Re:Lactic acid and exercise

[Guest guest]

Though interesting to note that being on a very-low-carb diet inhibits the

muscle soreness that comes after an intense workout. I've definitely experienced

this first hand-- I only get sore muscles after I've eaten grain- or sugar-based

carbs (because the lactic acid is made from glucose).

[Guest guest]

>

> Though interesting to note that being on a very-low-carb diet

inhibits the muscle soreness that comes after an intense workout. I've

definitely experienced this first hand-- I only get sore muscles after

I've eaten grain- or sugar-based carbs (because the lactic acid is

made from glucose).

>

>

>

>

[Guest guest]

Okay, we're wrong about what CAUSES muscle soreness, but you actually just

proved that my reasoning is correct -- that a low-carb diet would inhibit the

cause of muscle soreness, whatever the cause may be. Thanks!

[Guest guest]

I'm an athlete and I notice two distinct types of muscle pain.

1. The burning sensation in active muscle groups during extended

exercise (e.g. mile 20 of a marathon). This often precedes muscle

cramping and the only way to avoid it is to slow down. Conventional

wisdom is that the burning feeling is caused by lactic acid buildup in

the active muscles, which only occurs if you are above your VO2 max

(aerobic capacity). When this happens, your muscles resort to

anaerobic respiration (as a supplement to the ongoing aerobic

respiration of fats and carbs), and anaerobic respiration produces

lactic acid.

2. Muscle soreness that occurs one or more days after heavy exercise.

Stretching and light use of the muscles seems to stop the soreness. I

rarely get this from aerobic exercise, usually only after a

particularly hard weight-lifting session.

They feel quite different to me, but this does not mean they aren't

caused by the same trigger (lactic acid or something else).

The mainstream lactic acid hypothesis makes sense, and I agree with

that that NY Times article doesn't. , that's an interesting

idea about tartaric acid. Do you have any references that explain the

mechanism in more detail?

By the way, , I am a strong believer in low-carbohydrate as the

most important feature of a good diet, but that goes out the window

during extended exercise. The simple truth is fatty acid oxidation

cannot match the energy production rate of carbohydrate oxidation, and

this is why athletes " bonk " if they go too hard for too long without

sufficient carbohydrate intake during the race. Their energy needs

can't be met by fat oxidation alone, and once their liver and muscle

glycogen is used up they have to slow down or stop. Out of gas. I have

personally experienced this many times, as well as the quick recovery

that appropriate carbs (e.g. maltodextrin, glucose polymers) can provide.

Finally, here's an article that appeared last month in the same NY

Times column, " Finding May Solve Riddle of Fatigue in Muscles " , which

implicates leaky calcium channels in muscle cells. The article implies

that the lactic acid hypothesis has been essentially disproven, which

was news to me.

http://www.nytimes.com/2008/02/12/health/research/12musc.html

Tom

[Guest guest]

I agreed with the whole low carb diet being effective for less muscle

soreness.

I meant your reasoning in your statement below...which i believe to be

wrong because you will always have glucose in your blood stream and

that the lactic acid seems to not be the cause of soreness.

" I only get sore muscles after I've eaten grain- or sugar-based

carbs (because the lactic acid is made from glucose). "

Sorry for the confusion...

-

>

> Okay, we're wrong about what CAUSES muscle soreness, but you

actually just proved that my reasoning is correct -- that a low-carb

diet would inhibit the cause of muscle soreness, whatever the cause

may be. Thanks!

>

>

>

>

[Guest guest]

Tom,

> By the way, , I am a strong believer in low-carbohydrate as the

> most important feature of a good diet, but that goes out the window

> during extended exercise. The simple truth is fatty acid oxidation

> cannot match the energy production rate of carbohydrate oxidation, and

> this is why athletes " bonk " if they go too hard for too long without

> sufficient carbohydrate intake during the race. Their energy needs

> can't be met by fat oxidation alone, and once their liver and muscle

> glycogen is used up they have to slow down or stop. Out of gas. I have

> personally experienced this many times, as well as the quick recovery

> that appropriate carbs (e.g. maltodextrin, glucose polymers) can provide.

Why is the rate slower? Is it possible that if certain enzymes were

transcriptionally upregulated over long-term exposure to the diet, and

if there was higher carnitine concentration, etc, this would be

different?

I think, also, that " low-carb " is relative and should be considered

with direct respect to exercise. The harmful effects of carbohydrates

primarily kick in when glycogen stores are full. If they are empty,

or low, it is likely that less carbohydrate will make it through the

first pass through the liver, becuase glycogen synthesis will be

higher, less will be available for de novo fatty acid synthesis, less

will be delivered to the pancreas for insulin secretion, the

postprandial blood sugar spike would be lower, etc. And, ultimately,

you make fat out of the carb you aren't using to make glycogen.

Burning carbs has the added benefit of producing metabolic water and

more carbon dioxide.

Chris

[Guest guest]

> Why is the rate slower? Is it possible that if certain enzymes were

> transcriptionally upregulated over long-term exposure to the diet, and

> if there was higher carnitine concentration, etc, this would be

> different?

