We have all felt it before, that burning sensation in the legs during intense activity. Scientists have recently revealed this burning sensation is NOT due to lactic acid (which I will refer to as lactate), however, lactate is surely in our muscles at this point of fatigue, and it goes on to do some remarkable things.
Lactate enters the brain.
To have energy for physical exercise, our body and brain must break down stored energy. Most often, this is via the process of glycolysis- the breakdown of stored carbohydrates (glycogen). And just like burning gasoline creates waste products, so too does this process. In our bodies, this creates lactic acid (known as lactate), which is released into the blood and can reach the liver, the heart, and also the brain.
Research has shown the brain actually prefers this “waste” product over glucose (carbohydrates).
Scientists have infused lactate into subjects when glucose is present and found the glucose is SPARED. In other words, even when glucose was available for use the brain CHOSE lactate. 
This choice does not simply happen by chance, there is a reason.
Our brain is the biggest energy consumer, and just like the rest of our body, its need for energy increases as exercise intensity increases. Lactate can keep your brain working during prolonged aerobic exercise (like a marathon) when your blood sugar (glycogen) is eventually depleted.
Apart from this, the true reasoning behind why lactate is so strongly preferred by the brain is actually unknown, one of the things that makes this so interesting.
However, incredibly, it appears that many of the health benefits that exercise has on the brain like brain cell growth, repair, and ultimately disease prevention may be a result of lactate in the brain.
Lactate helps new brain cells grow
BDNF is a growth factor in our brain, meaning it leads to growth and differentiation of neurons and new connections between neurons. We want AS MUCH of this stuff as we can get, and lactate signals BDNF. 
L-lactate also acts as a signal molecule in the brain to release the chemical norepinephrine from the locus coeruleus to the forebrain. This area controls the sleep-wakefulness state, vigilance, appetite, respiration, emotions, and other autonomic processes. In other words, lactate could explain many of the benefits we see from exercise such as improved mood, appetite control, more energy, and better focus.
Here is why Cytomax (containing lactate) may be an effective post concussion treatment
Traumatic brain injuries like concussions impair glycolysis (explained above) in the glial cells of our brain (the cells that PROTECT our neurons). Normally, these glial cells convert glucose into lactate and then transfer it to neurons to be used as energy. But after the injury, there is an absence of glucose and as a result also no lactate energy for neurons.
So could the benefit of exercise post concussion be a result of our generating of lactate which is, after injury, in shortage?
An observational study of 3,063 student athletes between the ages of 5 and 18 years old confirmed that activity can improve symptoms after a concussion. Students were told not to return to activity until all concussive symptoms like headaches were gone. However, the ones that ignored this advice had the best recovery. Student athletes that returned to exercising within a week were 50 percent less likely to still have concussive symptoms after a month.
Dr. George Brooks, an expert in physiology and lactate metabolism from UC Berkley, was the one who found that lactate is a faster acting fuel source than glucose. This led him to formulate the popular sports energy supplement Cytomax, which contains lactate (in the form of L-Polylactate).
It improves endurance and performance, and may also help heal the brain after traumatic brain injuries by providing the energy that is lacking. Increasing the supply of L-lactate to your neurons immediately after a trauma will reduce neuronal damage and improve recovery.