Question: Does Lactic acid have any other effect aart from muscle wise

Mark Burnley answered on 22 Jun 2011:

Great question. We are not even quite sure what effect lactate has on the muscle anyway! In almost certainly DOES NOT cause fatigue (a loss of muscle force during exercise). Because it is really half-broken down sugar, lactate can be used by all cells containing mitochondria as a source of energy. This means every cell in the body except red blood cells can use lactate as a fuel. Lactate can be transported (or “shuttled”) from within a cell, from cell-to-cell, and from tissue-to-tissue. In this way, those cells producing a lot of lactate (fast twitch muscle cells or “myocytes”, for example, release their lactate into the blood stream and allow other more aerobically capable cells to use the lactate for energy (such as slow twitch myocytes or heart cells). Another thing lactate does is cause some nerve cells to fire (“generate action potentials”) and send messages to the brain. This is particularly true of nerve endings in the muscles themselves (called “metaboreceptors”). These nerve cells (neurons) can excite or inhibit other neurons to alter (usually reduce) the amount of muscle activity, slowing you down but preventing fatigue at the same time.

Lastly, there is even experimental evidence that if the muscle has been fatigued in a very specific way (by increasing extracellular potassium), then putting lactate into those cells *increases* muscle force! Under these conditions (which you can’t really get during exercise) lactate is actually increasing performance, not reducing it.

(I keep calling it lactate and not lactic acid, because lactic acid dissociates (sheds a hydrogen ion) at cellular pH (~7), leaving the thing left over to be called “lactate”).