Lactate Buffering Training: What It Is and How to Improve It

If you’ve ever had your legs completely shut down in a track race — especially in events like the 5,000m or 10,000m — you’ve experienced metabolic acidosis firsthand. Many runners have heard the term “lactate tolerance training,” but few understand exactly why high lactate levels cause performance to collapse.

Importantly, the legs-giving-out sensation during high-intensity effort is a fundamentally different phenomenon from the fatigue that strikes in the final miles of a full marathon. The underlying causes — and the training solutions — are distinct.

In this article, we explain how lactate accumulation drives cells and blood into an acidic state called metabolic acidosis, and how that limits exercise performance. We also cover the physiological mechanisms behind lactate tolerance capacity and the training methods — including beta-alanine supplementation — that improve it.

This article is especially useful for track runners competing in events up to 10,000m who want to understand why their legs fail at race pace and what they can do about it.

Why Does Lactate Accumulation Reduce Running Performance?

When blood lactate rises, body fluids shift toward acidity. This impairs the function of metabolic enzymes, causing a decline in metabolic efficiency and ultimately a drop in energy production and running performance.

Additionally, the hydrogen ions (H⁺) released alongside lactate compete with calcium ions (Ca²⁺) at the sites of muscle contraction, potentially interfering with the contraction process itself.

To understand why lactate accumulates in the first place, it helps to follow the metabolic pathway that produces it.

The body generates energy primarily from carbohydrates, fats, and proteins. As exercise intensity rises, carbohydrate consumption increases disproportionately.

During high-intensity exercise, carbohydrate metabolism accelerates, driving a surge in pyruvate — a key intermediate metabolite. Mitochondria can convert pyruvate into large amounts of ATP, but they become overwhelmed when pyruvate is produced faster than it can be processed. When that happens, excess pyruvate is converted into lactate.

Lactate itself is quickly recycled by mitochondria or released into the bloodstream and converted back to glucose by the liver (gluconeogenesis).

However, when blood lactate rises too high, the simultaneous increase in hydrogen ions (H⁺) causes blood pH to fall toward acidity (※1). This is the root problem for performance.

As blood becomes acidic, the enzymes responsible for carbohydrate, fat, and protein metabolism begin to malfunction. These enzymes operate optimally within a narrow temperature and pH range — even a small deviation sharply reduces their activity.

When lactate accumulation shifts pH toward acidity, enzyme function is inhibited and metabolic efficiency drops. The graph below shows enzyme activity (%) as a function of pH. Notice how dramatically activity falls when pH moves just slightly outside the optimal range of 7.2–7.4.

The process by which lactate accumulation drives blood toward acidity is called metabolic acidosis.

What Is Lactate Tolerance Capacity?

Lactate tolerance capacity can be defined as “the ability to prevent cells and blood from becoming acidic (acidosis) due to lactate production, thereby maintaining stable blood pH.”

That said, blood acidification is not caused solely by lactate production. In a broader sense, lactate tolerance refers to the overall ability to resist any mechanism that pushes blood pH downward during intense exercise.

The sections below cover the non-lactate contributors to blood acidification, as well as the mechanisms by which lactate tolerance capacity improves through training.

Other Causes of Blood Acidosis During High-Intensity Exercise

Beyond lactate production, high-intensity exercise generates hydrogen ions through two additional pathways.

Lactate production was covered above. Here are the other two.

CO₂ and Carbonic Acid Production

Metabolizing carbohydrates, fats, and proteins to produce energy generates CO₂ as a byproduct. CO₂ reacts with water (H₂O) in the body to form carbonic acid (H₂CO₃), which then dissociates to release hydrogen ions (H⁺).

CO2 + H2O ⇔ H+ + HCO3-

The body expels CO₂ through breathing, but as energy demand rises, CO₂ production can outpace exhalation. When excess CO₂ dissolves in water and forms carbonic acid, hydrogen ion levels rise. This respiratory-driven blood acidification is called respiratory acidosis.

ATP Breakdown

When ATP is broken down to fuel muscle contractions, hydrogen ions are released as a direct byproduct.

ATP + H2O → ADP + Pi + H+

This means that ATP breakdown during exercise is itself a direct source of rising hydrogen ion concentration in working muscles.

Why Acid-Base Balance Matters for Race Performance

The evidence is clear: a rapid drop in blood pH during high-intensity exercise directly impairs running performance. That’s why the body has built-in mechanisms to buffer against sudden pH changes.

