What changes do occur in blood lactic acid concentration before, during and after a vigorous activity?

Before a vigorous activity, blood lactic acid concentration is typically low as the body is in a resting state and not producing high levels of lactic acid.

During a vigorous activity, blood lactic acid concentration increases as the muscles are working hard and producing lactic acid as a byproduct of anaerobic metabolism. This increase in lactic acid can lead to muscle fatigue and a burning sensation in the muscles.

After a vigorous activity, blood lactic acid concentration will gradually decrease as the body works to clear the lactic acid from the muscles and bloodstream. This process is known as the "lactic acid clearance" and can be aided by light exercise, stretching, and proper hydration. It is important to allow the body time to recover and remove the excess lactic acid to prevent muscle soreness and fatigue.