Lactate, carbon dioxide and metabolism

White muscle fibers are capable of rapid, powerful contractions, but they have poor endurance and negligible aerobic metabolism. They function essentially anaerobically because they contain very few mitochondria, and their contractions produce a lot of lactate. Red muscle fibers, rich in mitochondria and therefore operating more aerobically, use lactate as an energy source if they have enough oxygen.

If lactate concentration in neurons rises above a certain level, they become unable to function properly and neurological disturbances arise. This can manifest, for example, as impaired movement coordination.

When carbon dioxide concentration increases, acidity increases slightly as well — that is, pH decreases — and simultaneously hemoglobin in the blood becomes more willing to release oxygen in the mitochondria for aerobic processes, according to the Bohr effect.

This effect is less significant in white muscle fibers but more pronounced in red ones, which therefore are much better able to burn the lactate produced also by the white fibers. As a result, lactate will inhibit the nervous system’s function later during increasingly intense exercise, or the intensity (for example from the dive start) can be higher, since the muscles take longer to "set in" because they can burn more lactate.

Lactate level and muscle stiffness

I believe the muscle-stiffening problem associated with lactate fundamentally arises because once lactate concentration exceeds a certain level it strongly impairs nervous system function, causing the athlete to freeze up and slow down markedly after about 1–1.5–2 minutes of maximal-intensity exertion; non-athletes will experience this even sooner.

Thinking further, if the body uses lactate more effectively than before, this problem occurs later. The very-high-intensity effort can be extended by a few seconds or intensity can be increased slightly, but in competitive sport this matters a lot. A few seconds' advantage can be the difference to a podium place at a world championship.

Promoting lactate utilization

If we can increase lactate utilization in muscle cells, especially in red muscle cells, neural function will be paralyzed later. Therefore we need to increase lactate oxidation in red muscle fibers so the athlete can sustain intense movement longer. What increases the rate of oxidation in muscles?

• higher temperature,
• increased carbon dioxide concentration,
• decreased pH, acidification,
• increased 1,3-bisphosphoglycerate (BPG) concentration.

Higher temperature can be achieved and maintained by warm-up and muscle work.

Increasing carbon dioxide concentration

There are basically three ways to increase carbon dioxide concentration.

1. Controlled breathing
2. Training mask. You can buy a training mask by clicking here.
3. Mofetta (CO₂ “bath”)

Raising CO2 content sufficiently induces the pH decrease; other solutions should not be tried because excessive acidification inhibits important physiological processes. Exercise itself also causes a pH decrease because lactic acid, lactate and other acidic substances are produced, which in turn also inhibits nerve function. (A higher level of carbon dioxide can also prevent excessive acidification to some degree, since it also functions as a buffer.)

Increasing 1,3-bisphosphoglycerate (BPG) concentration — which happens when a person must adapt over a prolonged period to higher carbon dioxide and/or lower oxygen concentrations (e.g. altitude, pregnancy) — can also be achieved with breathing exercises at near sea level.

To increase carbon dioxide concentration, swimmers, for example, use 5–7–9 breathing sets where hypoxia and hypercapnia (above-average carbon dioxide levels) develop together. The more of this you do, the higher the carbon dioxide concentration in the swimmer’s body becomes, and the more the body adapts to the higher CO2 levels.

The importance of carbon dioxide concentration

Why can’t someone who is an inexperienced swimmer simply swim on a 9-breath pattern if their technique is otherwise good?

Because you have to become capable of it by first swimming a lot on 3-, 5- and 7-breath patterns. This way you can also reach a high carbon dioxide level (and a larger vital capacity, which also reduces the swimmer’s relative weight).

Carbon dioxide concentration can only be increased slowly. The human body is anatomically built so that this can be achieved only slowly, over months. It cannot be done quickly. The respiratory center in the medulla oblongata and the whole body adapt to ever higher CO2 concentrations over a relatively long process. This adaptation brings many benefits to athletes beyond performance improvements (stronger immune system, easier recovery, etc.).

Swimmers, especially good swimmers, have bodies with higher carbon dioxide concentrations. If they did not, they would become "lactated" more easily. After long breaks, results are worse not only because muscle mass has decreased or body weight may have increased, but also because carbon dioxide concentration in the body has decreased due to the absence of 7- and 9-breath swims and their effects.

Besides breath-hold swims, there are other ways to raise CO2 levels in swimmers. Some athletes already use a training mask or, for example in Russia, the Frolov device.

There is an important thing few people know: to raise CO2 levels persistently and substantially, doing 10 minutes of breath-hold swimming three times a week is not enough. You need considerably more such practice.

Recommendations for training

Normally training sessions are structured so that at the end there are cooldown segments where swimmers should swim at moderate speed with relatively infrequent breaths. If I were a swim coach, I would use these segments primarily to increase CO2 levels by having my swimmers use a snorkel whose tube contains an approximately 150–200 ml reservoir. This would increase CO2 concentration in their lungs and throughout the body by the end of training without causing physical suffering or lengthening the training time, while increasing the speed of recovery and improving results, and making ice baths feel better.

For non-swimmers there is the training mask. Applied without choking, it is very effective.

Breathing regulation is easier to change when a person is exposed to moderate or heavy physical exertion. (In such cases the oxygen-hemoglobin saturation curve shifts more to the right.)

Extra-training solutions (e.g. the Frolov device) are useful for preserving or even slightly increasing the gains achieved during hypercapnic periods in training, if someone is very determined. The work itself cannot be avoided; it must be done, only it can perhaps be utilized better.

One final addendum. Changes in the body’s carbon dioxide level can be measured very well with a simple method, by determining the control pause, which requires only a clock. The measurement itself takes a maximum of 1 minute (if more is required, that’s very good!).