Re: QUERY: Why optimize a marathon runner's fat burning mechanism?

mirror said:

Dan Stumpus said:

This is wildly simple-minded. If you do a brief hard run or time trial
ride, you can use up most of your glycogen in a very short time.

Isn't this fatigue caused by severely crossing your lactate
threshold? Afer all, if I carb load and top off at 2000 calories of
muscle glycogen,

No! You don't have 2000 calories of muscle glycogen (and certainly not local
stores of that). Those "2000 calories" include liver glycogen, and they
*already* carry builtin assumptions that you've taken all necessary steps to
fill your tank.

Quoted message said:

then run five miles all out in noon-time heat, I won't burn 2000 calories
and consequently won't deplete my muscle glycogen.

That's not how it works. You deplete your local stores of muscle glycogen (much
less than 2000 calories) and you don't get all the energy out of those
glycogen stores until you finish processing all the lactic acid that
accumulates (not until after the workout is done)

Cheers,
--
Donovan Rebbechi
http://pegasus.rutgers.edu/~elflord/

mirror said:

Quoted message said:

If you do a brief hard run or time
trial ride, you can use up most of your glycogen in a very short
time.

Isn't this fatigue caused by severely crossing your lactate
threshold? Afer all, if I carb load and top off at 2000 calories of
muscle glycogen, then run five miles all out in noon-time heat, I
won't burn 2000 calories and consequently won't deplete my muscle
glycogen. But I will be fatigued.

Glycogen consumption increases exponentially as you approach maximum output.
I've read that you increase glycogen consumption by a factor of 10 or more
as you go anerobic.

This is why smart hill runners avoid leg burn like the plague -- 5 minutes
of hard burn could use up 50 minutes of aerobic running glycogen.

mirror said:

Donovan Rebbechi said:

Quoted message said:

Isn't this fatigue caused by severely crossing your lactate
threshold? Afer all, if I carb load and top off at 2000 calories of
muscle glycogen,

No! You don't have 2000 calories of muscle glycogen (and certainly not local
stores of that). Those "2000 calories" include liver glycogen, and they
*already* carry builtin assumptions that you've taken all necessary steps to
fill your tank.

Quoted message said:

then run five miles all out in noon-time heat, I won't burn 2000 calories
and consequently won't deplete my muscle glycogen.

That's not how it works. You deplete your local stores of muscle glycogen (much
less than 2000 calories) and you don't get all the energy out of those
glycogen stores until you finish processing all the lactic acid that
accumulates (not until after the workout is done)

Thank you. Do you have a rule of thumb on how much glycogen a given
mass of muscle can store. Or, reversely, how much muscle does it
take to store a gram of glycogen?

No, not really.

Quoted message said:

Also, your concluding remark indicates liver glycogen is
inefficiently consumed in the presence of lactic acid in the blood.

All glycogen is used inefficiently in anaerobic metabolism.

Quoted message said:

Finally, are we talking about the Krebs cycle here, and would
studying a little on the production of adenosine triphosphate give
me the background I need to conceptualize this properly.

Yes. I confess to being somewhat rusty on the details myself.

Cheers,
--
Donovan Rebbechi
http://pegasus.rutgers.edu/~elflord/

Quoted message said:

Finally, are we talking about the Krebs cycle

I had krebs once, itched like hell. Get some RID.

"Dan Stumpus" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

"mirror" <[email hidden]> wrote in

Quoted message said:

What is the reason marathon training programs emphasize
optimizing the fat burning mechanism through long, slow distance?

The argument that such optimization spares glycogen during a race
seems not to hold up. The body stores 2000 to 2500 glycogen
calories, enough to make it to mile 20 or 25.

This is wildly simple-minded. If you do a brief hard run or time trial
ride, you can use up most of your glycogen in a very short time.

Example: My brother is a competitive mtn biker. He told me he had a 5k
time trial coming up, and afterward he and his training partner were doing

a

Quoted message said:

60 mile ride. I advised him against it. He did the trial (uphill at

7500'

Quoted message said:

elevation) in 11 minutes. He massaged his legs, had something to eat,
rested up a bit, then he went out for his road ride, and had *nothing* in
his legs. Where did his mythical 2 hour supply of glycogen go? He ran
through most of it in 11 minutes. He turned around after a few miles.

