Physical fatigue is in the brain as much as in the body, 2022, Robson

Arnie Pye

Arnie Pye

Senior Member (Voting Rights)
An article from the website Psyche that didn't deserve it's own thread so I hope a mod will move it to where it should have been put.

Title : Physical fatigue is in the brain as much as in the body
Link : https://psyche.co/ideas/physical-fatigue-is-in-the-brain-as-much-as-in-the-body
Publication Date : 6th April 2022
Author : David Robson, science writer and author of The Expectation Effect (2022)

It is 18 July 1997, at stage 12 of the Tour de France, and Richard Virenque, of the French team Festina, is preparing for the 55-km individual time trial in Saint-Étienne. These trials aren’t his specialism and, having heard of a new drug that will supposedly deliver him a spurt of energy, he asks his physiotherapist, Willy Voet, to procure the ‘magic potion’.

Voet is soon in possession of a small jar of a mysterious white liquid, which he is told to inject into Virenque’s buttocks before the event. On race day, Voet faithfully delivers an injection – and the results are breathtaking. Virenque goes head-to-head with his great rival Jan Ullrich for much of the race. Although the German eventually wins, Virenque is only 3 minutes and 4 seconds behind him – a much better result that day than he could have imagined. ‘God I felt good!’ he later told Voet. ‘That stuff’s just amazing.’

Little did Virenque know that there was no active ingredient in the magic potion. Before delivering the injection, Voet – who feared trying a new substance mid-tournament – had swapped the mysterious white substance for a glucose solution. ‘There is no substitute for self-belief,’ the physiotherapist would later write in his autobiography, Breaking the Chain (2001).
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So, an extremely fit and healthy athlete was taking part in the Tour de France. He was given a placebo, and it helped him a lot. There is no mention of how Virenque felt during the following week, two weeks, month etc, to see if he developed any problems as a result of increasing his exertion levels over what was normal for him, but he was already fit and wasn't ill so he would probably have recovered fairly quickly.

There has been lots of research done on placebos showing that they "work" for some people. The n = 1 anecdote above doesn't really add to the literature.

Yet a series of puzzling findings over the past two decades suggests that it cannot be so simple. For instance, in one study, researchers used electrodes attached to subjects’ arms and legs to show that only 35-60 per cent of muscle fibres appear to be operating during prolonged or intense exercise. If biochemical changes in muscle fibres were the sole cause of physical fatigue, you’d expect many more of the fibres to have been recruited to share the burden before we reach exhaustion. But that doesn’t seem to be what happens.
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That percentage suggests that anyone who was tested wasn't putting ALL their effort into the prolonged or intense exercise. And why should they be expected to? In order to survive I would expect people to keep something in reserve in case they were about to be chased by a saber tooth tiger or a threatening person with a big knife.

Stories of people performing incredible feats of strength in order to save a loved child or spouse crop up quite frequently. But would anyone be able to do this if they had just used up all their energy? It makes sense to me that people would hold something back when exercising. And for those people who are ill holding something back may well increase their odds of survival.
 
Every time I see the general argument of "the mind can X", I can only think of the fact that the Moon can fall on the Earth. It definitely won't because of its orbital alignment and mechanics, but if it had a different orbital alignment, it could, which means it can, it is feasible, possible. If the basis of an idea is that if it's possible, even if 1 chance in a quadrillion, as long as you can't disprove it, it means that it can be assumed to be the case, then that idea is either completely worthless, or pure fiction.

Still, Moonfall is just as much fiction as Reefer madness is just as much fiction as this placebo/nocebo nonsense is. It's the ultimate in failing at statistics.
 
I read about this in a rather confused article in the New Scientist. There was a lot about marathon runners being exhausted if they did not know about a hill at the end of a race but managing if they knew beforehand. Then they spoke about cyclists who took cocaine but then died of a heart attack during the race.

What was obvious is that our sense of fatigue is vital to protect our hearts from over exertion.

If you think you have been given a magic drug you are more likely to ignore fatigue and not pace your exercise the same way as you would. There are much more plausible things that could explain placebos than magic thinking.
 
Little did Virenque know that there was no active ingredient in the magic potion. Before delivering the injection, Voet – who feared trying a new substance mid-tournament – had swapped the mysterious white substance for a glucose solution.
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strategist said:
That is quite possibly not a placebo.
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Arnie Pye said:
Can you explain please? I would have thought that injections of glucose are not a very good or safe way of increasing energy in healthy people.
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Glucose is definitely an active ingredient. One possibility (I don't know if this is feasible):

It's a white liquid that is injected into the buttocks. It is said to be a "glucose solution" and "placebo". One of the rate-limiters for competitive cycling is glucose delivery to muscles. Ongoing carb refreshing is required to feed the engine.

Perhaps it is not immediately absorbed to the blood stream on injection (and shunted off to the liver as glycogen). Then, it could be liberated from depot and made available more continuously during the act of cycling. Liberating glucose would thereby help keep serum levels and muscle glucose supply optimal over a longer time period.