Interesting question. My nutrition textbook talks about how fat stores

the most energy by weight, and then says " however, carbohydrate is

more efficient than fat in one very important way: the amount of ATP

produced per unit of oxygen consumed. It takes 6 O2 molecules to

produce 30 to 32 ATP molecules during the aerobic breakdown of a

molecule of glucose (ratio of about 5 ATP to 1 O2), whereas 23 O2

molecules are needed to produce 108 ATP molecules from a 16-carbon

fatty acid (ratio of about 4.5 ATP to 1 O2). Thus, in situations where

an athlete's maximal performance would be limited by the activity of

oxygen-requiring pathways (as in competitive endurance exercise), it

is necessary that muscle cells also use carbohydrate as long as the

carbohydrate supply, especially muscle glycogen, lasts. "

So the limiting factor is oxygen utilization. Thus I don't think

mitochondrial transport via the carnitine transporter is the limiting

factor. I don't know whether the ATP per O2 ratio can be changed much

by conditioning. It's true that for as long as human metabolic

research has been going on, its subjects have been people eating

carb-rich diets, and thus different results may be found in someone

eating and accustomed to a low-carb, fat-rich diet.

One thing I wonder is whether fatty acids with more or fewer carbons

(e.g. MCTs) are more efficiently oxidized than a 16-C FA.

The text does say " the more trained a muscle, the greater its ability

to use fat as a fuel. After a period of aerobic training, muscle cells

contain more and larger mitochondria. " Who knows what the upper limit

is here, and whether fat oxidation can ever provide the same amount of

energy per O2 as carbohydrate oxidation.

> I think, also, that " low-carb " is relative and should be considered

> with direct respect to exercise. The harmful effects of carbohydrates

> primarily kick in when glycogen stores are full. If they are empty,

> or low, it is likely that less carbohydrate will make it through the

> first pass through the liver, becuase glycogen synthesis will be

> higher, less will be available for de novo fatty acid synthesis, less

> will be delivered to the pancreas for insulin secretion, the

> postprandial blood sugar spike would be lower, etc. And, ultimately,

> you make fat out of the carb you aren't using to make glycogen.

I agree with this paragraph entirely. That was essentially what I was

trying to say to .

> Burning carbs has the added benefit of producing metabolic water and

> more carbon dioxide.

But I'm pretty certain that more water is produced from the metabolism

of fats than that of carbs, because fats are more reduced.

Tom

[Guest guest]

Tom,

> Interesting question. My nutrition textbook talks about how fat stores

> the most energy by weight, and then says " however, carbohydrate is

> more efficient than fat in one very important way: the amount of ATP

> produced per unit of oxygen consumed. It takes 6 O2 molecules to

> produce 30 to 32 ATP molecules during the aerobic breakdown of a

> molecule of glucose (ratio of about 5 ATP to 1 O2), whereas 23 O2

> molecules are needed to produce 108 ATP molecules from a 16-carbon

> fatty acid (ratio of about 4.5 ATP to 1 O2). Thus, in situations where

> an athlete's maximal performance would be limited by the activity of

> oxygen-requiring pathways (as in competitive endurance exercise), it

> is necessary that muscle cells also use carbohydrate as long as the

> carbohydrate supply, especially muscle glycogen, lasts. "

Interesting.

> So the limiting factor is oxygen utilization.

Well they posit this, they don't state it as fact. In other words,

they say 'in situations where it is limiting...' Of course it is

sensible that it would be the limiting factor, and maybe this has been

shown elsewhere.

One thing they do not take into account here is that, according to

some evidence cited in the review, " Ketones: Metabolism's Ugly

Duckling, " ketones increase the efficiency of the electron transport

chain. So, while quickly burning nearby fatty acids for energy might

be a little less efficient, burning ketones produced by the liver

might be a little more efficient.

> Thus I don't think

> mitochondrial transport via the carnitine transporter is the limiting

> factor.

Perhaps not, but it sounds like they are making calculations rather

than deriving the statements from experimental evidence about what

limits fat utilization during exercise.

> I don't know whether the ATP per O2 ratio can be changed much

> by conditioning. It's true that for as long as human metabolic

> research has been going on, its subjects have been people eating

> carb-rich diets, and thus different results may be found in someone

> eating and accustomed to a low-carb, fat-rich diet.

Very true. Barry Groves and some others assert that adaptation to a

fat-based diet takes 1-2 years, and after adaptation, physical

performance is superior to on the original carb-based diet.

> One thing I wonder is whether fatty acids with more or fewer carbons

> (e.g. MCTs) are more efficiently oxidized than a 16-C FA.

They are certainly oxidized faster. I don't know if they are oxidized

more efficiently in terms of O2 consumption.

[snip]

> But I'm pretty certain that more water is produced from the metabolism

> of fats than that of carbs, because fats are more reduced.

I'm pretty certain that no metabolic water is produced from fat

metabolism becuse I've calculated it and I can't find any excess of

water, and, moreover, if you look at glucose and a fatty acid, the

limiting constitutent for water production is clearly oxygen, not

hydrogen.

Chris