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Lactic Acid

by David C. LaPorte

Department of Biochemistry
University of Minnesota
Minneapolis, MN 55455

 

1. Lactic Acid: How/why is it formed?

The body has two ways to use glucose: aerobic and anaerobic glycolysis. Aerobic glycolysis is more efficient because electrons which are liberated from glucose are transferred to oxygen. This process produces energy which the cell can trap as ATP. When there isn't enough oxygen, the cell needs some other way to dump these electrons or the system will back up and stop. The cell dumps these electrons into pyruvic acid, a product of glucose, converting it to lactic acid.

What is the necessary role it plays?

Lactic acid is a waste product which results from anaerobic glycolysis. However, the liver can convert it back to glucose by gluconeogenesis.

BTW, the "lactic acid burn" that you get when you go anaerobic is not the result of the high levels of lactate in your blood. Subjects who were given high levels of sodium lactate did not suffer any of the symptoms to being anaerobic. These symptoms result from the drop in pH of the blood which results from dumping acid into it. You'd get the same symptoms from anything that produced acidosis.

Is there a way to recover from build up quickly both through diet and activity?

First, lactic acid clears from the blood and tissues (and pH recovers) very quickly after exercise. Claims such as the need for massage to remove lactic acid hours after a workout are simply wrong. (Massage can certainly be beneficial, but it isn't needed to get rid of lactic acid.)

Second, the reason that lactic acid levels increase dramatically above the so-called anaerobic threshold are uncertain. Two main theories are usually proposed:

Some folks think that lactic acid increases because, as the body no longer has enough oxygen to meet all of its energy needs, lactic acid production goes up. (BTW, even when you've gone anaerobic, you're still processing lots of oxygen. It simply isn't enough to meet all your needs.) According to this theory, lactic acid levels simply reflect the rate of production.

Another theory (which is getting a lot of support) focuses on the rate of lactate consumption rather then production. Lactic acid which is generated in a working muscle is being consumed in other tissues, such as the liver and other muscles. The level of lactic acid in the blood is effected by both the rates of production and consumption. As the working muscle works harder, it produces more lactic acid. This is balanced by the abilities of the other tissues to consume more lactic acid. However, when the rate of production of lactic acid is greater then the fastest rate at which other tissues can consume it, blood lactic acid goes up dramatically.

To understand this better, think of a bucket with a hole in the bottom. You turn on the garden hose and direct the stream into the bucket. The bucket starts to fill with water, but water is leaking out the hole. As the water level goes up, the water leaks out faster. When the leak is running as fast as the hose, the level stabilizes. Increase the flow from the hose a little and the bucket will fill a little more until the leak is now going as fast as the hose again. However, if you increase the flow from the hose too much, the rate of the leak will not be able to match it. The bucket will fill up and overflow.

The flow from the hose is like the production of lactic acid from the working muscle, the level of water in the bucket is like the blood lactic acid level and the leak is like the tissues which are using lactate. When the rate of production of lactate exceeds the rate at which it can be consumed, the blood lactic acid shoots up and you go anaerobic.

As far as what you can do about it, there are some folks who think that general fitness and regular anaerobic exercise can improve the abilities of your nonworking muscles to consume lactic acid.

Sodium bicarbonate buffering has been suggested for people to neutralize lactate (lactic acid) buildup during high intensity weight training. The MAJOR problem is that since it is sodium bicarbonate, taking it will jack up your sodium levels incredibly. One teaspoon is something like twice the daily maximum and effective buffering requires a good bit more. We considered the idea of using Calcium Carbonate, but apparently bicarbonate is effective at a different pH range and CaCO3 would not have the same benefits. And remember, high sodium levels contribute directly to high blood pressure, which is not a good thing when training hard.

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