Just to emphasize this is a more dramatic way, 30 seconds of all out
sprinting can deplete about 1/3 of the muscle glycogen in the vastus
lateralis (outside thigh muscle). Granted, not that we do that very often,
but it does give an idea.

Quoted message said:

On the other end of the scale, if you slow down, you can run well for far
longer than 25 miles. Scott Jurek broke the Western States 100 mile

course

Quoted message said:

record in 15:35, averaging about 9:20 per mile, a time faster than 2:1x
marathoners have been able to manage.

Today I ran a tough 35 mile mountain race, in a bit under 6 hours, average
heart rate 145, temps 90+ at the finish, and still had some zip at the

end.

Quoted message said:

If I'd averaged a heart rate of 150+, I'd have hit the wall, and struggled
in. I passed 10 people in the last 15 miles who were reduced to a

survival

Quoted message said:

shuffle or a walk--because they'd run too fast. We all drank lots of

sports

Quoted message said:

drink and ate during the race.

So, sure, if you run enough miles per week, you can find the magic pace at
which you can run strong for the full 26.2 miles, but the challenge in
marathon training is to raise that pace to it's maximum. And part of that
training is building up your ability to burn fat. 90 minute runs (which
stimulate the creation of more and bigger mitochondria), and longer runs

of

Quoted message said:

3 - 4 hours, where you deplete a lot of your glycogen both stimulate fat
burning . Speed work and Lactate Threshold runs increase the speed you

can

Quoted message said:

run without going anerobic, and improve turnover and efficiency. The more
irons in the fire you have, the faster you'll go.

Quoted message said:

Since the runner is
taking glucose on board through sport drinks at fluid stations,
it seems likely he or she will cross the finish line with a
glycogen reserve.

Eating energy bars and goos will not make you run your marathon that much
faster, especially if you're well trained. Optimal marathon pace in a

well

Quoted message said:

trained runner (80-85% of maximum output) is so hard that you can't digest
much of anything beyond diluted liquids.

Gels properly watered down are very good, maybe not for someone
running 2:08, but how many of us are? I think the research is solid out of
Dave Nieman's lab at Appalachian State that taking in the carbs early in the
race will improve performance. So I would argue it allows one to maintain a
pace so that one covers the distance in a faster time than without.

Quoted message said:

In ultras, which are run at a lower % of maximum output, food is more
important.

Not to mention that one gets burned out on gels and sport drink and
wants something more solid in the gut. (My experience here is limited to a
100 mile mountain bike race--not an ultra).

Quoted message said:

Quoted message said:

In fact, the bonk is glycogen depletion, and most training
manuals contend a runner that hydrates properly (with a sodium-
glucose solution) will not bonk. When they cross the finish line,
the wall will still be ahead of them.

Sheer nonsense. Bonking is almost always caused by bad pacing. You will
always bonk if you run distance X too fast, regardless of what you eat or
drink. Try this experiment. Go out 10% too fast in a marathon. Eat and
drink all the energy food you want. You will still end up shuffling or
walking at the half.

Quoted message said:

Also, competitive marathoners race at paces that demand glycogen
as fuel.

They burn a mix of 30% (or more) fat in addition to glycogen.

Quoted message said:

So, again, what is the value of training slow if the purpose is to
condition the fat burning oxidative mechanism?

]
Because you need both aerobic energy systems (glycogen and fatty acid) to

be

Quoted message said:

highly trained for your best performance. I've read that marathoners get
from 30% to 50% of their energy from fat metabolism. Even my little heart
rate monitor says I generated about 30% of the 4000 calories in my race
today from fat. (so it *must* be true :-)

Quoted message said:

Why not train fast
to compete fast and take glucose on board during the race to use
it as the predominant fuel?

Because that's not the way to run your best, for the above reasons, and a
number of others I'm too fatigued to enumerate. Maybe others will chime

in.

Quoted message said:

Sorry for the harsh tone, must be post-race glycogen depletion...

