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Posted (edited)
I'm reading this article, which arrives at the following conclusion:

 

Quote

 

As aerobic exercise will undoubtedly increase the metabolic rate in the body, the harmful effects of exercise and exercise-induced ROS are well documented. Exercise localized to a peripheral muscle group in COPD patients has been shown to induce systemic oxidative stress [118]. Acute exercise-induced oxidative stress contributes to post-exercise proteinuria in untrained rats [119]. A maximal bicycle exercise results in DNA strand breaks and oxidative DNA damage [120]. High-competition swimming imposes high and sustained oxidative and proteolytic stress on adolescents, which may increase potential risk of cardiovascular disease in the future [121]. A run-to-exhaustion exercise leads to an increase in oxidative damage of lymphoid tissues in rats [122].

In summary, strenuous exercise under conditions of disease or overtraining would significantly elevate respiration rate, lead to a dramatic and sustained increase in ROS that is more than the antioxidant defence system can scavenge, and eventually result in oxidative stress and damage to physiological functions. Therefore, though regular exercise is important to improve cardiorespiratory fitness, extreme or exhaustive physical activities should be avoided, especially under certain disease conditions.

 

 

My questions are:
 
#1 Is this a legitimate conclusion and
#2 if it is, what is "extreme or exhaustive" physical activity which could achieve this overproduction of ROS above the body's antioxidant defense? What level of exercise are we talking about?
 
I've just never heard of exercise potentially being detrimental to health, so I'm a little shocked. It goes against all advice you ever hear throughout your life where exercise is presented as an unqualified good.
Edited by Alfred001
Posted

As with virtually all biological systems an one-dimensional view is not helpful. Yes, higher metabolic rate means higher rate of ROS generation. It also means that the system needs to ramp up its antioxidative defenses to cope. How much it can do so, is dependent on many, many factors. Then if the defenses are overwhelmed and damages happen on the cellular level, you then would have to look at how much of the tissue can be repaired. And then you go even higher to the systemic level and ask about health detriment/benefit, you then need to balance out those damages with all the benefits you get from activity.

Ultimately oxidative damages will accumulate, regardless of exercise level. But we also know that without exercise the risk of cardiovascular and other failures increase. Extreme exercise can be detrimental, but I suspect it is less due to oxidative damages but more to injuries and other effects of regular overexertion.

Posted (edited)
1 hour ago, Alfred001 said:
I'm reading this article, which arrives at the following conclusion:

 

 

My questions are:
 
#1 Is this a legitimate conclusion and
#2 if it is, what is "extreme or exhaustive" physical activity which could achieve this overproduction of ROS above the body's antioxidant defense? What level of exercise are we talking about?
 
I've just never heard of exercise potentially being detrimental to health, so I'm a little shocked. It goes against all advice you ever hear throughout your life where exercise is presented as an unqualified good.

Then you are poorly informed. Any sports trainer who is any good will be careful about red-lining it. Most training regimes are largely aerobic and do not proceed to exhaustion. I have rowed most of my life and even rowing training is a controlled mix of exercise that is mainly aerobic. We were also told never to train if we were not feeling well. It has been known for decades that training when you have flu can give you irreparable heart damage for example. 

Edited by exchemist
Posted (edited)
On 8/31/2022 at 7:28 PM, CharonY said:

As with virtually all biological systems an one-dimensional view is not helpful. Yes, higher metabolic rate means higher rate of ROS generation. It also means that the system needs to ramp up its antioxidative defenses to cope. How much it can do so, is dependent on many, many factors. Then if the defenses are overwhelmed and damages happen on the cellular level, you then would have to look at how much of the tissue can be repaired. And then you go even higher to the systemic level and ask about health detriment/benefit, you then need to balance out those damages with all the benefits you get from activity.

Ultimately oxidative damages will accumulate, regardless of exercise level. But we also know that without exercise the risk of cardiovascular and other failures increase. Extreme exercise can be detrimental, but I suspect it is less due to oxidative damages but more to injuries and other effects of regular overexertion.

Of course, no one is saying exercise is detrimental and perhaps even with strenuous exercise the net effect is beneficial, but the question becomes can you hit some sweet spot of intensity where you're getting the benefits while eliminating or minimizing the ROS generation so that you maximize the net benefit and avoid any potential drawbacks.

Which poses the question of, as you move the intensity slider from low to high, how do the benefits change and how does the ROS generation change. Meaning do the benefits keep increasing with intensity and at what point of intensity do you hit a level of ROS generation that the antioxidant system can't handle. Where is the sweet spot? Is anyone aware of any research looking into this question?

And it may be a relevant question, because perhaps exercise, once you cross a certain threshold of intensity, yes, reduces your risk of cardiovascular disease, but because of the oxidative damage, increases your risk of cancer. I mean, afterall, they do say

Quote

A maximal bicycle exercise results in DNA strand breaks and oxidative DNA damage [120].

Edited by Alfred001
Posted
3 hours ago, Alfred001 said:

but the question becomes can you hit some sweet spot of intensity where you're getting the benefits while eliminating or minimizing the ROS generation so that you maximize the net benefit and avoid any potential drawbacks.

The theoretical answer is probably yes, the practical almost certainly no. The effects of exercise are very complex and while there is some rough understanding on the macro level (e.g. on average what level of exercise seems to correlate with a certain outcome) but what is really happening mechanistically is barely understood. Pretty much the same can be said for respiration rate, generation of ROS and all the factors that may account not only for individual differences but potentially also day-to-day differences in a given person. Slept badly? It may or may not influence your metabolism in terms of ROS generation. 

Moreover, we also do not understand relative contribution to a given factor very well. Are exercise benefits on cardiovascular health offset by eating bacon once? How about twice? Weekly?

Again, individual differences are huge and as we age, or get stressed, a lot in our physiology changes. Trying to achieve the level of desired precision with the lack of data we have got is simply put impossible. Only folks like Dr. Oz and their ilk will tell you that we have clear and definite answers to that. What we do have are rough guidelines which apply to some degree to a population with a given set of characteristics. 

Pretty much everything beyond that is extrapolation.

Posted

Keep in mnd that the human body is 'adaptive'.
Unless you subject it to a stress that it cannot handle, it has no reason to adapt.

When I used to work out, the common belief was that, if you put a 6 HP load on a 5 HP machine, you blow the machine.
While if you put a 6 HP load on a 5 HP body, you eventually end up with a 6 HP body.

Posted
28 minutes ago, MigL said:

While if you put a 6 HP load on a 5 HP body, you eventually end up with a 6 HP body.

Or ligament issues. As you mentioned, biological systems are complex and they have the annoying tendency not to work precisely as predicted.

Posted
3 hours ago, MigL said:

Keep in mnd that the human body is 'adaptive'.
Unless you subject it to a stress that it cannot handle, it has no reason to adapt.

When I used to work out, the common belief was that, if you put a 6 HP load on a 5 HP machine, you blow the machine.
While if you put a 6 HP load on a 5 HP body, you eventually end up with a 6 HP body.

Cardiovascular fitness is not developed this way, though. That is done by long spells well within maximum capacity.

  • 4 weeks later...
Posted

If I remember correctly, this is a very old concept.

It was first proposed in an effort to explain a negative trend where long distance marathon runners suffered elevated levels of cardiovascular and heart issues. 

They tried to approach the topic from different angles. Maybe the tendency of long distance runners consuming greasy or oily food like pizza was partly responsible? Perhaps there was another cause? 

While a moderate amount of exercise could be healthy. It is also possible than exercise in extreme excess could stress human biology in ways which are unhealthy.

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