Why We Feel the Burn: The Science of Lactic Acid
With Why We Feel the Burn: The Science of Lactic Acid, an all-or-nothing answer misses the point. The practical answer is more specific.
Fitness advice becomes useful when it can be applied consistently. The best option is usually the one that fits the goal, equipment, experience, and recovery available. The practical question is how to use the information without overstating it.
What Is Lactic Acid?
Lactic acid is a byproduct that’s produced during exercise when your body breaks down glucose for energy within muscle cells. When you’re working out, your body uses a process called anaerobic glycolysis to produce energy.
While this process allows you to keep working out at a high intensity, the accumulation of lactic acid in your muscles can lead to the burning sensation you’re familiar with.
The Role of Lactic Acid in the Body
Lactic acid isn’t just a byproduct of exercise; it’s a useful component of the human body’s overall function. Beyond its role in workouts, lactic acid plays an important part in cell respiration, helping cells convert glucose into energy.
Beyond that, lactic acid is involved in glucose production and molecule signaling, which are critical for the proper functioning of cells, tissues, and organs. It acts as a key player in ensuring that our body systems operate smoothly.
The Role of Glucose in Exercise
When you exercise, your muscles need a quick supply of energy to contract and keep moving. Normally, your body prefers to use oxygen to break down glucose, which comes from the carbohydrates in your diet.
However, when you're performing strenuous exercise, your muscles' demand for oxygen exceeds the supply available. In these moments, your body shifts from aerobic (with oxygen) metabolism to anaerobic (without oxygen) metabolism.
Why Do We Feel the Burn?
The burning sensation you feel during exercise is the result of lactic acid building during intense workouts. As your muscles rely more on anaerobic metabolism, the level of lactic acid increases faster than your body can clear it.
Lactic acid buildup can slow down your ability to keep going by making muscle contractions less efficient. This is why, when you reach a certain intensity, you may feel that your muscles are “giving out” or struggling to continue.
Is Lactic Acid a Bad Thing?
Many people assume lactic acid is harmful, but neither lactic acid causes muscle soreness nor the burning sensations experienced during intense exercise. In fact, lactic acid is a necessary part of your body’s response to strenuous exercise.
The Burn: Intensity and Oxygen Deprivation
The intensity of the workout largely determines how quickly lactic acid builds up in your muscles. During high-intensity activities such as sprinting or weightlifting, your muscles require energy faster than your body can supply oxygen.
In other words, the burn is a direct signal that your muscles are working harder than they would under normal conditions. They need more oxygen and energy than your body can supply in that moment, leading to the accumulation of lactic acid and the accompanying sensation.
Lactate vs Lactic Acid: What’s the Difference?
While the terms lactate and lactic acid are often used interchangeably, they are not the same. Lactic acid forms when lactate combines with a hydrogen ion.
On the other hand, lactate itself is a valuable energy source. It gets recycled back into the system, helping to fuel your muscles during prolonged physical activity.
The Connection Between Lactic Acid and Muscle Soreness
Contrary to popular belief, lactic acid isn’t the primary cause of muscle soreness. The soreness you feel 24 to 48 hours after a workout—known as delayed onset muscle soreness (DOMS) —is caused by tiny tears in the muscle fibers, which occur when you perform unfamiliar or intense exercises.
However, lactic acid can still contribute to the immediate feeling of fatigue and weakness in your muscles during and shortly after intense exercise. This is due to lactic acidosis, which occurs when lactic acid production exceeds clearance, leading to symptoms such as muscle pain and fatigue.
How to Reduce Lactic Acid Build-Up
While you can’t avoid lactic acid buildup entirely during high-intensity exercise, there are several strategies you can use to help your body become more efficient at handling it and getting rid of lactic acid by promoting its natural ability to process and clear it.
- Take Breaks During Intense Exercise: Short breaks allow your body to recover and clear out some of the accumulated lactic acid, reducing the burn you feel.
- Proper Hydration: Staying hydrated ensures that your muscles have enough fluid to flush out waste products, including lactic acid, and function efficiently.
