Pump-ocalypse 30srv"The pump" known to all bodybuilders and almost everyone who has ever had a good workout, it; s the height of your workout. The pump is almost drug like, and is just as addicting. The pump is when your muscles swell up during your workout, which is caused from the excessive amount of blood going into the muscle and filling it up the same way you would fill up a water balloon. Your muscles get a very full, tight feeling and your skin becomes tighter