Pull ups

[dustonian]

Yeah, that's the canon anyway. This Brooks guy and a few other researchers claim lactate itself is used by the mitochondria for oxidative metabolism... but I have yet to find the specified pathway. NADH wouldn't make sense since you have to use an NADH up to create the lactate in the first place from pyruvate. They postulate an intracellular shuttle for the lactate itself--thus killing 2 birds with one stone: more NAD+ for glycolysis, and then lactate DIRECTLY for oxidation. Sounds a bit like a perpetual motion machine to me, but I am still curious to find this supposed reaction spelled out someplace.

EDIT: Found it!... here's an interesting, albeit lengthy review from a non-Brooks related scientist (and perhaps more objective in the sense that he is not trying to build a career of a "novel" pathway?):

http://onlinelibrary.wiley.com/doi/10.1 ... 716.x/full

For those who don't have patience for a rather somnolent review of biochemistry, the final paragraph sums it up nicely:

"Especially during exercise, lactate is nearly completely oxidized. This suggests that lactate is an important fuel for muscular activity. However, at rest, but certainly during exercise, there is usually a net lactate release or at the most no net lactate exchange. This implies that, despite a substantial lactate uptake by the leg, in a net sense lactate does not add carbon for oxidation, in contrast to glucose. For each molecule of lactate that enters the muscle, another leaves the muscle and thus no net flow from lactate to pyruvate and subsequent oxidation occur. Therefore, the role of lactate in muscle is not the provision of energy for muscle contraction like glucose. The role of lactate merely seems to be an intermediate between glucose and glycogen and to their complete oxidation in the mitochondria, that can easily shuttle between the site of production and usage, intra- and extracellular as well as between tissues as implemented by the ‘lactate shuttle’ hypothesis."

This all makes sense now. "Lactate shuttling" and oxidative metabolism in the mitochondria don't actually create any new energy for the muscle cell that it wouldn't get anyway from the well-understood Cori cycle--although it does save a perhaps tedious journey to the liver and back! (Nonetheless it is a novel pathway that doesn't really appear in the textbooks yet and super interesting in an academic regard, especially for the treatment of cancer as described in the article above from the researchers at Duke!) It is really a gross misinterpretation in the popular press to claim that "oxygen doesn't really matter" in terms of aerobic (>2:00) exercise. In short, if there's oxygen available--then the cell will be metabolizing it aerobically. If not, then it will be anaerobic and you're probably about to fall of that route unless you find a good jug soon!

And thanks for the clarification on the Cori cycle Mike. I hate biochemistry.

[mike_a_lafontaine]

I've never heard of lactate directly by the mitochondria, though there could be large volumes of books written about what I don't know. Actually, I think there are large volumes...but...the whole thing seems pointless to have a shuttle for lactate. There already exists a shuttle for pyruvate to get into the mitochondria, so what would be the point of generating the lactate in the cytosol only to send it to the mitochondria? Sure, regenerating the NAD+ to speed up glycolysis for what remains of glucose, but if you have sufficient oxygen to metabolize things in the mitochondria, at that point, glycolytic speed is no longer necessary. It just makes too much sense to send the pyruvate over, use the malate/aspartate shuttle to send equivalents of NADH over, and generate crap-loads of ATP in from them. A quick search of Medline got me nowhere looking for mitochondrially metabolized lactate. Searching ACS journals would likely give similar results. So basically, no proof. Again, that doesn't mean he isn't correct with his theory, afterall, Hans Krebs was a quack...until he proved he was right.

[dustonian]

Right-o. I'm going with that take too.

[One-Fall]

I just had a nerd-gasm.

[tutugirl]

Wow this is great...I couldn't give credit to the person/persons who wrote the article because they had no reference...but it brought up a lot of good stuff so I am glad....which ever it works or doesn't work for you I believe that the hangs work for me. They are quick not a lot of training or hard work since I climb because I love it and in my life that is the only thing that counts.

[dustonian]

Oh, I definitely believe the hangs would work wonders for me, regardless of the fate of all that lactate in my skeletal muscles!!

[One-Fall]

which ever it works or doesn't work for you I believe that the hangs work for me. They are quick not a lot of training or hard work since I climb because I love it and in my life that is the only thing that counts.

2-2, if I could climb like you, I woudnt need to train. Im going to try your workout for a bit.

[JR]

Let us know how it works out One-Fall.

[One-Fall]

Let us know how it works out One-Fall.

Will I tolerate a pump better? - most likely.

Will I climb like Tutu? - most unlikely.

[dustonian]

My lifelong sport climbing goal is to climb as hard as tutu does at 52....