Penile Ballooning, Endorphin and Lasting Longer.

Penile Ballooning, Endorphin and Lasting Longer.
Penile Ballooning is to create the multiple-stage erection. In the 2nd stage erection, the penile tissue releases two groups of  chemical: prostaglandins and endorphin, which generally activates the adult stem cells for regrowth.
The released prostaglandins naturally include prostaglandin E1, E2, E3,......, and even D2.   In conjunction with the excessive dopamine =>  norepinephrine conversion, prostaglandin E2 may go up faster than E1 and E3, before endorphin exerts its biological cooling effect to counteract the prostaglandin E2.
If your penile tissues release sufficient endorphin from epinephrine, or your serotonin and GABA nervous modulation are effectively to block the dopamine =>  norepinephrine conversion, you will be able to knock down the sympathetic nervous fire.  Generally, if you do penile ballooning alone without porn stimulation, your dopamine =>  norepinephrine conversion should be as usual, not excessive. If you practice both penile ballooning and anal breathing QiGong with a lotus posture at the same time, you will never have any sympathetic fires during the penile balooning practice.
The biochemical reaction chain during the stress response reaction is:
dopamine =>  norepinephrine => epinephrine => beta-endorphin
beta-endorphin actually  cools down and counteracts the sympathetic nervous fire, the effects produced by norepinephrine  epinephrine and its induced prostaglandin E-2.
The simply way to create the beta-endorphin cooling effects is to stretch the pelvic flood muscles,  the thigh's adductor muscles, and the gluteus muscles with a slight pain, as a daily Anal Breathing Qigong exercises. The local blood circulation will circulate endorphin into the penis during erection.
During the penile ballooning,  repeat the following procedures to increase the endorphin release in the penile shaft:
periodically compress or squeeze the erecting penile shaft to force the penile flow to expand the glans, followed by pulling down the scrotum several times; then, pitch the foreskin or the skin around the glans neck. You can include "pitching" into "squeezing."
Just before sex, do the "Frog-Squat Push Up" which extensively spreads and widely opens the hands and legs side way, about 45 degrees from the body center line,  like a swimming frog, for 3-5 minutes.