I used to pump way back before Tom Hubbard’s site came online. Then there was only a few pumps to choose from and hardly any information on the subject.
Pumping to me was more a novelty than anything. It felt good at low pressure but I didn’t know the risks then. I had a standard bulb pump and I’d fill it with warm water for more pressure. I’d sit there for 40 mins at a time with max pressure and put tape on the air release hole so that thing would suction onto me.
I pumped for about a year because I was getting siked up about the size increase after a session. Funny how the fat schlong seemed smaller than normal the next day.
To make a long story short …
My opinion is also the oxygen. When you pump you trap the blood and hold it in for periods of time and new blood doesn’t circulate until you end the session. It’s like a turnicate trapping blood at a high pressure.
Jelqing is a constant flow of new blood and oxygen into the penis and that is what growth is all about.