Do you feel some pain in your leg after a long run? Or perhaps a dull ache on your calves after working out at CKO Kickboxing? This burning sensation is often attributed to lactic acid buildup. Lactic acid is a compound that play a key role in metabolism and it’s especially active during intense exercise. But the question you probably need to ask is, does lactic acid trigger muscle fatigue and pain?
The simple answer is no.
For many years, runners and athletes have attributed muscle fatigue and pain to lactic acidosis, a condition in which there is an excessive amount of lactic acid in your muscle due to low oxygen during intense exercise.
But scientists have found that because our blood pH level is high, lactic acid does not exist in your body. Rather, the lactic acid molecule is divided into two parts during metabolic processes, lactate and proton.
Lactic acid vs. Lactate
Although many of us may use the terms lactate and lactic acid interchangeably, they’re not one and the same. Lactate is the byproduct of exercise, while lactic acid which is made up of positive hydrogen ion and negative lactate ion, divides into lactate ion and hydrogen ion when dissolved in water.
Lactate is produced when glycolysis becomes anaerobic, as an end product of the breakdown of glucose. Without delving deeper into biochemistry, glycolysis is the process by which your body fuels the muscles – by breaking down glucose and producing adenosine triphosphate (ATP). ATP is basically the fuel that your muscles feed upon.
But here’s the thing – the amount of ATP that gets produced varies on how much oxygen is available during glycolysis. So when you workout at high intensity, your muscles don’t get sufficient oxygen. There’s low oxygen but high demand for ATP. As a result, glycolysis becomes anaerobic and this triggers the body to produce lactate.
But what causes muscle fatigue and pain after exercise?
Lactate, not lactic acid, is the byproduct of anaerobic glycolysis. It’s a biomarker of glucose breakdown and fatigue, but it’s not the cause of the said fatigue. In fact, lactate holds a key role in cellular processes – the heart and brain uses it as an energy source.
So it’s not the culprit.
Instead, the cause of the burn is the circulating hydrogen ions which create an environment that is acidic in your muscle. The delayed onset muscle soreness (DOMS) which runners, bodybuilders and athletes experience following an intense workout remains a complicated topic. The most accepted theory is that it is a result of a combination of inflammation and micro damage to the fibers in your muscle.
Understanding the Lactate Threshold
The lactate threshold is essentially the limit at which the body becomes unable to clear lactate at the speed it’s producing. Lactate starts to build up in your blood due to an increased lactate production or perhaps a reduced lactate clearance.
Lactate levels go up during exercise and lactate is recycled to fuel cells and allow for different bodily processes to take place. Oxygen is needed in order to metabolize lactate but during high intensity exercise, the aerobic system is unable to handle the oxygen requirement hence the accumulation of lactate in the blood.
When your body reaches the lactate threshold, it begins to produce more lactate and more hydrogen ions are released, which leads to a more acidic environment in the cellular level, causing the burn.
To counter this, you need to rest and make sure your body gets enough oxygen to return to normal. You can also watch this video to find out how you can increase lactate threshold: