Acid and Improvements

Let’s review quickly.

At low effort levels, we primarily use fat as a fuel source. As effort increases, the body shifts toward carbohydrates. There is a fundamental and important distinction here. Both are processed in the mitochondria to produce energy.

When fat is used, the primary byproducts are carbon dioxide, water, and energy (ATP). This is a simple and stable chemical process. You can think of these byproducts in practical terms such as breathing and sweat. You exhale carbon dioxide with every breath anyway. So this system, one in which we rely on fat, is not very different from how the body normally operates.

As intensity increases and we rely more on carbohydrates, something changes.

During high energy demand, glycolysis begins to outpace the mitochondria’s ability to process its outputs. When this happens, pyruvate is converted into lactate, often incorrectly referred to as lactic acid.

You have likely experienced this. You are working hard, breathing heavily, and beginning to feel discomfort build.

Many people attribute this sensation to lactate. However, this is a misunderstanding.

The discomfort is not caused by lactate itself. Instead, it is caused by the accumulation of hydrogen ions (H⁺), which increase acidity within the muscle.

At high intensities, your body is producing acid.

Importantly, lactate formation actually helps buffer this acidity by consuming hydrogen ions. You can think of lactate as an exhaust buffer that helps manage the byproducts of high energy turnover. However, as intensity continues to increase, hydrogen ions accumulate faster than they can be cleared.

Simply put:

• Below Zone 2: H⁺ production is approximately equal to clearance, creating a stable system 
• Between Zone 2 and Zone 4: hydrogen ions rise but remain manageable 
• Above Zone 4: hydrogen ion production exceeds buffering, leading to rapid fatigue 

I wanted to establish this distinction before diving deeper into lactate and threshold concepts for one simple reason.

When we prioritize hard work too often, we are quite literally bathing the muscular system in acid.

Training should not simply create fatigue. It should create positive cellular adaptation.

If every day a Soldier came to work and we dripped acid on their skin, we would immediately recognize the problem. It would be investigated and stopped. We intuitively understand that this would be harmful, unsustainable, and counterproductive.

The same principle applies internally.

If, five days a week, we repeatedly impose high levels of intermuscular acidosis, the body cannot adapt fast enough. Instead of improving, it becomes depleted, fatigued, sore, and more susceptible to illness or injury.

Fitness is built at the cellular level. We must develop the body’s ability to convert fuel into energy efficiently, clear metabolic byproducts effectively, and sustain these processes over time.

This is not an argument against intensity. It is an argument for managed intensity.

Training near or around intensities that generate high levels of stress can drive adaptation and improve resilience. However, constantly operating at those levels prevents the body from recovering and adapting properly.

Equally important is training below these intensities. This allows the system to improve its capacity without being limited by excessive acidity and fatigue.

By doing so, we reduce the risk of damage and create an environment where the body can actually adapt and improve.

At this point, a thoughtful reader might ask:

• If the issue is acidity and not lactate itself, why is so much emphasis placed on lactate? 
• If constant high intensity is ineffective, what should the proper balance of training look like? 

Both questions deserve deeper exploration.

For now, here is a simple rule of thumb:

The more intense the workout, the more recovery you need.

• Extremely intense requires about three days of recovery 
• Very intense requires about two days 
• Moderately intense requires about one day 

Any time you train above easy intensity, you must account for recovery. This allows the body to repair, rebuild, and ultimately improve.

Now, let’s return to lactate, this time with a deeper understanding.ts