This shouldn't come as a surprise; "mental" and "physical" aren't distinct entities, our bodies function as a whole. Having to state this is, I think, a reflex of an ever-present dualist view of the body (in the Cartesian sense, i.e., mind vs. matter).
As a rock climber, I can tell you that mental and physical fatigue are very distinct, very real things. But I'd have to say that before I got into climbing, I wouldn't have realized this.
There are times when you are physically capable of completing a climb, but your mental tiredness prohibits you from doing so. The very nature of climbing is scary, and your brain knows this. It's not just fear of heights, but fear of falling, and even failing. Every move you make is a little fatigue on your mind. You have to calculate it out, make the move, and beat all your fears at the same time.
Over the course of a climbing session, your mind wears down. You may be physically able to complete a climb, but your mind is just giving up. The stress overwhelms you. You give up.
There is another non-rock-climbing example. In Arnold's bodybuilding book, he talks about the mental aspect of bodybuilding. Not just in competition, but also in training. He gave an example of some famous bodybuilder who was having a bad day. He couldn't do some deadlifts (I think) that he was totally capable of doing, even with Arnie cheering him on. The guy was about to give up. Then a bunch of his fans showed up, and he wasn't about to disappoint them. He completed his set with ease.
you're right, weight training is 80% mental. on any given day, the work isn't that hard. cumulatively it's just a few minutes of effort and you've done it a hundred times before. you know when you finish you'll feel amazing, and you know in 1 month you'll have more solid results compared to today. you know all this.
but damn, sometimes you just want to quit for no reason at all. i've come so close to just walking out in the middle of my workout for absolutely no reason whatsoever. this is even after you've gone to the actual gym, which is a whole 'nother story.
Why is this kind of comment (a la "no duh, scientists!") always highly praised on the Internet and in general, even from otherwise intelligent, thinking folks??
Since when have we been okay with "no duh" being our source of information? Come on guys, we have to figure shit out before we get to say "no duh", and then instead of saying "no duh" (which is another word for "common sense", which we all laugh heartily about in other contexts) we get to cite the studies and the research that provides a strong correlation.
I was a scientist until a few months ago (until I finished my PhD, essentially), so - believe me - I know the value of studies which "state the obvious", even when the conclusion seems "small" (which isn't the case, anyway).
My previous comment wasn't meant as a "no, duh", really. I'm sorry it came out that way. I'm highly favourable to studies which prove "common sense" (or disprove: those I live even better!). The comment was just to share my opinion: the fact that this kind of studied is shared (here, and in other media) highlights how dualism is still basically the common sense view.
For whatever it's worth, I didn't read their post that way. Unsurprising results, validating a null hypothesis, that sort of thing, they're all valuable, but this particular poster seemed to be using the opportunity to bring up their distaste for Cartesian duality and its over-appreciation by society at large. In a sense, "this shouldn't come as a surprise, but it's good they did the study since it stands as another data point in refutation of what's become standard folk dogma about mind/matter duality" -- or something like that.
In any sense, their sentiment didn't seem to be at all opposed to yours, at least to my reading.
> This shouldn't come as a surprise; "mental" and "physical" aren't distinct entities ...
In one critical sense, the mind and body are distinct. The body can be scientifically investigated because it yields objective, empirical evidence. For the mind, you have to ask the mind's owner what he's experiencing, and that leads to all sort of well-documented distortions.
>For the mind, you have to ask the mind's owner what he's experiencing
This isn't really a legit distinction. Describing "the mind" as separate from the body because we don't know how it works is like describing cancer or AIDS as separate from the body because we don't know precisely how they work. All of cancer, HIV, and thought stem from biological processes that we don't fully understand. That doesn't mean they are somehow not the body, it just means we don't understand the body.
> This isn't really a legit distinction. Describing "the mind" as separate from the body because we don't know how it works is like describing cancer or AIDS as separate from the body because we don't know precisely how they work.
From a scientific standpoint, yes, it's legitimate. We can gather unambiguous empirical data about the brain and the body, the meaning of which different observers will accept, but we cannot do that for the mind.
> All of cancer, HIV, and thought stem from biological processes that we don't fully understand.
