Most think of Lactate (lactic acid) as what causes pain, reduced performance and muscle fatigue:
“It’s a historic mistake,” Brooks said. “It was thought that lactate is made in muscles when there is not enough oxygen. It has been thought to be a fatigue agent, a metabolic waste product, a metabolic poison. But the classic mistake was to note that when a cell was under stress, there was a lot of lactate, then blame it on lactate. The proper interpretation is that lactate production is a strain response, it’s there to compensate for metabolic stress. It is the way cells push back on deficits in metabolism.”
Lactate has been showed to be a major fuel source in your body, your muscles, heart and brain arguably prefer lactate as their main fuel source. Both Xwerks Ignite and Motion contain lactate in their ingredients.
"When lactate is around, as during intense activity, the muscle mitochondria burn it preferentially, and even shut out glucose and fatty acid fuels. Brooks used tracers to show that both the heart muscle and the brain prefer lactate to glucose as fuel, and run more strongly on lactate."