Lactic Acid (page 1)

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Lactic Acid (page 1)

Lactic acid has been blamed for soreness, injury to muscles, cramps, oxygen debt, etc. Lactic acid really is not so bad. In fact, it may actually be nice in a way, as far as metabolites go. Lactic acid does not cause soreness. A 2004 study found that lactic acid not only does not cause soreness, it may actually counteract fatigue. The study found that the loss of potassium is more likely the cause of fatigue.

We’ve known for at least 15 years that lactic acid has nothing to do with delayed-onset muscle soreness, the kind you feel 24–72 hours after a hard workout session. That soreness is due to a mechanical tearing of myofibrils during eccentric or lengthening contractions. In fact, if during your workout you had someone let the weight down for you on every negative or eccentric contraction so that you do just the positive or concentric reps, you would never get sore. Although concentric contractions do not produce the damage that eccentric contractions do, concentric contractions produce more lactic acid.

Lactic acid is the breakdown product of glucose and glycogen produced during a process called glycolysis. The prefix “glyco” refers to the sugar glucose (which when strung together and stored in muscle makes glycogen); “lysis” means splitting or breakdown. In essence, lactic acid is a glucose molecule cut in half. Glycolysis can proceed so quickly (as when you weight train) that the formation of pyruvate far exceeds the capacity of the mitochondria to accept pyruvate into the Krebs cycle (which ultimately results in the aerobic formation of ATP, the primary form of cell energy). This excess pyruvate is converted to lactic acid. The terms lactic acid and lactate are often used interchangeably, even though they are not the same compound. The lactic acid formed through glycolysis quickly releases a hydrogen ion and forms lactate.

Actively contracting muscles obtain Adenosine Triphosphate (ATP) from glucose stored in the blood stream and the breakdown of glycogen stored in the muscles. Initially, pyruvic acid and small amounts of ATP are generated from the breakdown of glucose. The pyruvic acid mixed with oxygen is converted to carbon dioxide, water and ATP. When muscles contract vigorously for long periods the circulatory system begins to lose ground in the delivery of oxygen. In these conditions, most of the pyruvic acid produced in the breakdown of glucose is converted to lactic acid (LA). As the lactate is produced in the muscles, it leaks out into the blood and is carried around the body. If this condition continues the functioning of the body will become impaired and the muscles will fatigue very quickly. When oxygen becomes available, the lactic acid is converted to pyruvic acid and then into carbon dioxide, water and ATP.

Since a high level of lactate is detrimental to performance, endurance training is used to train the body to perform with a minimal amount of lactate. This may be accomplished by long steady runs, which develop the aerobic capacity by means of capillarisation (formation of more small blood vessels, thus enhancing oxygen transport to the muscles) and by creating greater efficiency in the heart and lungs.With increased aerobic capacity, more oxygen is available to the working muscles and should delay the onset of lactic acid at a given work intensity.

Lactic Threshold

Lactic acid starts to accumulate in the muscles once you start operating above your anaerobic threshold. This is normally somewhere between 85% and 90% of your maximum heart rate (MHR).

If your lactate threshold (LT) is reached at a low exercise intensity, it often means that the "oxidative energy systems" in your muscles are not working very well. If they were performing at a high level they would use oxygen to break lactate down to carbon dioxide and water, preventing lactate from pouring into the blood.

If your LT is low it may mean that:

You are not getting enough oxygen inside your muscle cells.
You do not have adequate concentrations of the enzymes necessary to oxidize pyruvate at high rates.
You do not have enough mitochondria in your muscle cells.
You muscles, heart, and other tissues are not very good at extracting lactate from the blood.

Improving your Lactic Threshold

The aim is to saturate the muscles in lactic acid which will educate the body's buffering mechanism (alkaline) to deal with it more effectively. The following are example running sessions to help improve your LT.

8-200 meter reps at 100% effort. Recovery 4 minutes
4-75 second reps at 100% effort. Recovery 5 minutes
5-60 second reps at 100% effort. Recovery 2½ minutes

A session should be conducted once a week and commence eight weeks before a major competition. This will help the muscle cells retain their alkaline buffering ability.

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