Yes, but we can diagnose the first two objectively, so they're much more objective and scientific than what people choose to report about their minds. A microscope image of a pathogen has it all over someone's verbal report that he's sick.
Consider this example -- a trained actor can simulate all the symptoms of Alzheimer's, such that a psychologist will provide the diagnosis (as they regularly do), but that same actor will not get the diagnosis from a neuroscientist using an MRI scanner, because the latter method can produce an objective diagnosis that the former cannot.
> That doesn't mean they are somehow not the body, it just means we don't understand the body.
It's all relative. We may not fully understand the body, but we understand it much better than the mind. This is why psychologists have had to abandon promising diagnoses repeatedly over the decades -- such diagnoses often create a huge public uproar, then they're discredited, then they're abandoned. Psychologists can make a popular diagnosis like Asperger's disappear by removing it from their diagnostic manual (as they recently did), but that doesn't work for cancer and heart disease, because the latter conditions are real.
>From a scientific standpoint, yes, it's legitimate
No, sorry, it isn't. You can't gather empirical data about 'the mind' because it is a category you made up to describe a set of symptoms but which you are confusing for an entity.
> You can't gather empirical data about 'the mind' because it is a category you made up to describe a set of symptoms but which you are confusing for an entity.
No, I'm not doing that, psychologists are. And psychologists insist that the mind is a suitable topic for scientific investigation. You've managed to confuse me with a group that I spend much of my time criticizing for their scientific pretensions.
I'd say no, but I'm a layman. I think the situation you describe is "just" an interaction between different systems which, together, make the whole open macrosystem which is your body. If I can push myself to go even further, I'm probably triggering something in my nervous system (via a high-level cognitive process - motivating myself, thinking "positive") which will in turn signal other systems which can then provide energy or stimulation to go on.
Some feedback loops between the brain and the rest of the body are more mysterious to me than others. F.e. the placebo effect is something I find hard to rationalize in many cases.
This particular connection really seems kind of obvious. My amateurish explanation would be that every voluntary muscle movement has to be actuated by brain activity, and hard workouts require a lot of muscle steering. If the brain is tired (which means its stores of energy or some other chemicals/transmitters are lowered/exhausted) it becomes harder for it to induce muscle activity.
This also works the other way around. For example, when doing heavy weightlifting in the gym, the central nervous system takes a huge blow, and most people will certainly feel some mental fatigue the hours and possibly even the days after a workout session.
From a personal experience: my best days are when I get a good morning workout in. I feel energized the rest of the day. I think the sense of early accomplishment helps in a way.
There's workout, and then there's workout. Try squatting 405lbs or deadlifting 495lbs for reps (or whatever your limits are when it comes to maximum exertion). That stuff wears you out pretty good. I wouldn't recommend doing it in the morning. Cardio, light lifting, sure, but that doesn't really tax the CNS that much.
What constitutes heavy lifting in this case? I find that in a regular gym workout, if I'm doing some sort of circuits with moderate weights, I'll fatigue physically by the third or fourth circuit as you would expect. However, if anything I tend to feel more alert and mentally capable after a workout, at least by the time I've got home, showered and changed.
Anecdotal: I experienced this doing stronglifts 5x5, which is a program that systematically keeps you lifting near your 5 rep max. Squats in particular seem to mess up my CNS. Moderate weight lifting is awesome for my mood and cognition, heavy weightlifting is destabilizing.
Did you end up changing your routine or did you stick to it? I started stronglifts 5x5 a few months ago and the weights are heavy enough now that I'm failing sets in most exercises each session. It's hard to get the motivation to keep going.
As an amateur weightlifter and professional programmer, I've definitely noticed reduced performance following a hard release cycle.
What's interesting is that I usually hit PRs immediately after a mental fatigue, but a week or so afterwards it catches up with me and my performance in the wightlifting hall goes down.
I also lift. You're not going to be able to maintain the peak required for PRs week over week. Don't even try. Take the gains as they come, focus on your training, diet and sleep.
If you feel like you're not improving, change something.
Weightlifting is mostly mental discipline, acquired via training. A very large percentage of the increased weight you can move is due to improved form and increased recruitment of the existing muscle tissue. (This is why newcomer gains are so large.)
> If you feel like you're not improving, change something.
