The Pump... It's the sensation that has the dedicated among us coming back to the gym day after day, year after year. But the Pump is much more than a feeling, a fleeting rush... The Pump is essential in our sport, for it signals the start of new muscle growth. With each pump-inducing rep, nutrient-rich blood floods the working muscle cells, engorging them. This process of cell volumization kick starts the anabolic process.