When a male reaches orgasm, and the ejaculate is forced to remain 'inside' or redirected into the bladder, either by clenching or physical manipulation through the taint. This can be physically harmful. First wirteen about approx. 7 years ago in the used to be cool till they sold at and went totally gay Vice Magazine.
I thought maybe if I didn't actually cum I could just go over and over again, so I tried that injaculate thing by pushing hard under my balls when I came. No cum, but it felt fucking weird. Like, taking a piss but with nothing coming out; just isn't right.