What is Lactate Threshold and How Can You Improve It?
Yuri Elkaim, BPHE, CK, RHN
Most of the ATP (energy) production used to provide energy during the early stages of exercise come from aerobic sources. However, as exercise intensity increases blood levels of lactic acid begin to rise exponentially. This sudden rise in blood lactate is known as the lactate threshold (or anaerobic threshold).
In untrained people, this appears around 50%-60% of VO2 max (maximum aerobic capacity) while it occurs at higher work rates in aerobically trained individuals (ie. 65% to 80% VO2 max). Basically, what this means is that the fitter you are, the higher the intensity you can sustain before lactic acid is produced.
How and Why is Lactic Acid Produced?
Lactic acid begins to accumulate in the blood when the oxygen demands of the working muscles are not being met. As a result, the body turns to anaerobic metabolism to produce a large amount of ATP (basic unit of energy) very rapidly - with the by-product being lactic acid.
Lactic acid production also occurs because of rising levels of epinephrine and norepinephrine (at around 50%-65% VO2 max) which have been shown to stimulate the rate of glycolytic ATP production and, thus, lactic acid accumulation.
Another explanation for lactic acid accumulation in exercising muscle is related to the enzyme that catalyzes the conversion of pyruvate to lactic acid. This enzyme is lactate dehydrogenase (LDH).
In fast twitch muscle fibers (ones that are recruited during intense, rapid exercise) LDH has a high affinity for attaching to pyruvate, promoting the formation of lactic acid. In contrast, the LDH in slow twitch fibers (ones that are recruited during low intensity exercise) favours the conversion of lactic acid back to pyruvate.
Thus, lactic acid is actually used as a fuel source in slow twitch muscle fibers. That's one of the reasons why performing a proper cool down is important after your runs - it helps shuttle the lactic acid from your fast twitch fibers to your slow twitch fibers for energy use.
A final explanation for the lactate threshold is related to the rate of removal of lactic acid from the blood during exercise. Basically, at exercise intensity increases, your muscles produce lactic acid. At the same time, your body works hard to remove lactate from the blood.
As a result, lactic acid buid up in the blood can arise due to either an increase in lactate production or a decrease in its removal.
So let's sum up the 4 main factors influencing your lactate threshold:
- low muscle oxygen
- accelerated rate of glycolysis
- recruitment of fast twitch fibers
- reduced rate of lactate removal
How Do You Improve Your Lactate Threshold?
To become a faster and more endurant runner you need to be able to run at a faster pace for a longer period of time. In order to accomplish this, you need to train fast. However, in doing so, you may find that your muscles can't last as long because they're producing lactic acid very rapidly compared to running at a slower pace.
Therefore, in order to run faster without the early onset of lactic acid, you need to train at a faster speed for longer duration and continue to do so until your aerobic and anaerobic endurance improve to a point whereby your body becomes more efficient at producing the needed energy.
That's the beauty of interval training. It allows you to run at faster speeds for longer because it chunks your runs into bouts of high and low intensity intervals.
So remember, train slow and you will run slow. Train slow and your anaerobic threshold will be lower than if you trained at faster speeds. Your body adapts to how it is trained. Therefore, push your body to run faster each and every time you train and watch your lactate threshold increase to the point where you'll be running by people who just can't keep up.
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