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The more exercise the better. Profound effects of aerobic fitness


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"Conclusions and Relevance  Cardiorespiratory fitness is inversely associated with long-term mortality with no observed upper limit of benefit. Extremely high aerobic fitness was associated with the greatest survival and was associated with benefit in older patients and those with hypertension. Cardiorespiratory fitness is a modifiable indicator of long-term mortality, and health care professionals should encourage patients to achieve and maintain high levels of fitness."

I find these conclusions completely unsupported by the study. While there is a relationship between cardiorespiratory fitness and exercise, it is not as straightforward. There is some difference between CRF in unexercised people - some are just more naturally fit than others, even without exercise. When I was in my 20's, I did not exercise, but maintained excellent muscle tone, which always amazed my friends who exercised - it's the same with CRF, it varies. Point number two - people respond differently to exercise, while the majority gain in CRF the more they exercise, there is a minority (I believe I read it was about 20%) do not respond. 

But the most important problem with this conclusion is that it by design *cannot* prove causality. What they observed is that the more CRF a cohort was, the lower their mortality. However all that says to me is that some people have bodies/physiologies which are suited for extreme exercise - generally very healthy. If you are very healthy, it's not strange that your mortality will be low. It's a self-selecting group. Others may want to achieve high CRF and simply be unable to because they either don't respond to exercise or are not naturally healthy enough to become elite athletes. Therefore encouraging people to exercise is pointless if they are unfit because they don't respond to exercise or because their bodies can't take it. 

Had this been a study where they divided people RANDOMLY into groups of none-low-high-extreme exercise and then collated the results, then the conclusion would be valid. But as it stands, all that we found out is that some people have physiological pre-dispositions to respond to excercise in the extreme and are super healthy to begin with.

So for me the above CONCLUSION = unsupported and RELEVANCE = none.

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Hi Tom!

It isn't quite that simple.  A person who hasn't exercised for years won't be able to do intense cardio exercise.  But person X can do a 10 minute mild cardio exercise several days a week (e.g., elliptical cross-trainer set at the lowest tension (usually number 1)).   Then slowly work up, over a year or more to longer exercise intervals at higher resistance levels.  Inevitably becoming a vigorous aerobic exerciser for say 30 minutes daily, five days a week.  (That's the level recommended by Luigi Fontana.)

  --  Saul 

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4 minutes ago, Saul said:

Hi Tom!

It isn't quite that simple.  A person who hasn't exercised for years won't be able to do intense cardio exercise.  But person X can do a 10 minute mild cardio exercise several days a week (e.g., elliptical cross-trainer set at the lowest tension (usually number 1)).   Then slowly work up, over a year or more to longer exercise intervals at higher resistance levels.  Inevitably becoming a vigorous aerobic exerciser for say 30 minutes daily, five days a week.  (That's the level recommended by Luigi Fontana.)

  --  Saul 

All that is quite true for most people. But not all. As I said, there is a minority (approx. 20%) that doesn't respond to exercise - in which case starting slow simply leads to nothing slowly - they don't improve, in fact, some actually do *worse* with exercise. We all know that people respond to exercise along a continuum - some extremely well at one end, and some not at all at the other and everything else in between. Starting slow does not help people who are non-responders.

The main take-away however, is that this study does not address the "health bias" - people might exercise with the intensity that is allowed by their body. Those whose bodies are so healthy that they can exercise at elite levels will do so. That does *not* mean that Joe Average can be - or indeed should be - pushed into the same level of exercise (however gradually). The only way to prove that is through an randomised prospective study. The present study merely tells us that those who exercise at an elite level have the lowest mortality - it says nothing about whether *everybody* is capable of exercising at that level in the first place, no matter how much they are encouraged. Indeed, a moment's thought tells us that this must be so, because after all, not all people can become elite athletes - some just have greater innate capacity... why would this not apply more broadly over a broader spectrum? 

Incidentally, I remember reading about a study about whether grip strength predicts health status. What they found is that grip strength *does* predict health status, but only if it is *unexercised* grip strength! If your grip got stronger because you exercised your hand muscles, it suddenly stopped being a good predictor of health status, because it no longer measured the innate capacity, it amounted to gaming the measurement. So too here - what if having the *potential/capacity* to become an elite athlete is what allows you to have lower mortality through innately healthier/sturdier physiology, and if you have no such innate capacity all the exercising in the world won't do you much good - same as Joe Average will never beat Olymic Gold medal records no matter how much they exercise. Good CRF might simply be a marker for a superior physiology and nothing more. Now, I don't think it's that extreme, but I do believe that the relationship is complex. Which is why I find the conclusions of this study to not be justified by what they measured.   

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I'm skeptical of your assertion:

15 hours ago, TomBAvoider said:

As I said, there is a minority (approx. 20%) that doesn't respond to exercise

Do you have any evidence to back up this assertion?  (It looks like the sort of thing a couch potato might use to justify hir lethargy.)

  --  Saul

  

  

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On 1/20/2019 at 1:59 AM, TomBAvoider said:

As I said, there is a minority (approx. 20%) that doesn't respond to exercise   

20% of people don't respond to exercise? 

Although all the studies showed people vary widely in their response:

https://www.ncbi.nlm.nih.gov/pubmed/26767377    Found that 7% of people were "low responders" to muscle strength training of just 2 days a week.

https://www.ncbi.nlm.nih.gov/pubmed/26854820    Found that over 20% people did not increase peak oxygen uptake after some studies on sprint interval training,  "No nonresponders for peak oxygen uptake were observed in studies where participants trained 4 times per week"

So while some people may have a week response and some may not train enough to have a response, that's a long way from 20% of people do not respond to exercise.

 

 

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At best, though, it’s going to be an asymptotic curve, right?

Most studies show you get at least 80% of the possible cardiovascular benefits with 150 minutes a week. 95-100% by 300.  Do lots if it’s fun, sure, but don’t think you really NEED to—and keep an eye on inflammation, too.

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