The Misconception of Lactic Acid as a Fatigue Substance: Is It Actually Beneficial for the Brain?

Is Lactic Acid Really a "Fatigue Substance"? - Introduction

"When you exercise, lactic acid builds up and you get tired" - this has been said for a long time, but recent research and practical experience have shown that this explanation alone is insufficient. We at geefee team were surprised to find that the "refreshed feeling" we experienced immediately after HIIT might be related to lactic acid. This time, we will unravel the role of lactic acid and clearly organize its effects on exercise, fatigue, and the brain.

What is Lactic Acid? Metabolism and the Mechanism of "Transportation" in the Body

First, let's understand what lactic acid is. When muscles break down sugar (glycogen) to produce energy, lactic acid is generated from pyruvate when oxygen supply cannot keep up. This lactic acid is not a "waste product"; it is re-synthesized into glucose in the liver (Cori cycle), and is also used as an energy source by the heart, other muscles that use a lot of oxygen, and even the brain.

The simplistic view of "lactic acid = cause of fatigue" has been re-evaluated over the past few decades, and physiological research has shown that lactic acid plays an important role in circulating and distributing energy throughout the body.

Lactic Acid is Not a Fatigue Substance: The Truth Behind the Misconception and the Actual Mechanism of Fatigue

Why the Misconception Spread

In past experiments, the increase in lactic acid during intense exercise, along with the tingling sensation in muscles and decreased performance, were simplistically linked as cause and effect. However, it is now believed that the burning sensation and immediate fatigue in muscles are mainly influenced by the accumulation of hydrogen ions, leading to a decrease in pH, and changes in ion dynamics (such as potassium).

The "Protective" Role of Lactic Acid

Interestingly, lactic acid has been suggested to contribute to maintaining function during exercise by assisting muscle contraction and preventing excessive potassium leakage from muscle membranes. Therefore, supplements and training theories aimed at forcibly "removing" lactic acid are not necessarily rational. We also tried citric acid as a "lactic acid countermeasure" in the past, but we rarely felt an immediate difference, and we realized again that the basics of recovery are nutrition and rest.

Affecting the Brain and Mood? Lactic Acid's Signaling Action and Noradrenaline

Recent research suggests that lactic acid may affect the brain as a "signaling molecule" more than just a fuel. It is indicated that lactic acid produced during exercise is utilized in the central nervous system and is involved in the release of noradrenaline, a neurotransmitter. Since noradrenaline is deeply involved in arousal, concentration, and mood regulation, it may be related to the experience of feeling "clear-headed" or "refreshed" after short bursts of high-intensity exercise.

However, excessive noradrenaline can also cause insomnia and anxiety, so it is best to avoid intense exercise right before bed. We also avoid late-night HIIT and incorporate it in the morning or during the day.

Exercise Practice and Recovery: HIIT, DOMS Countermeasures, and Dietary Tips

Efficiently Utilizing Lactic Acid with HIIT

HIIT (High-Intensity Interval Training) alternates between anaerobic and aerobic exercise in a short period, allowing for efficient lactic acid production while stimulating both cardiorespiratory function and muscle strength. Effects can be obtained by performing 20-30 seconds of all-out exercise + rest for several sets. However, those with high blood pressure, heart disease, or unaccustomed elderly individuals have risks, so medical confirmation and intensity adjustment are necessary.

Causes and Countermeasures for DOMS (Delayed Onset Muscle Soreness)

Delayed muscle soreness (DOMS) after intense exercise is not caused by lactic acid, but mainly by microscopic muscle fiber damage and the accompanying inflammatory response. Effective countermeasures include:

• Sufficient protein intake and total energy intake before and after exercise
• Moderate caffeine intake (pain reduction and performance improvement have been reported before and after exercise)
• Intake of anti-inflammatory omega-3 fatty acids and polyphenols
• Active recovery (promoting blood flow with light aerobic exercise) and sufficient sleep

Ketogenic and Lactic Acid

Even with low carbohydrate intake, the body performs gluconeogenesis to produce sugar from amino acids, so lactic acid is not completely absent. Lactic acid will be produced during high-intensity exercise, so appropriate recovery nutrition is important even with low carbohydrate intake.

Conclusion

Lactic acid is a multifaceted molecule that cannot be explained by the simple label of "fatigue substance." It is attracting attention as a signal involved in energy supply during exercise, inter-tissue energy transport, and even brain metabolism and neurotransmission. Therefore, instead of trying to forcibly remove lactic acid, a realistic and effective approach is to wisely incorporate HIIT while managing intensity, and support recovery with nutrition and rest. Those with chronic conditions such as heart disease or high blood pressure should consult a doctor about their exercise plan. We will also continue to value our own experiences and apply scientific knowledge to our daily lives.

Disclaimer: The information in this article is for general informational purposes only and does not constitute medical advice. Please consult a qualified healthcare professional before making any health-related decisions.