I had a long conversation about how muscles get bigger with 
In the conversation, I called it a post work out hypertrophy, which is a different thing. Post-workout hypertrophy is when the muscles get bigger because you have been stressing them for days while a pump is what happens when there is increased blood flow to the muscles because toxins have been produced particularly lactic acid.
Long story short muscles get bigger right before your eyes with a pump while hypertrophy happens over time.
It is a worthy thing to want to see your muscles look bigger but if you want to understand what is sustainable and what is transient…then stick around.
What is a muscle pump?
Muscle pump is what the fitness community refers to as transient hypertrophy. But Hypertrophy means the growth of a muscle cell and transient means that it does not last. The physiologic process is all a result of the breakdown of glucose without oxygen. When this takes place the muscles produce different waste products that accumulate in the blood around the muscle cell.
The main waste product that causes all of the change is lactic acid. The lactic acid draws fluid in and around the cell making it to become swollen. The blood vessels around the muscles also get wider and can accumulate more blood being pumped from the heart. The feeling you get when you have a pump is that the muscle is full.
What is Glycolysis?
This is a metabolic pathway that leads to the breakdown of glucose to either produce pyruvate or lactic acid (as is produced during workouts) with the use of adenosine triphosphate. The process requires 10 reactions handled by specific enzymes. The use of glycolysis is to utilize the energy in glucose.
When glucose is broken down without oxygen, the product of the pathway is lactic acid instead of pyruvic acid. It is not a new process because it has been seen in older species of organisms. The pathway is linked with other pathways one of which is the pentose phosphate pathway.
Getting a pump?
The best way to get this pump is to carry weight. Bench presses, push-ups and the like. Professional bodybuilders usually lift weights before they go on stage so that they look bigger. If you want to capitalize on this fitness experts suggest that a high number of repetitions should be done in the least amount of time.
This will set the muscles into an aerobic cycle where oxygen is no longer being utilized and lactic acid is being produced. These are called High-volume resistance.
High-volume resistance training means a lot of reps and a lot of sets, typically with shorter rest periods. You can achieve high-volume training by manipulating a few variables:
Is it a good method of building muscle?
What research shows is that working out for a muscle pump may not be the best idea if you are starting. But for those who have built their body before then pumping may be a good option.
For those who are newer to the bodybuilding process, low-volume training may be the way to go. But most trainers suggest using both to your advantage.
CAUTION: This is one extra reason why you should drink adequate amounts of water when working out because the muscle pump is just metabolites accumulated in the muscle. After the workout, you are going to want to clear off those toxins from the bloodstream and pass them out as urine. Having metabolites accumulate that way can cause harm to the muscles and other organs around the body and can affect the health of the person training this way.
Conclusion
My take is that seeking a muscle pump should not be the long-term goal. Working out because you want to be healthy and you want to be fit are better goal to strive for. These will give you better long-term satisfaction in your workout.
The workout pump is because of the breakdown of glucose and other metabolites in the muscle. It is not because the muscle itself is getting bigger it is just fluid gathering around the muscle.