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Fitness Theory and Practice. CrossFit's rationale & foundations. Who is fit? What is fitness?

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Old 09-19-2009, 02:28 PM   #1
Daniel Gam
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high intensity exercise bad for you?

i was just studying for my physiology test and i came across this excerpt from the vander's human physiology, a fairly reputable physiology textbook.

"During maintained contractions, once the contracting muscles exceed 10-15 percent of their maximal force, the blood flow to the muscles is greatly reduced because the muscles are physically compressing the blood vessels that run through them ... frequent exposure of the heart to only this type of exercise can cause maladaptive changes in the left ventricle, including wall hypertrophy and diminished chamber volume."

(basically, hard work is bad for you ...)

what i want to know is what kind of research and/or assumptions led to that kind of statement.
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Old 09-19-2009, 02:40 PM   #2
Jared Ashley
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Re: high intensity exercise bad for you?

Looks to me like it's saying that ONLY strength training, without some accompanying metcon/cardio can bad for you. that's really not news.
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Old 09-19-2009, 03:56 PM   #3
William Jackson
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Re: high intensity exercise bad for you?

sounds false. the wording sounds medical enough but i really dont see this as true. 10-15% of contractile force? what about a child learning to walk/crawl? infants and toddlers have very little strength and i imagine that the early stages of locomotion are spent abouve 10-15% of contactile force yet they are fine. and as far as heart hypertrophy, the only athletes ive heard of this being a cause of death is with long distance runners, not weightlifters who spend much more time at i higher muscular "contractile" force

i am not a doctor nor play one on tv but the knowledge i have gathered through living life tells me not to believe this. just remember it until you take the test
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Old 09-19-2009, 04:42 PM   #4
Lincoln Brigham
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Re: high intensity exercise bad for you?

You need to find out what is meant by "maintained contractions". 10 seconds? 1 minute? All day? I suspect Vander means a mild contraction (10-15%) that last throughout the waking day.

Chronic contraction of the muscles, aka "bracing", is well known to cause a host of problems. "Constant, chronic, muscle tension that is usually below the level of conscious awareness, limiting blood supply to important parts of the body."* This is the polar opposite of short bouts of hard work.

*http://askwaltstollmd.com/wwwboard/g...b.html#Bracing
link is work/family safe.
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Old 09-20-2009, 05:39 PM   #5
Donald Lee
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Re: high intensity exercise bad for you?

Quote:
Originally Posted by Daniel Gam View Post
i was just studying for my physiology test and i came across this excerpt from the vander's human physiology, a fairly reputable physiology textbook.

"During maintained contractions, once the contracting muscles exceed 10-15 percent of their maximal force, the blood flow to the muscles is greatly reduced because the muscles are physically compressing the blood vessels that run through them ... frequent exposure of the heart to only this type of exercise can cause maladaptive changes in the left ventricle, including wall hypertrophy and diminished chamber volume."

(basically, hard work is bad for you ...)

what i want to know is what kind of research and/or assumptions led to that kind of statement.
I doubt 10-15% is correct. I have heard that beginning at about 40% of maximal muscular contractions blood flow to muscles significantly reduces.

As far as the left ventricle hypertrophy, that's common knowledge. There's not much to debate there. I don't think chamber volume diminishes though. In sedentary individuals, strength training provides many cardiovascular benefits usually attributed to aerobic exercise. It is probably more difficult to expand your chamber volume if you have much left ventricle hypertrophy though.
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Old 09-20-2009, 08:02 PM   #6
Jacob Cloud
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Re: high intensity exercise bad for you?

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Originally Posted by Donald Lee View Post
It is probably more difficult to expand your chamber volume if you have much left ventricle hypertrophy though.

I'd be interested in hearing more about this, because I've only seen loose discussion of it in the past.
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Old 09-21-2009, 04:02 AM   #7
Amir Fazeli
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Re: high intensity exercise bad for you?

The heart changes in size as part of adaptation to exercise. There are two types of heart muscle hypertrophy, eccentric and concentric hypertrophy. The difference is as follows:

- Eccentric hypertrophy is the type that comes about from aerobic exercise. When we undertake long-term aerobic exercise the adaptation the heart makes is the left ventricle gets bigger by adding myosin chains in series making the muscle structure of the wall lengthen. This means the left ventricle can fill with more blood, ultimately increasing stroke volume.


