What exactly is bicarbonate?

Bicarbonate is not a foreign substance in our bodies; rather, it is a natural component of our blood and part of the most important buffer system outside the cells. For us athletes, this mechanism becomes particularly relevant when the intensity increases and our muscles need to provide a lot of energy in a short amount of time.

But how exactly does this buffer work? And why can additional bicarbonate help support our performance during certain types of exercise?

Bicarbonate, chemically HCO₃⁻, is a negatively charged particle that circulates in our blood. Together with other buffer systems, it helps the body maintain the blood’s pH within a narrow range around 7.4. At rest, the bicarbonate concentration in the blood is typically about 24 mmol/L.

This regulation is crucial. Even small changes in pH can affect numerous processes, including enzyme activity, energy production, and muscle contraction. The Australian Institute of Sport therefore describes bicarbonate as a key component of the body’s pH buffer system.

It is important to distinguish between bicarbonate and sodium bicarbonate. Bicarbonate is the buffer molecule in our bodies, whereas sodium bicarbonate is a compound of sodium and bicarbonate, and we can use it to absorb additional bicarbonate.

What happens during high-intensity exercise?

During high-intensity intervals, climbs, time trials, or when increasing pace, the muscles’ energy demand rises very quickly. A larger proportion of the required energy is then supplied through rapid glycolysis. Glycolysis describes the process by which our cells directly extract energy from glucose; this process occurs without oxygen, i.e., anaerobically.

As exercise intensity increases, hydrogen ions (H⁺) are produced and accumulate faster than they can be buffered and removed. This causes the pH level within the muscle cell to drop. This altered environment can impair energy production and muscle contraction, thereby contributing to fatigue.

It is important to make a distinction here: Lactate is produced in parallel during intense exercise, but it is not simply the substance that causes so-called “acidosis.” Hydrogen ions are primarily responsible for the buffering effect of bicarbonate. Nevertheless, fatigue remains a complex process and cannot be reduced to a single substance or mechanism.

How does the bicarbonate buffer work?

Some of the hydrogen ions are transported from the muscle cell into the blood. There, bicarbonate acts as an extracellular buffer.

Bicarbonate combines with the hydrogen ions. Through a series of reaction steps, this produces water and carbon dioxide. The carbon dioxide is transported to the lungs and exhaled.

In simple terms:

H⁺ + HCO₃⁻ → H₂O + CO₂

A higher concentration of bicarbonate in the blood can increase the gradient between the muscle and the blood, making it easier for hydrogen ions to be transported out of the muscle cells and buffered outside the cells. This can help maintain the conditions necessary for high-intensity muscle contraction for a longer period of time.

Bicarbonate does not prevent fatigue. However, it can influence one of the factors that limit our performance during intense exercise.

Why is sodium bicarbonate taken as a supplement?

Taking sodium bicarbonate can temporarily increase the bicarbonate concentration in the blood. This process is often referred to as bicarbonate loading.

In scientific studies, doses of 0.2 to 0.4 grams of sodium bicarbonate per kilogram of body weight are typically used. Depending on the dose and the individual’s response, the bicarbonate concentration in the blood can increase by about 5–6 mmol/L. This temporarily provides the body with greater extracellular buffer capacity.

The Australian Institute of Sport classifies sodium bicarbonate as Group A. This category includes supplements for which there is strong scientific evidence supporting their use in specific sports applications.

Conclusion

Bicarbonate is a natural component of our blood and a central part of the body’s acid-base buffer system. During high-intensity exercise, it helps remove and buffer hydrogen ions that accumulate in and around the working muscles.

Therefore, supplementing with sodium bicarbonate can increase the blood’s buffering capacity and support our performance during certain high-intensity activities.

However, the effect depends on the exercise profile, dosage, timing, and our individual response. We’ve written another blog post on this topic; here you can read about how bicarbonate can be used and when it might be beneficial.

 

Bicarbonate is therefore not a shortcut to better performance. It is a tool that can be used strategically, building on a well-functioning fueling strategy, and must be carefully tested during training.