Why does lactic acid cause muscle burn?
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Answer: Lowers pH triggering pain sensors
Acid dissolves muscle fibers — Wrong. Lactate doesn't dissolve muscle. Burning sensation from acidosis (low pH) activating nociceptors (pain receptors) in muscle tissue.
Creates friction during movement — Wrong. No friction involved. Muscle burn from metabolic acidosis—lactate production and H+ accumulation lower pH, triggering pain sensors.
Lowers pH triggering pain sensors ✓ — Correct! Metabolic acidosis! Intense exercise: muscles need ATP fast—glycolysis accelerates (anaerobic metabolism). Glucose → pyruvate → lactate + H+ ions. H+ accumulation lowers pH (acidosis)—activates acid-sensing pain receptors (ASIC channels). That's the burn! Lactate itself isn't the problem—it's actually fuel. H+ ions are the issue. Blood buffers and breathing remove H+ gradually. Elite athletes tolerate acidosis better—training adaptation!