- when we undertake long-term anaerobic exercise we cause heart muscle hypertrophy in a different way, we add new myosin chains in parallel form to the left ventricle wall, i.e. we pack on new layers ultimately making the wall thicker, but outwards, so we keep the same filling space within the left ventricle for blood to pour in. This happens because of the increase in resistance to blood flow due to compressed vessels as you mentioned. The heart needs to adapt to be able to push blood out with more force and this is how it does it. This is concentric hypertrophy. This heart can produce much greater pressures than the aerobic athletes heart, however the SV doesnt change much or as much as an aerobic athlete's heart would. This is the type of heart olympic weight lifters would have.

the bad type of hypertrophy is pathological hypertrophy where the heart does get bigger through some muscle gain and mostly collagen buildup, the extra muscle is really useless anyway and it seems to grow from the outside in, ultimately causing the left ventricle filling space to decrease. Causing the decrease in stroke volume. This comes about from hypertension and heart disease.

Hope that explains it.
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Old 09-21-2009, 04:38 AM   #8
Greg Privitera
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Re: high intensity exercise bad for you?

Great explanation, thank you Amir.
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Old 09-21-2009, 09:11 AM   #9
Jacob Cloud
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Re: high intensity exercise bad for you?

Quote:
Originally Posted by Amir Fazeli View Post
The heart changes in size as part of adaptation to exercise. There are two types of heart muscle hypertrophy, eccentric and concentric hypertrophy. The difference is as follows:

- Eccentric hypertrophy is the type that comes about from aerobic exercise. When we undertake long-term aerobic exercise the adaptation the heart makes is the left ventricle gets bigger by adding myosin chains in series making the muscle structure of the wall lengthen. This means the left ventricle can fill with more blood, ultimately increasing stroke volume.


- when we undertake long-term anaerobic exercise we cause heart muscle hypertrophy in a different way, we add new myosin chains in parallel form to the left ventricle wall, i.e. we pack on new layers ultimately making the wall thicker, but outwards, so we keep the same filling space within the left ventricle for blood to pour in. This happens because of the increase in resistance to blood flow due to compressed vessels as you mentioned. The heart needs to adapt to be able to push blood out with more force and this is how it does it. This is concentric hypertrophy. This heart can produce much greater pressures than the aerobic athletes heart, however the SV doesnt change much or as much as an aerobic athlete's heart would. This is the type of heart olympic weight lifters would have.

the bad type of hypertrophy is pathological hypertrophy where the heart does get bigger through some muscle gain and mostly collagen buildup, the extra muscle is really useless anyway and it seems to grow from the outside in, ultimately causing the left ventricle filling space to decrease. Causing the decrease in stroke volume. This comes about from hypertension and heart disease.

Hope that explains it.

Amir, thanks for typing this, it's very helpful.

So does this back up some people's statements that it is better (I use the term loosely and am referring to general CF-type recreational athletes) to do some amount of LSD work before getting into heavy strength/anaerobic programs?

My concern is that, with no background in LSD training at all, and some amount of heavy lifting, I find it VERY hard/taxing to try and improve such simple aerobic things as my 1 mile time. Did I lift too much, too early?

Of course, I'm also fat and have a family history of heart problems, so who knows. But it's interesting reading.
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Old 09-22-2009, 02:19 PM   #10
Ben Moskowitz
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Re: high intensity exercise bad for you?

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Originally Posted by Lincoln Brigham View Post
You need to find out what is meant by "maintained contractions". 10 seconds? 1 minute? All day? I suspect Vander means a mild contraction (10-15%) that last throughout the waking day.

Chronic contraction of the muscles, aka "bracing", is well known to cause a host of problems. "Constant, chronic, muscle tension that is usually below the level of conscious awareness, limiting blood supply to important parts of the body."* This is the polar opposite of short bouts of hard work.

*http://askwaltstollmd.com/wwwboard/g...b.html#Bracing
link is work/family safe.
Does this mean that contracting your upper back muscles for posture's sake - moving the scapula back and down - is bad?
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