How Your Body Prevents Rapid Blood pH Drops

The body’s defenses against rapid blood acidification fall into two categories: lactate reuse capacity and buffering capacity.

Lactate Reuse Capacity

This is the body’s ability to take lactate produced during exercise and use it again as an energy source, rather than letting it accumulate in the blood.

Blood lactate rises when fast twitch muscle fibers produce more lactate than they can process locally, causing it to spill into the bloodstream. From there, the lactate is either taken up by slow twitch muscle fibers and burned as fuel, or transported to the liver where it is converted back to glucose via gluconeogenesis.

Two key transporters drive this process: MCT1 (monocarboxylate transporter 1), which draws lactate into muscle fibers, and MCT4 (monocarboxylate transporter 4), which releases lactate from muscle cells into the blood.

MCT1 increases with training across a range of intensities, while MCT4 shows the greatest upregulation specifically with high-intensity training (※2). One study found that 8 weeks of high-intensity training increased MCT1 by 76% and MCT4 by 32%, enhancing the capacity to transport lactate from muscle into circulation (※3).

The rate at which muscle fibers can use lactate depends on mitochondrial volume (number and size) and mitochondrial function. Mitochondrial volume is shaped by total training load, while function is driven primarily by training intensity.

Buffering Capacity

Buffering agents are substances that temporarily resist pH changes when large amounts of lactate are produced and blood begins to acidify.

Within muscle fibers, intracellular buffering agents work first to prevent the cell itself from becoming acidic.

The main intracellular buffering agents are:

Of these, intracellular proteins and carnosine account for the majority of intracellular buffering capacity. Notably, carnosine levels can be increased through beta-alanine supplementation, as demonstrated experimentally (※4). This makes beta-alanine one of the most practical tools for improving lactate tolerance.

Once lactate passes from the cell into the bloodstream, extracellular buffering agents take over.

A detailed breakdown of each extracellular buffering agent is beyond the scope of this article.

How to Improve Lactate Buffering Capacity

To summarize: lactate tolerance capacity is the ability to prevent cells and blood from becoming acidic. Running training improves it through three main mechanisms:

Endurance training improves all three components of lactate tolerance. In particular, enhanced lactate release from fast twitch fibers and improved mitochondrial function occur most prominently with high-intensity training.

Crucially, muscle buffering capacity (βm) shows statistically significant improvement only in groups performing high-intensity training (※5). Moderate aerobic training can improve VO2 max and lactate threshold, but improving buffering capacity requires a high-intensity stimulus (※5).

The research on exactly what intensity threshold triggers these adaptations is still limited. However, given that training at ≥88% VO2 max (≥90% HRmax) is generally classified as high-intensity, regularly incorporating efforts at or above this threshold appears essential for developing lactate tolerance.

Beyond training, beta-alanine supplementation offers a science-backed way to increase muscle carnosine — one of the key intracellular buffering agents — as demonstrated experimentally (※4). Beta-alanine is an internationally recognized ergogenic aid.

Meta-analyses of multiple studies show that beta-alanine is most effective for high-intensity efforts lasting 1–4 minutes (※6, ※7). This means it offers the greatest benefit for 800m, 1,500m, and 10,000m track races.

I personally take beta-alanine. I can’t say for certain whether I feel the effect, but given that it’s an internationally validated ergogenic supplement, I believe the evidence for its efficacy is solid.

References

※1 Robergs RA, Ghiasvand F, Parker D (2004) “Biochemistry of exercise-induced metabolic acidosis.” Am J Physiol Regul Integr Comp Physiol

※2 Pilegaard H et al. (1999) “Effect of high-intensity exercise training on lactate/H+ transport capacity in human skeletal muscle.” Am J Physiol

※3 Juel C et al. (2004) “Effect of high-intensity intermittent training on lactate and H+ release from human skeletal muscle.” Am J Physiol Endocrinol Metab

※4 Artioli GG et al. (2010) “Role of beta-alanine supplementation on muscle carnosine and exercise performance.” Med Sci Sports Exerc

※5 Edge J, Bishop D, Goodman C (2006) “The effects of training intensity on muscle buffer capacity in females.” Eur J Appl Physiol

※6 Saunders B et al. (2017) “β-alanine supplementation to improve exercise capacity and performance: a systematic review and meta-analysis.” Br J Sports Med

※7 Hobson RM et al. (2012) “Effects of β-alanine supplementation on exercise performance: a meta-analysis.” Amino Acids