The moment that Phoebe immersed herself inside the liquid, the liquid began penetrating into her body through the pores that were found on her skin.
When they entered into her body, they managed to enter her bloodstream. Immediately after that, they began activating the cells that were found inside the bloodstream, making them to begin acting faster.
Other than that, the liquid managed to increase the speed at which the blood was moving around the body. And with the increase in the circulation speed of the blood, the metabolic reaction of the body was also increased.
The liquid also began calming the cells that had already been strained by the intense training that Phoebe had been undergoing. The burden that was almost threatening to destroy them was immediately relieved from the cells, and the cells began getting rejuvenated.