Just make sure you give it enough time to make sure it's truly a plateau (measured in weeks or months depending on how long you've been training). Bouncing around to a new barbell program every 2 weeks will do you little to no good.
Agree with the comments that this seems to confirm what was already known. (Though if there was no previously published confirmation, then the paper is still relevant.)
Two things about the methodology leave me wondering. They gave a 50-pound prize to the top performer on the mental fatigue tests. Couldn't this work against the study as a demotivator? I'm thinking in particular of the other studies showing monetary rewards have a negative performance effect on demanding cognitive tasks.
Second, why neutral mood documentaries? Neutral mood doesn't to me make something obviously not mentally demanding. It does sound relatively lower mental effort, but as a research paper methodology, it doesn't seem to prove it, and I feel like there are better options. Why not meditate, for example, or just lie down for an hour listening to soothing beach sounds or something like that?
This is quite different from something that is familiar to athletes, namely that low blood sugar can get you to lose mental focus and coordination to perform your best.
Here, the test subjects were simply subject to some cognitive loading.
Nothing "doh, obvious" about this.
We know that there is a connection between mental alertness and muscle coordination and drive, but it's not obvious that these can be eroded simply by cognitive activity; essentially a "software" problem.
Interesting. I started biking to/from work and was wondering why going home always felt harder. I suspected it was because my body was a bit tired just from being awake for the past ~8 hours (desk job, so not the work itself) but I never considered mental fatigue to play a part.
I wonder if this extends into the positive as well, do cognitive boosting drugs (nootropics?) enhance your performance.
> I wonder if this extends into the positive as well, do cognitive boosting drugs (nootropics?) enhance your performance.
Yes. Dextroamphetamine is considered a PED and is banned in (some? all?) professional sports. The Orioles' slugger Chris Davis was suspended a couple years ago for using it. But it is a CNS drug; I believe it is most commonly prescribed to people with ADHD, to improve their focus.
That is their assumption, but I'm not sure they really can say that. I notice that they didn't measure cortisol, which seems odd.
When you exercise, the increase in cortisol results in a 50% increase in endurance compared to if there was no cortisol increase, at least in rat experiments [1].
Given that cortisol is involved in both mental alertness and physical endurance, it seems like it could be a plausible reason for this finding.
Please don't post drive-by dismissals to Hacker News. Even if you're right and the article is worthless, it degrades the quality of the discussions here and signals the wrong things. And if you're wrong, i.e. if the article has value and you missed it, then you're really damaging the thread.
In such a case, please either flag the article and move on, or post something substantive about its specifics.
You saw the headline, but you might have missed the second sentence of the abstract: “Although the impact of mental fatigue on cognitive and skilled performance is well known, its effect on physical performance has not been thoroughly investigated.”
Even if the overall idea is obvious, these effects are good to validate and quantify.
For instance, this is a bit less obvious: “[...] physiological responses to intense exercise remained largely unaffected. Self-reported success and intrinsic motivation related to the physical task were also unaffected by prior cognitive activity. [...] our study provides experimental evidence that mental fatigue limits exercise tolerance in humans through higher perception of effort rather than cardiorespiratory and musculoenergetic mechanisms.”
It would be interesting to do follow-up studies with larger groups of participants to figure out how much variation there is in the effect between different people, or whether there are any ways to reduce the subjective impression of effort to mitigate the apparent throttling effect of mental fatigue.
Even so it's important to have been researched. Where exercise (or nutrition, for that matter) is concerned many statements floating around the internet in particular sound entirely logical - including a lot of false ones.
Absolutely; common knowledge becomes scientific knowledge (or is refuted) by experiment and reproducibility. You can go too far in rejecting old wives' tales (like how, in their discovery of vitamin A, the Japanese initially ignored the popular wisdom that buckwheat noodles prevent beriberi), but you can obviously go too far in accepting them as well.
This was shown in the last episode of Arrow. Oliver was so mentally distraught over Felicity breaking up with him that he couldn't physically beat Vandal Savage, and all of Central City was destroyed.
Maybe he was, but you just totally spoiled it for everyone who doesn't get to see the latest episodes the moment they air. A lot of us outside the US don't even get the "current" season yet. Warning next time, please?
