An unintentional, inconvenient, and messy impediment

So I have had this problem for some time now and I haven't really done a great amount of investigation because I can't seem to find the answers I am looking for, or answers in general. I'm in my early 20's, a student, maintaining physical health, and eating well. Now I haven't been the greatest athlete out there but ever since I've been able to run a mile without stopping I've gotten stronger and have new physical capabilities.One nagging problem I haven't been able to figure out is how to increase my chin up reps. I can do a good amount (10-20), but I want to be able to do more. But before my arms and reach a point of fatigue I begin getting the feeling down under, that feeling when you are about ejaculate. As soon as that feeling reaches a point I have to stop myself, especially if I'm in a public gym, or in a playground doing pull ups on a jungle gym or tree. I want to get past this somehow so I purchased myself a pull up bar and set it up in my room. In my own personal dojo and sanctuary I go beyond this threshold and sure enough it's pretty much an orgasm, but I keep going another 2-5 reps because I want to fight it off but I'm totally winded after the burst. I drop and the hearts beating like mad and I am trying to catch my breath, and my arms feel like they're completely out. I didn't get the bar so I can do this in the privacy of my room (well in the name of science I suppose) but to increase my reps and get rid of this impediment. I have only told a handful of friends about this and all were either disgusted, laughed questionably, or acted like I never spoke. One friend actually reminded me of a Arnold Schwarzenegger body building clip where he say "when I lift it feels like I'm cumming" or something along those lines. I haven't had a chance to discuss this with the governator, so I turn to you at MedHelp. Why does this happen? Is there some kind of mechanism that triggers sexual reaction due to rigorous exercise...? I was thinking it may be something with the core muscles possibly by some stretch reaction are stimulating my goods to the point of orgasm (I am starting chin ups completely unaroused with my only intention being doing chin ups). I'll keep looking into it, but I got to get back to some homework. Hope to hear back soon. Thanks and Happy New Year  

[margypops]

Ypou may want to post this on the fitness forum for a good answer.