T Nation

Which Muscle Fiber Type Atrophies Faster?

[quote]Trapmaster wrote:

[quote]four60 wrote:

[quote]StormTheBeach wrote:

[quote]four60 wrote:
I must admit. I am confused. I just thought 2 muscle groups same size same density would diminish at the same rate. All things being equal.

I’m really curious to see a answer to this. I thought it was just all about how fast persons body would burn its energy sources.[/quote]

That would be true but type I and type II fibers are not the same size or density.[/quote]

So we are saying that its a training and not size that determines the 2 types?[/quote]

Done properly High rep training should result in more type I muscle fiber growth, whereas low rep training should result in type II muscle fiber growth, so yes it is determined by training, but size is also a factor but does not determine the type. Bodybuilders generally have larger muscles, due to type I muscle fibers having more potential for growth as well as holding more necessary fluids ie: glycogen, water etc. Type II muscle fibers are denser and are actually comprised of more actual muscle tissue but have less of a visual effect which I explained.

Still confused as to which atrophies faster.
[/quote]

From the sounds of it Type II would atrophies at a slower rate due to the density of the muscle fibers.
We are talking loss of muscle fibers and not just Size due to dehydration or loss of fat around the muscle.

[quote]Professor X wrote:

[quote]krebcycle wrote:

[quote]StormTheBeach wrote:
See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II’s? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.

[/quote]

Thanks for this. It’s been a while since we’ve had a real thought provoking intellectual on here.

Now if you could explain the ‘survival mechanism’ that causes sedentary people to have the ‘highest fibre area of type II’s’, it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.[/quote]

What he wrote isn’t exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution…as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.[/quote]

Yeah this is how I understand it. What I don’t understand is how being sedentary causes an adaption that leads to a profile high in type two fibres, which is what he has essentially said.

[quote]four60 wrote:

[quote]Trapmaster wrote:

[quote]four60 wrote:

[quote]StormTheBeach wrote:

[quote]four60 wrote:
I must admit. I am confused. I just thought 2 muscle groups same size same density would diminish at the same rate. All things being equal.

I’m really curious to see a answer to this. I thought it was just all about how fast persons body would burn its energy sources.[/quote]

That would be true but type I and type II fibers are not the same size or density.[/quote]

So we are saying that its a training and not size that determines the 2 types?[/quote]

Done properly High rep training should result in more type I muscle fiber growth, whereas low rep training should result in type II muscle fiber growth, so yes it is determined by training, but size is also a factor but does not determine the type. Bodybuilders generally have larger muscles, due to type I muscle fibers having more potential for growth as well as holding more necessary fluids ie: glycogen, water etc. Type II muscle fibers are denser and are actually comprised of more actual muscle tissue but have less of a visual effect which I explained.

Still confused as to which atrophies faster.
[/quote]

From the sounds of it Type II would atrophies at a slower rate due to the density of the muscle fibers.
We are talking loss of muscle fibers and not just Size due to dehydration or loss of fat around the muscle.[/quote]

Say you stop training completely because you are stuck on an island and starving to death. Your body is going to start eating your stored fat to live. Type I fibers have a shit load more stored fat than Type II. They would atrophy first. Say you stop training and still eat clean. There would be no need for your muscles to be big anymore because the stress from high volume training would be gone. No more need for large Type I fibers.

True, all fiber types would atrophy but when you returned to whatever your baseline is, you would have a much higher distribution of type II fibers.

[quote]StormTheBeach wrote:

[quote]Professor X wrote:

[quote]krebcycle wrote:

[quote]StormTheBeach wrote:
See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II’s? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.

[/quote]

Thanks for this. It’s been a while since we’ve had a real thought provoking intellectual on here.

Now if you could explain the ‘survival mechanism’ that causes sedentary people to have the ‘highest fibre area of type II’s’, it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.[/quote]

What he wrote isn’t exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution…as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.[/quote]

What if your low reps with high weight take 10 minutes a set? Like 5 reps with a 2 minute negative. And Extreme example but something to think about. The amount of reps with a given weight means absolutely nothing. The amount of force produced is the determining factor.[/quote]

So what about maxing out, grinding a rep?

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]Professor X wrote:

[quote]krebcycle wrote:

[quote]StormTheBeach wrote:
See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II’s? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.

[/quote]

Thanks for this. It’s been a while since we’ve had a real thought provoking intellectual on here.