Dan

Another factor for the slow run (and it is not all that slow IMHO being
60 to 90 sec slower than marathon goal pace) is that plays a role in
building new capillaries so that oxygen and nutrients are closer to every
muscle fiber, increases mitochondria which is where the oxidative processes
for both fat and carbs take place (more little powerhouses at work) and of
course it prepares the body for being out there a long time both mentally
and physically.

"mirror" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Dan Stumpus said:

This is wildly simple-minded. If you do a brief hard run or time trial
ride, you can use up most of your glycogen in a very short time.

Isn't this fatigue caused by severely crossing your lactate
threshold? Afer all, if I carb load and top off at 2000 calories of
muscle glycogen, then run five miles all out in noon-time heat, I
won't burn 2000 calories and consequently won't deplete my muscle
glycogen. But I will be fatigued.

Quoted message said:

Sorry for the harsh tone, must be post-race glycogen depletion...

Thanks for your thoughtful reply. Go get a candy bar. 😉

Fatigue as I see it is the inability to maintain a specific work rate.

Fatigue is caused by a lot of things:

1) energy depletion
2) heat build up
3) too much acidity
4) mental issues (loss of concentration)
5) lack of training
6) dehydration
7) electrolyte issues

Some of these are caused by going out too hard.

It is rare than one gets completely glycogen depleted, the muscle seems to
have some protective capacity to keep some glycogen in reserve since that is
a fuel for its survival. While we may be able to store enough, it is like a
bank that must keep X amount of money in reserve that can never leave the
bank.

"mirror" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

Donovan Rebbechi said:

Quoted message said:

Isn't this fatigue caused by severely crossing your lactate
threshold? Afer all, if I carb load and top off at 2000 calories of
muscle glycogen,

No! You don't have 2000 calories of muscle glycogen (and certainly not

local

Quoted message said:

Quoted message said:

stores of that). Those "2000 calories" include liver glycogen, and they
*already* carry builtin assumptions that you've taken all necessary steps

to

Quoted message said:

Quoted message said:

fill your tank.

Quoted message said:

then run five miles all out in noon-time heat, I won't burn 2000

calories

Quoted message said:

Quoted message said:

Quoted message said:

and consequently won't deplete my muscle glycogen.

That's not how it works. You deplete your local stores of muscle glycogen

(much

Quoted message said:

Quoted message said:

less than 2000 calories) and you don't get all the energy out of those
glycogen stores until you finish processing all the lactic acid that
accumulates (not until after the workout is done)

Thank you. Do you have a rule of thumb on how much glycogen a given
mass of muscle can store. Or, reversely, how much muscle does it
take to store a gram of glycogen?

Also, your concluding remark indicates liver glycogen is
inefficiently consumed in the presence of lactic acid in the blood.
Is this what you are telling me?

The primary function of liver glycogen is a fuel source for the brain.
The liver in a male can store about 100g of glycogen.

Quoted message said:

Finally, are we talking about the Krebs cycle here, and would
studying a little on the production of adenosine triphosphate give
me the background I need to conceptualize this properly.

Only if you really feel the need. To some extent you are going to be
looking at each tree in a forest and miss the grandeur of the forest.

Training for a marathon (or any distance event that is primarily aerobic
starting with the 800m) requires a multi paced approach. There are long
runs to build aerobic capacity; there are "tempo" runs at about lactate
threshold pace to build "sustainable speed"; there are VO2max efforts to
optimize that system and provided "miler's speed" as I like to call it;
there are strides to build leg speed without the metabolic problems
associated with other training; there might be the need to develop anaerobic
capacity for the 800/1500 runner (not much need for this in a marathoner).

Each training is important in developing the whole athlete. Knowledge of
what is going on at the cellular level can get one way too confused to be
honest since all energy systems are always in use. The intensity (relative
to VO2max) determines the contribution of each. Rather than thinking of
turning energy systems on and off, think of energy systems as being on a
dimmer switch system. At times one dimmer light will be providing more
light than another one, but the second and third lights are always on.

Quoted message said:

Thanks again.

"Dan Stumpus" <[email hidden]> wrote in message
news:[email hidden]...

Quoted message said:

mirror said:

Quoted message said:

If you do a brief hard run or time
trial ride, you can use up most of your glycogen in a very short
time.

