There is a common misconception amongst athletes and the general population that the muscle soreness experienced in the 24-72 hour period after unaccustomed, new or vigorous exercise – known as delayed onset muscle soreness (DOMS) – is caused by a build up of “lactic acid in the legs”.  Although the causes of DOMS are not fully understood, we can say with certainty that it has little to do with lactic acid.  This week we delve a little into exercise physiology and attempt to dispel this myth.

Lactate is a by-product of anaerobic metabolism.  As we exercise we use our principle energy source glucose.  The metabolism of glucose, in the absence of sufficient oxygen, leads to the build up of lactate within our bloodstream.  However, this build up of lactate quickly reduces and returns to normal levels on ceasing exercise as we breathe in enough oxygen to neutralise the build up during the strenuous workout. 

This is my last lactate profile, showing a speedy return to resting blood lactate levels within forty minutes of ceasing a bout of intense exercise to exhaustion.

We can see that blood lactate levels peak during intense exercise but return to normal relatively quickly once we stop exercising.  Elevated blood lactate levels are responsible therefore for “burning” feeling in the muscles during exercise but cannot be contributory in the case of DOMS, which tends to peak at 24-72 hours after strenuous exercise.  Lactic acid certainly causes the pain in the legs in the last 100m of a 400m run but has little to do with the pain experienced walking down the stairs two days later.

DOMS is caused by unaccustomed, new or higher intensity exercise, particularly eccentric exercise.  It’s attributed to micro trauma within the muscle and cannot be cured.  So if you’re suffering with it rejoice in the fact that it’s testament to your hard work, know that it has nothing to do with lactic acid and console yourself in the knowledge that it rarely lasts longer than 4-5days!