Now if you could explain the ‘survival mechanism’ that causes sedentary people to have the ‘highest fibre area of type II’s’, it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.[/quote]

What he wrote isn’t exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution…as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.[/quote]

What if your low reps with high weight take 10 minutes a set? Like 5 reps with a 2 minute negative. And Extreme example but something to think about. The amount of reps with a given weight means absolutely nothing. The amount of force produced is the determining factor.[/quote]

So what about maxing out, grinding a rep? [/quote]

A true max effort is maximizing the amount of force you can produce=Training Type II Fibers

Old but a good one:

http://jhc.sagepub.com/content/32/2/146.short

“The lifters had a significantly greater content of mitochondria than the controls, which may suggest that inactivity rather than the lifting exercise contributes to a low volume-percent mitochondria and a high percentage of type IIB fibers.”

[quote]StormTheBeach wrote:

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]Professor X wrote:

[quote]krebcycle wrote:

[quote]StormTheBeach wrote:
See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II’s? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.

[/quote]

Thanks for this. It’s been a while since we’ve had a real thought provoking intellectual on here.

Now if you could explain the ‘survival mechanism’ that causes sedentary people to have the ‘highest fibre area of type II’s’, it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.[/quote]

What he wrote isn’t exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution…as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.[/quote]

What if your low reps with high weight take 10 minutes a set? Like 5 reps with a 2 minute negative. And Extreme example but something to think about. The amount of reps with a given weight means absolutely nothing. The amount of force produced is the determining factor.[/quote]

So what about maxing out, grinding a rep? [/quote]

A true max effort is maximizing the amount of force you can produce=Training Type II Fibers[/quote]

Not necessarily, it’s maximizing weight used, but not necessarily force. Some people (o-lifters) can actually create more force with lighter weight.

But I was asking because, type 2 is often associated with training explosively, but heavy weights are often done with much slower speeds and reasonably long times under tension.

I guess, you really need to brake type 2 down into more categories. I guess, I’m curious how well slow heavy reps activate the faster (type 2b) fibers.

[quote]krebcycle wrote:
Yeah this is how I understand it. What I don’t understand is how being sedentary causes an adaption that leads to a profile high in type two fibres, which is what he has essentially said.
[/quote]
He said that every time you train, the muscle will get used to oxidative work, unless you train for MAXIMAL force output (olympic lifters, olympic sprinters or so).

If you’re sedentary, you don’t give your muscles an incentive to be type I-like.
If you do a heavy snatch, you don’t give your muscles an incentive to be type I-like.
If you squeeezeadatop, guuuuud, you DO give your muscles an incentive to be type I-like.

My professor agrees with StormTheBeach. I personally don’t give a shit, but don’t be so sure that he’s wrong. It makes perfect sense after all.

[quote]StormTheBeach wrote:

[quote]Professor X wrote:

[quote]krebcycle wrote:

[quote]StormTheBeach wrote:
See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II’s? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.

[/quote]

Thanks for this. It’s been a while since we’ve had a real thought provoking intellectual on here.

Now if you could explain the ‘survival mechanism’ that causes sedentary people to have the ‘highest fibre area of type II’s’, it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.[/quote]

What he wrote isn’t exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution…as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.[/quote]

What if your low reps with high weight take 10 minutes a set? Like 5 reps with a 2 minute negative. And Extreme example but something to think about. The amount of reps with a given weight means absolutely nothing. The amount of force produced is the determining factor.[/quote]

Ten minutes a set would fall into “extended periods of time” just like I wrote.

Chances are, those who are able to grow the fastest yet have the weakest endurance are carrying more “fast twitch muscle fibers”.

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]Professor X wrote:

[quote]krebcycle wrote:

[quote]StormTheBeach wrote:
See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II’s? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.

[/quote]

Thanks for this. It’s been a while since we’ve had a real thought provoking intellectual on here.

Now if you could explain the ‘survival mechanism’ that causes sedentary people to have the ‘highest fibre area of type II’s’, it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.[/quote]

What he wrote isn’t exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution…as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.[/quote]

What if your low reps with high weight take 10 minutes a set? Like 5 reps with a 2 minute negative. And Extreme example but something to think about. The amount of reps with a given weight means absolutely nothing. The amount of force produced is the determining factor.[/quote]

So what about maxing out, grinding a rep? [/quote]

A true max effort is maximizing the amount of force you can produce=Training Type II Fibers[/quote]

Not necessarily, it’s maximizing weight used, but not necessarily force. Some people (o-lifters) can actually create more force with lighter weight.

But I was asking because, type 2 is often associated with training explosively, but heavy weights are often done with much slower speeds and reasonably long times under tension.