Isn't this fatigue caused by severely crossing your lactate
threshold? Afer all, if I carb load and top off at 2000 calories of
muscle glycogen, then run five miles all out in noon-time heat, I
won't burn 2000 calories and consequently won't deplete my muscle
glycogen. But I will be fatigued.

Glycogen consumption increases exponentially as you approach maximum

output.

Quoted message said:

I've read that you increase glycogen consumption by a factor of 10 or more
as you go anerobic.

This is why smart hill runners avoid leg burn like the plague -- 5

minutes

Quoted message said:

of hard burn could use up 50 minutes of aerobic running glycogen.

The rate of glycogen use above LT can be as high as 19x the rate below LT.

As I noted in another post, 30 sec of all out sprinting will burn through
~1/3 of the muscle glycogen in the vastus lateralis.

Dan Stumpus said:

"mirror" <[email hidden]> wrote in

Quoted message said:

What is the reason marathon training programs emphasize
optimizing the fat burning mechanism through long, slow distance?

The argument that such optimization spares glycogen during a race
seems not to hold up. The body stores 2000 to 2500 glycogen
calories, enough to make it to mile 20 or 25.

This is wildly simple-minded. If you do a brief hard run or time trial
ride, you can use up most of your glycogen in a very short time.

Example: My brother is a competitive mtn biker. He told me he had a 5k
time trial coming up, and afterward he and his training partner were doing a
60 mile ride. I advised him against it. He did the trial (uphill at 7500'
elevation) in 11 minutes. He massaged his legs, had something to eat,
rested up a bit, then he went out for his road ride, and had *nothing* in
his legs. Where did his mythical 2 hour supply of glycogen go? He ran
through most of it in 11 minutes. He turned around after a few miles.

Talk about wildly simple minded.

Ever occur to you that there are many other sources of muscular fatigue
than glycogen depletion and those might have contributed to his performance?

Lyle

Dan Stumpus said:

"mirror" <[email hidden]> wrote in

Quoted message said:

What is the reason marathon training programs emphasize
optimizing the fat burning mechanism through long, slow distance?

The argument that such optimization spares glycogen during a race
seems not to hold up. The body stores 2000 to 2500 glycogen
calories, enough to make it to mile 20 or 25.

This is wildly simple-minded. If you do a brief hard run or time trial
ride, you can use up most of your glycogen in a very short time.

Example: My brother is a competitive mtn biker. He told me he had a 5k
time trial coming up, and afterward he and his training partner were doing a
60 mile ride. I advised him against it. He did the trial (uphill at 7500'
elevation) in 11 minutes. He massaged his legs, had something to eat,
rested up a bit, then he went out for his road ride, and had *nothing* in
his legs. Where did his mythical 2 hour supply of glycogen go? He ran
through most of it in 11 minutes. He turned around after a few miles.

Talk about wildly simple minded.

Ever occur to you that there are many other sources of muscular fatigue
than glycogen depletion and those might have contributed to his performance?

Lyle

Donovan Rebbechi said:

mirror said:

Donovan Rebbechi said:

>Isn't this fatigue caused by severely crossing your lactate
>threshold? Afer all, if I carb load and top off at 2000 calories of
>muscle glycogen,

No! You don't have 2000 calories of muscle glycogen (and certainly not local
stores of that). Those "2000 calories" include liver glycogen, and they
*already* carry builtin assumptions that you've taken all necessary steps to
fill your tank.

>then run five miles all out in noon-time heat, I won't burn 2000 calories
>and consequently won't deplete my muscle glycogen.

That's not how it works. You deplete your local stores of muscle glycogen (much
less than 2000 calories) and you don't get all the energy out of those
glycogen stores until you finish processing all the lactic acid that
accumulates (not until after the workout is done)

Thank you. Do you have a rule of thumb on how much glycogen a given
mass of muscle can store. Or, reversely, how much muscle does it
take to store a gram of glycogen?

No, not really.

Average diet, maybe 3-4 g glycogen/lb lean body mass is stored.

With proper carb loading, you can double this to 6-8 g/lb LBM (12-16
g/kg). Add another 50-100 grams for liver glycogen.

thereabouts anyhow.

Lyle