The following article is based on pseudoscience, but I have found sometimes that pseudoscience is more useful to the average trainee than complex sciences. I am starting off this blog with very general terms, that will need to be understood to understand my future posts. Think of it as a glossary of sorts.
The Pump, when used as a term by bodybuilders, refers to that skin-splitting, swollen feeling the muscles get when lifting weights. Everybody who has ever lifted weights heavy enough to make a change in their body, knows what a bicep pump acheived by bicep curls feels like.
“Feeling Flat” is the opposite of the pump, and frequently occurs as a result of dieting. It is when a pump is inacheivable, or the muscle appears smaller and weaker, than it was very recently (maybe a day or a week before). Athletes frequently associate being flat, with losing muscle, but that is not NECESSARILY the case. Being flat, frequently means your muscle is depleted of nutrients, such as glycogen (carbs), amino acids (protein). It is a pre-muscle loss state. Being flat will cause you to lift less weight, or lift the same amount for less reps, even when the person has not YET lost any contractile proteins (actual muscle). Think of it this way: Your muscle lives off the nutrients within itself, before it is actually destroyed and burned for energy (kcal).
The pump, conversely, is a pre-muscle gain state. It is when the muscle is loaded, with blood and nutrients.