- Gradual Warm-Up and Cool-Down: A proper warm-up prepares your muscles for exercise, improving blood flow and oxygen delivery, while a cool-down helps your body return to normal more gradually, reducing lactic acid buildup.
- Pacing Yourself: If you’re new to high-intensity workouts, avoid pushing yourself too hard, too fast. Give your body time to adapt to the demands of anaerobic exercise by gradually increasing the intensity of your workouts.
- Eating a Balanced Diet: Nutritious, carbohydrate-rich foods provide your muscles with the glucose they need during exercise. Consuming complex carbohydrates before a workout helps fuel your muscles and reduce the risk of early fatigue caused by lactic acid buildup.
- Active Recovery: Low-intensity activity, such as walking or cycling, after a hard workout can improve circulation and help your muscles clear out lactic acid faster.
Why We Feel Sore After a Workout: Delayed Onset Muscle Soreness
The burn you feel during a workout is different from the soreness you feel afterward. Lactic acid buildup causes the immediate burning sensation during exercise, but as mentioned earlier, DOMS is what makes your muscles feel sore in the days following a workout.
DOMS is caused by microscopic damage to your muscle fibers, especially when you try new exercises or increase the intensity of your workouts. When your body repairs these muscle fibers, they grow stronger and more resilient, allowing you to handle more challenging workouts in the future.
The Relationship Between Lactic Acid and Endurance: Understanding the Lactate Threshold
The more you train, the better your body becomes at managing lactic acid. Athletes, particularly endurance athletes, develop a higher lactate threshold —the point at which lactic acid begins to accumulate faster than the body can clear it, potentially leading to lactic acid caused symptoms and health risks associated with lactic acidosis due to intense exercise.
- Why It Matters: Raising your lactate threshold means you can exercise at higher intensities for longer periods without experiencing the debilitating effects of lactic acid buildup.
- How to Improve It: Incorporating high-intensity interval training (HIIT) into your routine can help raise your lactate threshold by forcing your body to adapt to higher levels of lactic acid buildup.
Recovery Strategies
Recovering from lactic acid buildup is essential for anyone engaging in intense exercise. Here are some effective strategies to help rid your body of lactic acid and reduce muscle soreness:
- Hydration: Drinking plenty of water helps dilute lactic acid and flush it out of your system. Proper hydration ensures that your muscles receive the oxygen and hydrogen ions they need to function efficiently, lowering lactic acid levels.
- Compression: Using compression garments before or after a workout can help squeeze out metabolic waste and stagnant blood, promoting better circulation and recovery.
- Heat Therapy: Applying heat before exercise can activate your muscles and improve performance, making them more efficient at handling lactic acid.
- Cold Therapy: After a workout, cold therapy can calm your nervous system and increase the flow of oxygen-rich blood, aiding in the removal of lactic acid.
- High-Intensity Interval Training: Incorporating high-intensity interval training (HIIT) into your routine can improve your stamina and reduce lactic acid production over time.
- Consistent Training: Gradually increasing the intensity of your workouts allows your body to adapt, reducing lactic acid buildup and improving overall performance.
How to Push Through the Burn
When you feel the burn, it’s tempting to stop or slow down. However, understanding how lactic acid works can help you push through and build endurance.
- Mind Over Matter: Knowing that the burn is a temporary response can give you the mental toughness to keep going. Your body is capable of adapting to high lactic acid levels, and with consistent training, the burn will become less intense over time.
- Focus on Breathing: Taking deep, controlled breaths helps your body deliver more oxygen to your muscles, reducing the need for anaerobic metabolism and lowering the rate of lactic acid production.
- Proper Recovery: While it’s important to push through the burn during a workout, it’s equally important to allow your muscles time to recover afterward. This includes getting enough rest, stretching, and ensuring proper nutrition.
A Clear Bottom Line
Use the information to make one clear adjustment, then judge the result from repeatable performance rather than novelty.
Use It in Practice
A useful checkpoint: Use a starting workload that can be repeated with consistent technique. The most useful progression is often modest: an extra repetition, a small load increase, or slightly more total work.
