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Lactic acid, or more accurately lactate, has been blamed for the cause of a burning sensation during intense exercise and the subsequent soreness that accompanies vigorous exertion. It often comes as a surprise to many that it’s responsible for neither of these things. The latest information on lactate has redefined it from a maligned waste product of exercise metabolism to a key adaptation signal and performance enhancer.
Brief review of lactic acid
Lactic acid was first found in dairy milk, hence its association with the word lactation. While the term lactic acid is commonly used, a 2004 study by Roberg et al. published in the American Journal of Physiology: Regulatory, Integrative and Comparative Physiology, showed lactate, not lactic acid, is the actual compound produced in human metabolism.
With intense exercise, aerobic capacity becomes maximized, and hydrogen ions begin to accumulate in muscle cells. These ions cause the pH of the cell to become more acidic and this causes the muscle to burn.
Lactate has the ability to grab these hydrogen ions and actually buffers against the acid pH change. So, while lactate has always been correlated with this muscle burn, it’s now known that it’s not the cause, but instead, a key player in reducing damage.
When lactate is formed it has several fates: It can stay in the cell and be reconverted to energy, it can leave the cell and be used for fuel in other cells, or it can be used to generate glucose for the body in a process called gluconeogenesis. In addition to these effects, lactate can also act on cellular machinery as a cell signaling molecule.
Lactate and energy expenditure
To understand how lactate plays a role in energy metabolism we need to cover a few basics. The ratio of oxygen and carbohydrate used during activity. However, these measurements assume all energy reactions take place in the cellular engines called mitochondria. In fact, some don’t.
To make up for this discrepancy, researchers measured the after-burn of exercise, which is called EPOC (excess post-exercise oxygen consumption). This was done because it was assumed all energy is eventually converted back to aerobic metabolism.
However, this assumption ignored a very important piece of the puzzle. When lactate is formed, heat is released and this heat cannot be captured from gas exchanges.
Anaerobic energy use does not require either oxygen or the mitochondria. When the body switches to anaerobic energy metabolism, a molecule called pyruvate is quickly turned to lactate. This chemical conversion releases heat.
Before lactate can be reconverted to energy, it has to be converted back to pyruvate, which releases more heat. It turns out these conversions and the heat released have important consequences for energy use. It was shown that neglecting lactate in exercise metabolism would underestimate energy production during intense exercise by 40 percent.
Lactate improves metabolic efficiency
Lactate is now suspected to be partly responsible for some of the most beneficial changes produced by exercise. This is believed to come from the potential for lactae to act almost like a hormone.
When exercise intensity rises it’s followed by a large surge in stress hormones. This occurs to supply the body with blood sugar to fuel the intense movement. Intense exercise will quickly max out the aerobic physiology, forcing the body into anaerobic energy production.
When this occurs, pyruvate and hydrogen ions begin to accumulate in the cell. The accumulation of hydrogen ions makes the cell more acidic and causes fatigue and the muscle-burning. This situation causes lactate to be formed.
Lactate then begins to act. It can be made back to glucose (via gluconeogenesis), be converted back to pyruvate and be used as more immediate fuel, and/or stimulate cellular machinery as a signaling molecule.
Lactate’s signal is an “adaptation signal”. It entices the body to begin to set metabolic actions that allow for greater performance. The two chief messages relayed are to increase mitochondrial production and stimulate the release of growth promoting hormones including HGH and testosterone.
These two mechanisms are key for performance enhancement, recovery and body composition changes. The fact that lactate may be a chief promoter of two powerful muscle building and fat burning hormones opens a new world of opportunities for smart training.
Is lactate a hormone?
Many people are confused by this new information, finding it hard to accept lactate has hormone-like action. After all, if it was really acting as a hormone, wouldn’t we have discovered a receptor or something it binds to?
In fact, we have. A lactate receptor called GPR81 was recently isolated in rats, confirming it does indeed act like a hormone. Other studies have shown lactate may not only stimulate growth hormone and testosterone, but may also directly stimulate progesterone as well.
This shows lactate’s key role in helping the body adapt and grow. Testosterone and HGH in particular are key players in human metabolism, increasing lean muscle tissue and decreasing fat mass.
How to use it
Using lactate means embracing the burn. While it’s not the cause of the burn, you will know it’s being produced when a strong burn is elicited. Bodybuilding techniques designed to generate a strong burn are great tools to harness the power of lactate.
These include supersets, compound sets, cheat reps, partial reps, negatives and other well-know techniques. As the world of fitness shifts to a more holistic and fully metabolic approach, the tools of full fatigue workouts utilized by bodybuilders for decades can’t be forgotten. They hold the key to harnessing the power of lactate.