What is lactate?
Very little is known about lactate in human metabolism, despite its key role in its regulation. For years lactate was thought to be just a waste product from anaerobic exercise. At one time it was even thought that lactate crystallized after exercise causing muscle soreness (not true).
Studies in lactate date back to the 19th century. Nonetheless, scientists began to understand lactates role in exercise and metabolism only in the late 20th century. Most of the information on lactate has come from studies by Dr. George Brooks from the University of California at Berkeley.
Lactate Now
Lactate can form under aerobic conditions. Its production results from glucose utilization by muscle cells. Thanks to Dr. Brooks’ work, we have learned that lactate is not a waste product. It is the most important gluconeogenic precursor in the body. About 30% of all glucose used during exercise is derived from lactate “recycling” to glucose.
- Lactate and metabolism- key regulator of intermediary metabolism, regulating substrate utilization. Lactate decreases and inhibits the breakdown of fat for energy and regulates the rate of glucose utilization by cells
- Lactate and cognitive role are crucial for the brain. Lactate is the main fuel that neurons use. It is essential for long-term memory.
- Lactate and disease- involved in some chronic metabolic diseases like type-2 diabetes, blood lactate levels are 2-3x higher. Cancer cells change metabolism by using too much glucose aerobically. This process produces large amounts of lactate, which can contribute to tumor growth and progression.
Lactate & endurance performance
Lactate is the byproduct of glucose utilization by muscle cells. The higher the glucose intake into the cell, the higher the lactate production. During high intensity exercise, type 2 fast twitch muscle fibers are fully recruited and put to work. Fast twitch muscle fibers use lots of glucose which results in high amounts of lactate. This is a natural byproduct of glucose utilization by skeletal muscle cells.
A well trained endurance athlete is efficient. They export less lactate to the blood because they can clear it in higher amounts right in the lactate-producing muscle. Lactate is cleared mainly by slow-twitch muscle fibers. This is a complex process and can be difficult to understand at first. Fast twitch fibers have a high content of MCT-4 transporters which takes lactate away from the fibers. Slow-twitch fibers have MCT-1 transporters which takes lactate inside. Once inside the cell, lactate is converted into pyruvate in the mitochondria by the enzyme mitochondrial lactate dehydrogenase (mLDH). Then it is synthesized into energy (ATP). Both fast and slow twitch muscle fibers work together.
Zone 2 training (endurance)
Now that all the wonderful scientific understanding of lactate is out of the way…. How exactly do we improve the lactate clearing capacity? Easy! Endurance training! Have you noticed lots of workouts or runs geared towards Zone 2? Yes, and there is a reason for it.
Zone 2 training aims to improve lactate clearance. It does this by increasing the number of mitochondria to clear lactate in the slow-twitch muscle fibers. It also increases the number of MCT-1 and mLDH. Including high-intensity with endurance training increases the number of MCT-4 to increase lactate transport away from fast-twitch fibers. Zone 2 has shown to be the training zone to elicit the best results to improve lactate clearance capacity.
Training Mistakes
The biggest training mistakes many athletes make is to train in the “lactate threshold” to improve lactate clearance capacity. This will not work since fast twitch fibers are the ones producing the lactate. To improve lactate clearance capacity is to train the slow twitch muscle fibers to stimulate mitochondrial growth and role. Training at the lactate threshold effectively enhances glycolytic fibers. It also increases the number and role of these enzymes. But spending too much time at lactate threshold is very tasking and leads to overtraining.
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