impossible to consistently raise your anaerobic capacity, (which I'm guessing is the implied relation to processing lactic acid efficiently as a fuel source for exercise?) but not raise your aerobic capacity also. Most of the ways I have seen that involve some kind of ketosis, or something that would otherwise deprive the body of the baseline glucose to drive aerobic capacity up in tandem with anaerobic capacity (because there's just not available excess glucose to store as glycogen in muscles beyond basal mechanical muscle operation and may lead to atrophy from burning muscle as a fuel source a.k.a. awful orange piss). And generally you would have a hard time building up extra muscle in that state as well, so it would be generally not advisable/possibly extremely dangerous to do so without proper diet and nutrition.

disclaimer - I am not an exercise physiologist or certified in any way. I'm an idiot on the internet, so please feel free to correct me if I'm wrong or don't have it quite right

My point is that if the capability of your aerobic system is very poor - and it is for the vast majority of people, including many HIIT advocates - then whatever exercise you do, you'll very quickly be approaching anearobic territory and find it very difficult to stay at a metabolic steady state for long durations of exercise. When I mean anaerobic, I don't mean "zone 5". I just mean that there will be a much higher percentage of anaerobic glycolysis happening than perhaps should be for a particular level of exertion.

For these people, their aerobic system is so bad that they need to walk to stay in "zone 2". It stands to reason that if they are doing a HIIT session then they are very quickly in the territory of zones 3 and 4, so we are looking at lactate threshold or critical power levels of exertion. So you are looking at more than 60-70% of power coming from anaerobic metabolism. That puts a lot of stress on the body.

For these people to develop their aerobic systems, they need to do a lot of slow jogging or fast walking. Eventually if they do that enough then they'll be much healthier, find HIIT sessions easier and recover much faster. People that spend too much time doing intense exercise will eventually end up with some degree of autonominc dysfunction. I've seen it plenty of times with HIIT people that want to start doing running. They train multiple times a week. Look stressed and knackered. Think they are aerobically fit but can't run a 5km in less than 20 minutes and can't run a 10km at all.

I do HIIT all the time, e.g. 20x400m on the track with 3min walking recovery. But as you noted, one doesn't do these sessions to increase ability to exercise for a long duration, you do long runs e.g. 25km at aerobic threshold for that. I don't do these sessions to primarily target adaptions to my aerobic system either. Instead, I do HIIT sessions like 20x400m with varying levels of recovery to target different apations. E.g. with long recovery I can target anearobic capacity. With shorter recoveries and a lower amount of reps, I can improve lactate buffering and usage.

Finally, it's reasonably well known in athletics circles that if you improve your lcatate threshold, i.e. increase the intensity that you are able to stay sustainably aerobic, then you end up decreasing your anaerobic capcity. The reason why is that the lactate threshold training reduces your ability to produce lactate.

Source: I've been running a long time and have coached runners of various levels.

Think they are aerobically fit but can't run a 5km in less than 20 minutes and can't run a 10km at all.

Is this a typo / did you mean 30 minutes? 5k in 20 minutes is already maybe top 2% of people who compete in races. And running a 10k is far, far easier than running a 5k sub 20.

Yes, sorry, you are right to point that out. I meant 30 mins!
So the data nerd in me is struggling with your framing a bit. HIIT for people with "aerobically poor systems" may resemble slow jogging or fast walking based on HR alone. Also outside of analyzing blood serum or glucose monitors, there isn't much of a reliable way to secondarily analyze the lactate threshold (actually). There are metabolite analysis that can be done, or things like creatine supplementation to facilitate the "smooth" transfer between aerobic and anaerobic processes, but on a fundamental level, my understanding as a lay person, is aerobic exercise produces lactic acid as a byproduct, and anaerobic exercise uses lactic acid as a fuel source. That is the reason anaerobic capacity decreases, as your lactate threshold increases. The real reason you are subject to a much greater degree of boom-bust is "lactate threshold training" is about increasing the physiological load the body is capable of sustained aerobic capacity for exercise (which is what you're saying), primarily by training your body to increase the amount of available glycogen. That's really only useful in the context of running and a few other endurance sports, and is hardly a metric of overall health.

Also IIRC the story of Marathon was relevant because the runner died to deliver the message. That sort of implies, despite the feat, that not everyone should be able to do that, nor should they.

HIIT conceptually depends on what your body does in a given state, not a unit of exercise. I would wager large sums of money the people that are overeager to engage with higher and higher intensities are not actually looking or reading the metrics of their own bodies, and adapting the behavior accordingly. It's not really about want or "determination" lol, it's about what you do to get your heart rate in a given place, and the fluctuations that produce an effect, given the systems in your body.

You kinda strawman these "HIIT people", as if they're actually doing HIIT, or as if they represent everyone. Autonomic dysfunction, based on overtraining syndrome or overexertion is not the same thing as observing a HIIT protocol based on your own biometrics. It's honestly hilarious, because HIIT and interval training at large is specifically designed to avoid OTS, especially where it relates to the serious damage that can occur to the vascular system, musculature, and ligaments, once scaling up the duration with a similar level of intensity occurs. Running a 5km in less than 20 minutes is a perfect example of a not very good metric actually. There are plenty of people that could put themselves at risk of damaging themselves to do such a jaunt. It is a very light entry point, but arguably is a good metric for elaborating on why training is important to be able to accomplish physical feats safely, but there's kind of a packaged Ableism in your argument that I kind of find distasteful. If your doctor looks at blood serum, analyze heart rates under stress loads, and examines blood oxygen under stress and during sleep, you can pretty much guarantee they will arrive at some degree of analysis that could prove (outside exception of health conditions or illness) a degree of general health and fitness.

I understand running is important to you, personally and culturally. Don't attack tools in the toolbox of fitness, just because you see other people using them wrong (edit: you did say you do use it). Everything in the world is a nail if you're holding a hammer, etc etc.

Conceptually, most of what you said is sound, but yeah. I think you're a nerd for process, which is cool, making kind of misguided arguments that are not really about what we're talking about here, which is why the article observes a principle experimentally we've known works for over a century. Also I personally like HIIT, interval training, and HIRT especially for all of the reasons I've described. :)

It depends what your goals are. But if you want to burn calories, intense intervals are known to be a much more efficient approach, yes.
Only if you want to burn more energy. If you're going for shortest time, you want the steady pace.
Yeah, that's a known training method, "High-Intensity Interval Training", HIIT.
Interval Training

Makes sense ... short walking bursts is a mild form of 'interval training', which has been shown to have major benefits over constant/prolong exercise.

Two questions: had these bursts same W(=FS) over time or proportionally less due to stops? Iow, slow-fast vs normal or slow-normal vs normal?

Did they measure energy consumption for replacing short-term resources like creatine phosphate, glucose, etc? Instant oxygen consumption probably doesn’t paint the whole picture. Blood tests obviously required?

May it also be explainable by the additionally needed acceleration of the body mass?
> To find out, they recruited 10 volunteers.

I mean, It doesn't look like such a complicated study, no? Why didn't they check, IDK, with at least 100 people? With 10, which is 5 per sex, it's almost impossible to not just be anectdata.

Cue John Cleese
If silly walks were efficient we wouldn't view them as silly.
you ever tried to replicate his walk? Its anything BUT efficient or easy.
Can someone please tell the Fremen?