"draining fluid from your legs"

[aicabsolut]

Exactly. It is fuel.

http://www.cyclingnews.com/fitness.p...ctic_frederick

[OakLeaf]

Wait, so LT training is a myth, too??? I understand how lactic acid is re-converted into fuel, but I thought there was still a consensus that the lactate threshold is real and not limited to "going superfast up supermountains" (for one thing, that characterization is an externalized one that suggests that different people don't have different levels of aerobic conditioning and only the most highly conditioned athletes can approach their LT)?

I don't really have the biochem background to completely understand this stuff, but I've been following the news stories with interest. Last I did any searches on delayed-onset muscle soreness (a year or two ago) there really wasn't a consensus about what causes it. Sure, it makes sense that overloading the muscles in eccentric contraction would create micro-tears, which would in turn cause soreness and eventual hypertrophy. But I'm not sure how repetitive motion under a light load would tear a muscle, or why doing it for four hours would tear it any more or less than doing it for one hour. (in the same way that it doesn't create microfractures in a bone - you can cycle all day and not increase your bone density, e.g., and you can spin all day and increase your muscle tone but not muscle size)

(and by "spinning" I mean the common meaning not the trademarked one - i.e. high RPM low load)

[aicabsolut]

I don't think that's what the article was saying.

Lactate is: 1) a valuable energy source within working muscle, non-working muscle, and the heart, 2) quantitatively the most important contributor to the making of glucose in the liver, and 3) subject to training- induced improvements in its use as a fuel.

I think LT training is important because there would be a point at which you are no longer efficiently using it as fuel.

The ability to use lactate as fuel, particularly within the muscle itself, varies with the trained characteristics of aerobic muscle fibers, specifically via endurance training[5].

So I think LT training is a separate animal from saying that too much lactic acid leads to soreness. The way I understand it is that soreness is related to the amount of stress put on the muscles and hydration and recovery.

[cyclechick2008]

I think that for me to work on my Lactic acid threshhold I could conceivably get to or over my MHR. So much cycling training is done at 70% MHR. This is a range for most people where they build up their efficiency of aerobic exercise. that's why it is important to do the build a base workouts when you start. It helps the mitochondria become more efficient at their job.

I know in running, Lactic Threshold is a different animal or so I"m told by some runner friends.

Kim

[Zen]

that's why it is important to do the build a base workouts when you start. It helps the mitochondria become more efficient at their job.

As far as I know (which isn't very far) lactose fermentation involves the number of mitochondria (mitochondrial mass) increasing with training, not an individual mitochondria becoming more efficient.

[alpinerabbit]

I did some research on pubmed regarding what "base building" does to you. There's much more going on, like import proteins rising in muscle cells / mitochondria,and the liver producing more apolipoprotein (carrier protein for fatty acids) etc, etc.

I am confused about lactate being used as fuel.
I was taught lactic acid is not very efficient as fuel in the muscle during exercise. The way I read the abstract (quoted below) is that some is used as fuel, but also lactate is only removed within the cells during recovery, when they have plenty of oxygen - but this does not produce a lot of energy compared to glycolysis (aerobic metabolism produces 19x more energy than anaerobic per mole of glucose).
There is a cycle in the liver to convert lactate back to glucose (which, however, requires energy).

Brooks GA. The lactate shuttle during exercise and recovery. Med Sci Sports Exerc. 1986 Jun;18(3):360-8. Review
Most (75%+) of the lactate formed during sustained, steady-rate exercise is removed by oxidation during exercise, and only a minor fraction (approximately 20%) is converted to glucose. Significant lactate extraction occurs during net lactate release from active skeletal muscle; the total lactate extraction approximates half the net chemical release. Of the lactate which appears in blood, most of this will be removed and combusted by oxidative (muscle) fibers in the active bed and the heart. The "shuttling" of oxidizable substrate in the form of lactate from areas of high glycogenolytic rate to areas of high cellular respiration through the interstitium and vasculature appears to represent an important means by which substrate is distributed, metabolic "waste" is removed, and the functions of various tissues are coordinated during exercise. During recovery from sustained exhausting exercise, most of the lactate accumulated during exercise will continue to be removed by direct oxidation. However, as the muscle respiratory rate declines in recovery, lactate becomes the preferred substrate for hepatic gluconeogenesis. Practically all of the newly formed liver glucose will be released into the circulation to serve as a precursor for cardiac and skeletal muscle glycogen repletion. Liver glycogen depots will not be restored, and muscle glycogen will not be completely restored until refeeding. This is because the diversion of lactate carbon to oxidation during exercise and recovery represents an irreversible loss of gluconeogenic precursor and because the processes of protein proteolysis and gluconeogenesis from amino acids are insufficient to achieve complete glycogen restitution after exhausting exercise

[Zen]

Can you repeat the question?

I'm gonna have to read that one about five more times, at least.
Was 1986 the latest data you could find? That's kind of old.