Lactic Acid

9/12/2016

Over his Olympic career, Michael Phelps stood on the podium 28 times; 23 of those were for the coveted gold metal.  This is an unprecedented accomplishment. No athlete in modern times can boast such a feat.  It was during the recent summer games in Rio de Janeiro, that I heard an interesting story about this remarkable swimmer.  That is, Michael Phelps has been scientifically proven to produce less than half of the lactic acid of his rivals. Lactic acid? Please explain! Well, when humans exert themselves physically they produce lactic acid. This is the substance that causes fatigue and slows muscle contraction. For most people, it is necessary to have a rest or a recovery period to prepare for another exertion. However, because Michael Phelps produces less lactic acid during heavy exertion, he recovers in just a few minutes, and therefore, he is able to win gold after gold in quick succession.  

Stephen M. Roth, a professor in the department of kinesiology at the University of Maryland, explains the process of lactic acid in the following manner:

As our bodies perform strenuous exercise, we begin to breathe faster as we attempt to shuttle more oxygen to our working muscles. The body prefers to generate most of its energy using aerobic methods; that is, supplying the body with oxygen via breathing. However, under certain circumstances when we may require more oxygen than what we may be capable of generating via breathing, our bodies can produce additional amounts through another method. Such a scenario would be evading a pack of wild dogs or lifting heavy weights. These activities would require a production of energy faster than what our bodies can typically deliver. And oxygen is the main ingredient that our bodies need to make energy. When this happens, our bodies – or more appropriately, our muscles – will generate oxygen anaerobically.  This energy comes from glucose through a process called glycolysis, in which glucose (a simple sugar) is broken down or metabolized into a substance called pyruvate through a series of steps. When the body has plenty of oxygen, pyruvate is shuttled to an aerobic pathway to be further broken down for more energy. But when oxygen is limited, the body temporarily converts pyruvate into a substance called lactate, which allows glucose breakdown–and thus energy production–to continue. The working muscle cells can continue this type of anaerobic energy production at high rates for one to three minutes, during which time lactate can accumulate to high levels.

A side effect of high lactate levels is an increase in the acidity (aka lactic acid) within muscle cells, while disrupting the production of other metabolites. On the surface, it seems counterproductive that a working muscle would produce something that would slow its capacity for more work. In reality, this is a natural defense mechanism for the body; it prevents permanent damage during extreme exertion by slowing the key systems needed to maintain muscle contraction. Once the body slows down, oxygen becomes available and lactate reverts back to pyruvate, allowing continued aerobic metabolism and energy for the body’s recovery from the strenuous event.

Many people erroneously believe that lactic acid buildup causes that soreness we feel in our muscles after we tax them beyond their normal limits. Rather, the production of lactate (and other metabolites) creates the burning sensation often felt in active muscles. However, even to this day, the exact metabolites that are involved in this process remains unclear. This often painful sensation also forces us to stop overworking the body, thus forcing a recovery period in which the body clears the lactate and other metabolites.

While lactic acid levels increase with strenuous exercise, other conditions have been associated with raising the amount of lactic acid in our bodies.  This includes heart failure, or a severe infection (sepsis), as well as trauma or shock. All can lower the flow of blood (and therefore, oxygen) throughout the body. Lactic acid levels can also get elevated when the liver is severely damaged or diseased because the liver normally breaks down lactic acid.

Very high levels of lactic acid cause a serious, sometimes life-threatening condition called lactic acidosis. Lactic acidosis can also occur in a person who takes metformin (Glucophage) to control diabetes when heart or kidney failure or a severe infection is also present.

Other conditions that can cause lactic acidosis are:

• Severe loss of water from the blood (dehydration).
• Blood problems, such as severe anemia or leukemia.
• Liver disease or liver damage that prevents the liver from breaking down lactic acid in the blood.
• Conditions such as severe bleeding, shock, severe infection, heart failure, blockage of blood flow to the intestines, carbon monoxide poisoning, or pulmonary embolism that prevent adequate oxygen from reaching the body’s cells.
• Extremely strenuous exercise or extreme overheating.
• Poisoning by alcohol (ethanol), wood alcohol (methanol), or antifreeze (ethylene glycol).
• Some medicines, such as isoniazid for tuberculosis or metformin (Glucophage) for diabetes (Lactic acidosis is a concern for people who take metformin to control their diabetes, especially if they have poor kidney function).

There are tests available that measure the level of lactic acid made in the body. When the oxygen level in the body is normal, carbohydrates breaks down into water and carbon dioxide. When the oxygen level is low, carbohydrates break down for energy and makes lactic acid.

A lactic acid test is generally performed on a blood sample taken from a vein in the arm but it may also be done on a sample of blood taken from an artery (arterial blood gas). Normal lactic acid is typically within the ranges provided below:

Venous blood: 0.5-2.2 milliequivalents per liter (mEq/L) or 0.5-2.2 millimoles per liter (mmol/L)

Arterial blood: 0.5-1.6 mEq/L or 0.5-1.6 mmol/L

Pleasure in the job puts perfection in the work

Aristotle