SCIENCE TALK: the truth about lactate and lactic acid

Everyone’s favourite subject lactate or lactic acid! The topic that rises up regularly, with plenty of mistakes and misunderstanding. You might have heard athletes, even coaches speak lactate soreness. Even you might have feel lactate after heavy exercise? Did you know that lactate or lactic acid doesn’t cause soreness? Nor fatigue? Not even pain? If not, keep reading…

What is lactate?

Yeah, you read right! Lactate doesn’t cause fatigue, pain or soreness! Lactate and lactic acid are not the same things! Muscles don’t produce lactic acid! If the body produces huge amount of lactic acid, the person will end up a hospital, as it dangerous.

Decades ago scientists found lactic acid, mixed that to lactate, but nowadays, we know that they are a different thing and lactic acid is nothing to do with soreness. So, why people still use this? People believed and still believe that way, so it’s difficult to correct. There’s a lack of understanding.

What happens when you heavy exercises? Heavy exercise breaks down creatine, which forms glucose for energy production. Muscles want more oxygen than they can get during heavy exercise. As they don’t get more oxygen, they accumulate ions. These ions are acidic.

Glucose breaks down to pyruvate to produce energy, but without oxygen, they can’t entry mitochondria (responsible for cellular energy metabolism). So they can’t produce more energy that way, which turn them into lactate. After that, lactate and ions shuttle into the blood and further to the heart for energy (ATP) and liver, where it’s turned back to glucose. So, this means that lactate provides energy, which helps us to continue the exercise.

When you stop exercise, lactate is cleared away within minutes. The soreness which you feel later and the next day is caused by DOMS. Our muscles produce lactate even in low-intensity training. However in a lower amount, so we don’t “feel” it.

What then causes soreness?

Let’s go back to the beginning! When you heavy exercise, you not only produce lactate aka energy. Your ATP hydrolysis increase (release energy) and redox reaction. These again increase H+ (hydrogen), which decrease pH level. And these, in turn, cause acute metabolic acidosis, which might be partly reasons for fatigue and soreness. Metabolic acidosis accumulates of acidic H+ (protons) from ATP hydrolysis and redox reaction. This causes your temporary soreness and fatigue, why want to stop.

what is the Lactate threshold?

Lactate threshold might be confusing and it includes many terms. But basically lactate threshold is that when muscles are metabolically stressed. There is higher lactate accumulation and H+. This lead that stressed mitochondria can’t keep up with lactate clearance. It exports lactate to the blood and blood lactate level rise.

Lactate can be measured by blood on finger or auricle, the most simple ones. Below you can see example results from club runner.

E= easy, S=steady and T=tempo running zones. LT=lactate threshold and LTP=lactate turnpoint.

Midgley, A. W., McNaughton, L. R., & Jones, A. M. (2007). Training to enhance the physiological determinants of long-distance running performance. Sports Medicine37(10), 857-880.

Lactate threshold (LT) also knows as LT turnpoint 1 or aerobic threshold is almost alone fuelled aerobic metabolism. Runners can maintain this pace hours. The pace which you can run your easy runs.

Lactate turnpoint (LTP) also known as LT turnpoint 2, MLSS (maximal lactate steady state), OBLA (onset of blood lactate accumulation), or anaerobic threshold. Dear child has many names, this is what is mean when I said lactate threshold can be confusing. I won’t go deeper what OBLA, MLSS, etc means. Runners can normally maintain this pace about 30-60 minutes. Except during the lactate threshold test, where the pace is increased regularly.

You can improve lactate threshold levels. For instance, tempo and long interval training are an excellent way to improve LTP. The better lactate clearance and tolerance you have the better speed- endurance you will have. In conclusion, next time when you feel soreness or fatigue during exercise you know, it’s nothing to do lactate.

Robergs, R. A., Ghiasvand, F., & Parker, D. (2004). Biochemistry of exercise-induced metabolic acidosis. American Journal of Physiology-Regulatory, Integrative and Comparative Physiology287(3), R502-R516.ISO 690

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