I guess, you really need to brake type 2 down into more categories. I guess, I’m curious how well slow heavy reps activate the faster (type 2b) fibers. [/quote]

Slow heavy reps DO NOT activate type II fibers at all. Weight used DOES NOT MATTER unless it is maximal. Because then maximal force is being produced. Moving light objects fast trains type II fibers AS LONG AS YOU ARE MOVING WITH MAXIMUM FORCE. Again, weight does not matter. Force does.

You completely contridicted yourself “its maximizing the weight used, not force. but o-lifters can create more force with lighter weights.” That doesn’t make any sense.

[quote]StormTheBeach wrote:

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]Professor X wrote:

[quote]krebcycle wrote:

[quote]StormTheBeach wrote:
See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II’s? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.

[/quote]

Thanks for this. It’s been a while since we’ve had a real thought provoking intellectual on here.

Now if you could explain the ‘survival mechanism’ that causes sedentary people to have the ‘highest fibre area of type II’s’, it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.[/quote]

What he wrote isn’t exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution…as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.[/quote]

What if your low reps with high weight take 10 minutes a set? Like 5 reps with a 2 minute negative. And Extreme example but something to think about. The amount of reps with a given weight means absolutely nothing. The amount of force produced is the determining factor.[/quote]

So what about maxing out, grinding a rep? [/quote]

A true max effort is maximizing the amount of force you can produce=Training Type II Fibers[/quote]

Not necessarily, it’s maximizing weight used, but not necessarily force. Some people (o-lifters) can actually create more force with lighter weight.

But I was asking because, type 2 is often associated with training explosively, but heavy weights are often done with much slower speeds and reasonably long times under tension.

I guess, you really need to brake type 2 down into more categories. I guess, I’m curious how well slow heavy reps activate the faster (type 2b) fibers. [/quote]

Slow heavy reps DO NOT activate type II fibers at all. Weight used DOES NOT MATTER unless it is maximal. Because then maximal force is being produced. Moving light objects fast trains type II fibers AS LONG AS YOU ARE MOVING WITH MAXIMUM FORCE. Again, weight does not matter. Force does.

You completely contridicted yourself “its maximizing the weight used, not force. but o-lifters can create more force with lighter weights.” That doesn’t make any sense.[/quote]

maxing out I meant maxing out on weight used. That may actually be sub-maximal force. O-lifters can generate max force by accelerating small(er) weights. An o-lifter maxing out weight on a deadlift may generate lower force in the same muscles than they do using a smaller weight in the clean. I’m just curious about the physiological differences.

My experience says type II… You use it infrequently in life. I am not due to lift until January… That’s depressing. :frowning:

Oh but I have a plan, yes I do. And I can’t wait to implement. I figure I can get 90% strength back in 6 weeks or less.

Coming off of my second intestinal virus in a month, that shit turns you to mush in days… But the plan. Heal damn it!

I believe StormTheBeach is saying that the percentage of Type II fibers relative to total fibers is more in non-lifters due to the fact that they never really trained to acquire Type 1 fibers, but Type 2 fibers can develop just from necessity in every day life.

Whereas somebody who trains primarily for hypertrophy (a bodybuilder) would have a higher percentage of Type I fibers relative to total fibers (due to the fact that they actually have developed Type I fibers and they are now actually a percentage of total fibers).

I tried to oversimplify things, but this makes more sense to me - not sure if true…

seems we need some basic physics

F=ma

for a barbell with a mass of m, on a planet with constantant of gravitation g, and a lifter exerting a force of L

L-mg=ma

L=m(a+g)

it should now be obvious that a big L can be atcheived either with a big mass or acceleration

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]DoubleDuce wrote:

[quote]StormTheBeach wrote:

[quote]Professor X wrote:

[quote]krebcycle wrote:

[quote]StormTheBeach wrote:
See, with the stupid methods most use to train, the fiber distribution of a bodybuilder and powerlifter would in most cases be very similar. And both would be similar to endurance athletes as well. You know who has the highest fiber area of type II’s? Sedentary people and olympic sprinters. Its a survival mechanism. The body adapts to the stress that is placed on it.

Lift weights for hours at a time and do a shit load of volume, your type I, slow oxidative fibers, will hypertrophy. Do high force speed work and high force maximal efforts and your type II fibers will be trained. Type II fibers are ONLY activated in training when utilizing those methods. The only time they are activated in real life? Life or death situations. Fight or flight. As a means of survival, type II fibers are much MUCH slower to atrophy. Just in case you get attacked by a bear or a fucking dinosaur tries to eat you.

[/quote]

Thanks for this. It’s been a while since we’ve had a real thought provoking intellectual on here.

