‘Feel the burn from the lactic acid,’ ‘cool down properly so that the lactic acid won’t make you stiff,’ and ‘as long as you stay under your lactate threshold, your body won’t produce lactic acid and it won’t limit your performance.’ These are all commonly used phrases in the sporting world, but there are many facts and myths concerning lactic acid. We investigated a few.
Myth: Lactic acid…
Fact: The term lactic acid is often wrongly used. The correct term to use is lactate, since it does not exist in your body as an acid. The reason for this misconception will become clear further on in this article.
Myth: Lactic acid is produced in your body during high intensity exercise.
Fact: Lactate is one of the products of glycolysis (the process of breaking down glucose to produce energy) and thus is present in your body all the time, even during rest.
Myth: Lactic acid build-up is an indication that the muscles are working anaerobically (in the absence of oxygen).
Fact: The increase in blood lactate levels with increase in exercise intensity is only an indication that more carbohydrates are being used to produce energy. The latest research shows that a muscle might never become anaerobic!
Myth: Lactic acid build-up causes the muscle burn during high intensity exercise.
Fact: Hydrogen ions (H+) are a product of energy production. The higher the exercise intensity, the more H+ is produced, which causes the burning sensation. Without lactate, this burning will become unbearable much sooner during exercise – more on this later.
Myth: Lactic acid build-up causes DOMS (delayed onset of muscle soreness) 24 to 48 hours after a high intensity exercise session.
Fact: Lactate is cleared from your muscles and blood within an hour after exercise. During marathon and ultra-marathon events the intensity is usually not high enough to cause a noticeable increase in lactate concentrations. The soreness is caused by microscopic muscle tears, mainly due to eccentric muscle contraction.
Myth: The lactate threshold is the specific point where the body switches from aerobic (enough oxygen available) to anaerobic (in the absence of oxygen) metabolism and starts producing lactic acid.
Fact: Blood lactate production (and usage) rises continuously as exercise intensity increases. At higher intensities, lactate production overcomes lactate usage, and you start seeing a rise in lactate concentration. This is correctly referred to as the lactate turn point.
The BIGGEST Myth: Lactic acid is a useless, toxic by-product of anaerobic metabolism.
Facts: Lactate is essential for energy production during exercise.
• Lactate produced by the muscles is converted to glucose in the liver, which is an important fuel for the brain and can delay the drop in blood sugar during endurance events.
• Lactate released into the bloodstream can be distributed to glycogen -depleted muscles elsewhere in the body and used to produce energy. The heart also uses lactate for energy production. This phenomenon is known as the “lactate shuttle.”
• As mentioned before, H+ is produced during energy production. Build-up of these ions inside the muscle causes it to acidify, which interferes with muscle contraction and causes the burning sensation during high intensity exercise. Lactate helps to transport H+ out of the muscle cells into the blood stream – from there maybe the misconception that lactate is an acid – and thereby prevents the effects of H+ build-up.
If this is all true, is there than any value in lactate testing and specific training?
A lactate test is conducted by measuring the lactate concentration of a small blood sample at every speed of an incremental running test. These concentrations will rise steadily with each increase in speed and it will be possible to draw a curve indicating the increase in lactate concentration as speed increases. The rise will become more prominent at the speed where lactate production overcomes lactate use/removal. This point is known as the lactate turn point. This has traditionally been used to predict performance and indicate at what specific speed/power output/heart rate the muscles becomes anaerobic. We now know that there is no such thing as an anaerobic threshold and research has shown that these tests cannot accurately predict performance.
The value of lactate threshold testing is twofold:
• It can be used to monitor progression in fitness levels. As an athlete becomes fitter, he will be able to run faster at the same lactate concentration. Thus, if the curve moves to the right, you are on the right track with your training.
• The speed or heart rate at lactate turn point can be used to plan training sessions more effectively. Theoretically, lactate turn point is at about 4 mmol/l (this will be different for every athlete, and it’s therefore a good idea to have it tested).
Some runs should be done at speeds at or just below lactate turn point. These sessions have been shown to improve performance and lower lactate concentrations at a specific speed. Sessions at speeds lower than lactate turn point should be done as base training and recovery sessions, and will improve lactate metabolism (producing energy from lactate). High intensity sessions, at speeds higher than threshold, are important to improve your body’s buffering capacity against the H+ produced in the muscles.
As research becomes more advanced, a lot of what we believe now to be fact will be shown to actually be myth. As athletes, we have to stay in touch with the latest research and use the knowledge to our advantage.