Not sure if there's a way of injecting glucose in a suspension that tends to hold it longer at the depot site. This was a 55 km stage, so probably around 2 hours, depending on hills, so that may not even be relevant.

Either way, perhaps there would be a lesser effect if it had been injected eg into the deltoids instead of gluteals, as upper limbs don't move anywhere near as much.
 
Besides labelling glucose a placebo in context of sport, this is also a n=1 story where something very ordinary happens (one cyclist performs better than another) that is then interpreted as supporting conclusions that don't really follow from the observation (the cyclist performed better because he believed he had an advantage). And if the cyclist hadn't performed better, it would not have been interpreted as a failure of a placebo to increase performance.
 
Slipping into conspiracy territory but you can't believe everything you read, unfortunately, even scientific papers. A quick read of "The Dark Psychosomatic History" series of blog posts (https://mecfsskeptic.com/the-dark-psychosomatic-history-of-heart-disease-part-i/) shows that.

Talking about placebos in sport could easily be a cover up for doping.

A BPS proponent compared us unfavourably with Lance Armstrong who had cancer but exercised himself back to health until he was winning tournaments. If only we had his mental strength and determination. If only he had not taken performance enhancing drugs.
 
Arnie Pye said:
That percentage suggests that anyone who was tested wasn't putting ALL their effort into the prolonged or intense exercise. And why should they be expected to? In order to survive I would expect people to keep something in reserve in case they were about to be chased by a saber tooth tiger or a threatening person with a big knife.
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That finding is completely normal and expected. Noakes doesn't seem to appreciate that the rate limiting factor for sustained performance is oxygen delivery and VO2Max occurs at well below 100% muscle fibre recruitment.

Noakes seems to be making much ado about difference in pacing of athletes - yes you can exercise past VO2Max, but for how long? It is simply about about appropriate pacing, but he seems to want to add a bunch of mysticism about the brain.

Individuals can only recruit close to 100% of the muscle mass for short periods of time <30 seconds (and maximal workrate cannot be sustained for more than 10 seconds). This is where you see those big power outputs of professional cyclists during sprints of 1500-2000w.

Pushing past this will lead to rapid acidification and rapidly burn through the glycogen stores of energy in the muscle. It will also generate central fatigue due to afferent feedback which inhibits the excitability of the motor cortex. This is NOT about "whole body homeostasis" as Noakes suggests, but the homeostasis of the specific muscle groups being utilised. The underlying (evolutionary) reason is a need to provide some performance to escape danger. It also isn't a hard stop signal (performance failure) as Noakes suggests, as individuals can and do push past until they "hit the wall" (glygogen depletion).

A key point is this central fatigue that works to reduce output works independently of motivation. There is no evidence for the following being important:

There seems little doubt that the conventional view was partly correct and that the brain is constantly taking note of physical changes using sensors throughout the body. But, importantly, it will then combine that information with memories of previous experiences, current mood, social feedback – and its estimates of the challenges to come.
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We know this because the afferents can be blocked and the central fatigue disappears (but it also leads to insufficient ventilation, which means increased metabolic fatigue - no overall performance is gained)

Studies also show that stimulants like caffeine (or increased adrenaline) don't improve VO2Max and hence won't actually improve sustained performance. https://journals.sagepub.com/doi/abs/10.1177/0260106017723547


Fatigue is not an "emotion" (as suggested by Noakes) used to regulate exercise performance. The sensations associated with fatigue are a warning signal that performance itself is likely to be reduced.

Mithriel said:
A BPS proponent compared us unfavourably with Lance Armstrong who had cancer but exercised himself back to health until he was winning tournaments. If only we had his mental strength and determination. If only he had not taken performance enhancing drugs.
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Lance Armstrong's effective blood doping shows us that oxygen transport (and blood volume) is indeed the major factor in limiting sustained performance during cycling.
 
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Honestly anyone who watches even a bit of sport is well aware of how random performance can be. Some professional athletes can go on weeks' or months' long streaks of high performance, then drop down to barely contributing. The reasons for that are numerous, often small injuries that take that leading edge full health gives them, especially as high levels of performance are simply not measurable or understandable.

Oversimplistic thinking always leads to simple-but-wrong answers to complex issues.
 
rvallee said:
Honestly anyone who watches even a bit of sport is well aware of how random performance can be. Some professional athletes can go on weeks' or months' long streaks of high performance, then drop down to barely contributing. The reasons for that are numerous, often small injuries that take that leading edge full health gives them, especially as high levels of performance are simply not measurable or understandable.

Oversimplistic thinking always leads to simple-but-wrong answers to complex issues.
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Agreed.
Optimum pacing is tricky, it is why professional athletes usually have a crew of support staff.
 
And, frankly, is the main reason sports are impressive. Seeing machines built specifically to accomplish a task? Boring. They literally can't do it differently, unless broken.

Human performance is so difficult to achieve, that's what makes it all worth watching. It's so hard to not only attain a high level of performance, but sustain it over the long term. If it were predictable, it would get boring. So variation is baked in the process, is basically the norm.
 
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