The term “lactic acid” continues to get used in pretty much all areas of sport, but the term is not accurate. The appropriate term is simply “lactate”. Here is an overview:
Lactate is a byproduct of glycolysis, the process by which your body breaks down glucose for energy. During high-intensity exercise, when energy demands exceed the capacity of the aerobic system, the body ramps up glycolysis to rapidly generate ATP (energy). This produces pyruvate, which is then converted to lactate.
Lactate actually helps you during exercise:
- Acts as a temporary fuel source, especially for the heart, brain, and slow-twitch muscle fibers.
- Helps regenerate NAD⁺ (a receptor of electrons), allowing glycolysis to continue.
- Can be shuttled to other cells or tissues via the lactate shuttle for reuse in aerobic metabolism.
Why “Lactic Acid” Is Not Accurate:
The term “lactic acid” is often used incorrectly to describe the burn or fatigue experienced during intense exercise. However, this is a biochemical misconception:
- Lactic acid doesn’t exist in muscle cells at physiological pH:
- In the human body, at normal pH (~7.4), lactic acid dissociates almost immediately into lactate and a hydrogen ion (H⁺).
- So, what accumulates in muscle is lactate and H⁺, not free lactic acid.
- The “burn” is due to acidosis, not lactate:
- The H⁺ ions**, not lactate itself, contribute to the drop in muscle pH (acidosis), which affects muscle contraction and enzyme function.
- Lactate actually helps buffer some of these hydrogen ions and is not the cause of muscle fatigue.
- Lactate is useful, not harmful:
- Latest research has shown lactate plays a critical role in metabolism, signaling, and even mitochondrial biogenesis.
TL;DR:
- Lactate is a fuel and signaling molecule, not a waste product.
- “Lactic acid” is a misleading and outdated term.
- The discomfort during intense exercise is due to acidosis (H⁺ accumulation, CO2, ammonia, etc.), not lactate buildup.