Acid Buildup in the Muscles

Lactic acid, or lactate, is a substance produced in your muscles when you need to move quickly or engage in certain other types of physical exertion. The buildup of this substance triggers pain in active muscles and decreases your chances of causing long-term muscle damage. After muscle exertion ends, your body quickly removes lactic acid from your system.

A woman is exercising in the park.
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Lactic Acid Buildup

When you perform most forms of aerobic exercise, your body fuels your efforts with extra oxygen provided by increases in your breathing and blood flow. However, if you need to sprint, move quickly or lift heavy weights, your body fuels your efforts with glucose, a pure sugar substance derived from carbohydrates in your diet. To gain energy from glucose, your body breaks it down into another substance called pyruvate. Pyruvate is turned into lactic acid, which allows your muscles to continue working for roughly one to three minutes as it quickly builds up.

Lactic Acid Effects

When lactic acid builds up in your muscles, the increased acidity levels trigger a kind of feedback loop that disrupts efficient energy production. In turn, this disruption triggers a burning sensation inside your active muscles. Taken as a whole, this process acts as a natural safeguard for your body by stopping your efforts before you permanently damage your muscle tissue. Once you stop exerting yourself, your muscles go back to producing pyruvate. When you don't require pyruvate to burn glucose, your body uses the substance to help you burn oxygen and recover from your muscular efforts.

Lactic Acidosis

If too much lactic acid builds up in your bloodstream, you can develop a medical condition called lactic acidosis. Symptoms of this disorder include weakness and nausea. In addition to intense physical exertion, potential causes of lactic acidosis include respiratory failure, kidney failure, cancer, HIV/AIDS, use of the diabetes medication called metformin and a blood-borne bacterial disorder called sepsis. Effective treatment of acidosis requires the successful resolution of its underlying cause.


Despite common belief, the buildup of lactic acid in your muscles does not produce post-exercise soreness, according to Dr. Stephen M. Roth, associate professor from the department of kinesiology at the University of Maryland. While lactic acid is typically eliminated from your system within an hour of exercise, muscle soreness usually doesn't peak until one to three days later. Potential causes for soreness after exercise include minute tearing of your muscle tissue and the increased presence of certain chemicals into the tissue associated with your muscles. In turn, these factors can trigger an inflammation and soreness during muscle tissue repair.

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