Lactic acid always seems to be athletes’ biggest enemy as it is believed to be the cause of fatigue and muscle soreness.
Lactic acid is rapidly broken down into a compound called lactate, resulting in the release of hydrogen ions. Your body can clear lactate by metabolizing it for energy, but when lactate production exceeds the clearance rate, it accumulates in your muscles and bloodstream.
However, there has never been any experimental evidence proving a cause-and-effect relationship between lactate and fatigue. Although lactate increases when running fast, so do other metabolites, including potassium ions, hydrogen ions, Adenosine diphosphate (ADP), and phosphate, all of which cause fatigue in different ways.
While rising levels of lactate are associated with tired muscles, lactate does not actually cause fatigue. Rather, it is the increased acidity in your tissues, due to the buildup of hydrogen ions, that contributes to the sensation of fatigue.
Lactate also doesn’t cause muscle burning, which may be related to acidosis and the increase in muscle temperature that occurs when you run fast. Burning and aching muscles during an intense workout are caused by lactic acidosis. It happens when the lactate accumulates in your muscles and bloodstream faster than your body can clear it.
Nearly all of the lactate you produce during a workout is cleared within 30 to 60 minutes, even after very intense exercise. Therefore, lactate is long gone by the time you feel sore. Muscle soreness occurs from microscopic tears in the muscle fibers from training and the subsequent inflammation.
Performing an active cool-down after your workout will help clear lactate more quickly than simply resting. Drinking water and staying hydrated also help your body clear excess lactate.