Hi eric,
as hotasfrick mentioned this would be better asked in the male sexual health forum, but I will answer you here anyway. There are some guys who ejaculate when under incredible physical strain. Here's a similar example, I bodybuild and train... One kid that I was training would always ejaculate while lifting weight. It became such a problem he had to begin wearing a condom or the gym or stuffing his underwear with tissue paper. Only when pushing heavy weight would it happen.
It is nothing to be alarmed about. The male's penis always has some ejaculant in it and once under pressure.. (i.E. When contracting from a large stool) semen can come out.
This is usually from a weak pc muscle. (puboccocceygeus muscle) which can become weaker with age.
I hope this helps reduce your concerns.
Be safe,
justin
