How Do You Pump Up?Pump is a versatile pre-training formula that can be stacked or taken solo. This stim-free formula comes in clutch for the night owls who enter the iron dungeon late into the day, who must avoid caffeine in order to get a good night's rest. On the other hand, Pump can be stacked with your favorite pre-workout in order to enhance the effects and maximize blood flow to deliver maximum nutrients to working muscle groups.