What blood lactate does in the body of a freediver
Lactate is often, and wrongly, considered ‘metabolic waste’. In fact it helps us with exercise.
- We do not produce lactic acid, we produce lactate. It is produced continuously, even at rest.
- Lactate is not metabolic waste, lactate is used as fuel, both directly and indirectly
- Blood lactate increases rapidly when you hold your breath, even while doing a static.
- The dive reflex promotes anaerobic metabolism. An increase in blood lactate in freedivers indicates that the oxygen supply to the non-essential organs is effectively cut off.
Lactate is formed in tissues as part of lactic anaerobic metabolism. Most people wrongly believe that lactate only forms once the oxygen demand outstrips the supply. As we shall see, the story is a bit more complicated.
At rest and during exercise you produce lactate, and part of that lactate ends up in the bloodstream. As you become increasingly hypoxic, lactate becomes a more important contributor to energy production in muscle cells. At rest only about 50% of the formed lactate is used within the muscle cells. The rest of the lactate moves into the bloodstream.
What blood lactate really tells you
An elevated concentration of blood lactate simply means that you’re exercising. A continuously rising level of blood lactate means you are exercising at an intensity that you can’t keep up for very long. Below a certain level of blood lactate, a steady state exercise can be maintained aerobically. Once you cross the lactate threshold, you will rapidly fatigue and slow down.
The dive reflex and blood lactate
In freedivers, even those performing statics, lactic metabolism increases due to a limited oxygen supply. The limited oxygen supply is the result of vasoconstriction. Interestingly, because of that same vasoconstriction the blood lactate is not transported in the blood stream easily. Lactate in arterial blood increases slowly during a dive and rapidly after vasoconstriction stops and a diver surfaces. If you are well-trained, your body will quickly process the lactate. If not, you are going to have pretty heavy legs after a long diving session.