Now if you could explain the ‘survival mechanism’ that causes sedentary people to have the ‘highest fibre area of type II’s’, it would be much appreciated. I was thinking about including some sitting down in front of the tv work in my next program. This has spurred me on.[/quote]

What he wrote isn’t exactly right.

Your type II muscle fibers are the focus whenever training with low reps and high weight. They are not just a survival mechanism though he is right that sprinters would likely have a larger distribution…as do well known bodybuilders, huge football players and people who can max out with huge weights but would falter if they had to do those reps for extended periods of time.[/quote]

What if your low reps with high weight take 10 minutes a set? Like 5 reps with a 2 minute negative. And Extreme example but something to think about. The amount of reps with a given weight means absolutely nothing. The amount of force produced is the determining factor.[/quote]

So what about maxing out, grinding a rep? [/quote]

A true max effort is maximizing the amount of force you can produce=Training Type II Fibers[/quote]

Not necessarily, it’s maximizing weight used, but not necessarily force. Some people (o-lifters) can actually create more force with lighter weight.

But I was asking because, type 2 is often associated with training explosively, but heavy weights are often done with much slower speeds and reasonably long times under tension.

I guess, you really need to brake type 2 down into more categories. I guess, I’m curious how well slow heavy reps activate the faster (type 2b) fibers. [/quote]

Slow heavy reps DO NOT activate type II fibers at all. Weight used DOES NOT MATTER unless it is maximal. Because then maximal force is being produced. Moving light objects fast trains type II fibers AS LONG AS YOU ARE MOVING WITH MAXIMUM FORCE. Again, weight does not matter. Force does.

You completely contridicted yourself “its maximizing the weight used, not force. but o-lifters can create more force with lighter weights.” That doesn’t make any sense.[/quote]

maxing out I meant maxing out on weight used. That may actually be sub-maximal force. O-lifters can generate max force by accelerating small(er) weights. An o-lifter maxing out weight on a deadlift may generate lower force in the same muscles than they do using a smaller weight in the clean. I’m just curious about the physiological differences.[/quote]

It actually makes perfect sense. Acceleration is the key word for the Olympic lifter. Although he is using lighter weight, he is moving it faster.

There is a lot of stuff being left out here. There are three types of muscle fibers, TypeI= endurance, TypeIIa=move shit fast and/or heavy and TypeIIb=move shit faster and/or heavier or you will die.

There is also muscle type density, with sacroplasmic ie… bodybuilder muscles being made up of more water than myofibril ie… oly lifter muscles.

I know this is wiki, but still explains it okay.

The bodybuilder will shrink faster due to the decrease in swelling from fluid, verus the oly lifters actual fiber density shrinking.

I think. But I’m no expert, I just like to move heavy shit.

What I’ve noticed is that it doesn’t matter the fiber type or fiber count of my bedsheets in getting a good night’s sleep.

It’s the firmness of the mattress that counts.

:wink:

From everything I’ve ever been taught and have read, a sedentary person would not have the same fiber-type distribution as a sprinter. Sprinters are something like 80/20 II/I, while sedentary people are pretty much 50/50. A distance runner would be 20/80 II/I. Olympic weightlifters and powerfliters are both right around 50/50 as well.

Now as STB said, IIx is seldom used unless in situations of extreme stress because they fatigue so easily, so IIx will convert to IIa with training.

Some of this info is a little off. No one is going to know their fiber distribution for sure without biopsy…but it is a pretty firm guess that the guy who can bench press a house and push a truck with ease…but who tires out after about 30 feet of pushing it…is carrying more fast twitch muscle fibers.

I can move a lot of weight but my endurance sucks overall (even though it has improved). If someone grows fast, gets real strong but fatigues easy, you can guess pretty well.

[quote]Professor X wrote:
Some of this info is a little off. No one is going to know their fiber distribution for sure without biopsy…but it is a pretty firm guess that the guy who can bench press a house and push a truck with ease…but who tires out after about 30 feet of pushing it…is carrying more fast twitch muscle fibers.

I can move a lot of weight but my endurance sucks overall (even though it has improved). If someone grows fast, gets real strong but fatigues easy, you can guess pretty well.[/quote]

I agree. I’m basing what I know on studies that include biopsies. One of my professors has also done a lot of work in that area.

If I am understanding correctly, sedentary people have a higher proportion of type2 to type1 but in absolute terms they still have less of both compared to someone who trains?

Otherwise I’m not sure I follow. Why would a sedentary person be better suited to handle a life threatening situation? They don’t train at all, so why would their bodies have adapted type 1 OR type 2s… if anything wouldn’t they be more likely to be doing type 1 tasks during the day than they are to be getting attacked or sprinting?