Lactic acid

[alpinerabbit]

Firstly, our bodies don't produce lactic acid but instead produces lactate, a very important form of energy. The lactic acid production was widely believed to be true for over 60+ years but as we've learned more about how the body works this has been debunked.
What occurs in our body and exertion increases is we begin to rely more heavily upon the lactate created in our bodies. The lactate itself is broken into glucose which is used by the bodies under strenuous activity.

http://www.time-to-run.com/theabc/lactic.htm
Another misconception is that lactate is responsible for acidifying the blood, thereby causing fatigue. To the contrary, lactate is actually an important fuel that is used by the muscles during prolonged exercise.

I am not really sure if you as well as the webpage quoted are trying to be funny or not.

Lactate is nothing else than the deproteinated form of Lactic acid. I am not biochemist enough to know exactly what metabolic cycles myocytes go into if high energy demand is not matched by oxygen delivery (or how knowledge has changed since I toiled through the textbooks), so I will leave that open to debate. The fact remains that during strenuous exercise, lactate concentrations rise measurably, with a concurrent loss in performance but to say that the first causes the second would be a post hoc argument since I am not the specialist.

Lactate is a molecule with 3 carbon atoms and cannot be broken down into glucose, which has 6 C atoms.
The liver can turn lactate into glucose again but the cori cycle actually consumes energy.
http://web.indstate.edu/thcme/mwking...eogenesis.html

The debunking mentioned in your third link probably alludes to the theory that stiff/sore muscles do not come from lactate, but are these days thought to come from microlesions in the myocytes (muscle cells).

What causes decreased athletic performance is the production of protons caused by the breakdown of ATP by the muscles during exercise. This production of protons is kept in check until we meet a threshold (normally called lactate threshold) where our oxygen demands outstrip supply. This begins a buildup of these protons in our muscles which increases acidity (acidosis)

from the dissociation of the lactic acid produced into lactate and protons; ATP is continuously recycled. The stash of ATP in the cells is limited.

When your legs get to the stage of where they feel like they weigh a few ton each this may be caused by two things. It *could* be acidosis. However it's more likely that your glucogen stores have been depleted and that you need glucose.

Indeed, the powerless feeling seems to me from personal experience to come from simple lack of fuel, while the burning will go away with a bit of rest.


Sorry to be a know-it-all, being a considerable noob to the realm of cycling, but I do have a degree in biology. Textbook knowledge admittedly, when it comes to biochemistry.


Dunno about your toes there, Brandi - my feet hurt from being restricted in tight cycling shoes or hiking boots.