I'm pretty sure you're talking about the
muscle behind the testicles... Or well,
actually it's not even behind the
testicles. This is called your
pubococcygeus muscle. (or pc muscle for
short).
If it is out of shape then by all means it
will get fatigued just like any other
muscle in your body, and it will ache for
up to 48 hours afterwards---like any other
muscle in your body.
If this is bothersome for you, then you
will have to begin doing pc exercises.
These exercises will also help you control
your ejaculations.
For more details, I googled this article
for you:
http://w
ww.Askmen.Com/love/love_tip_60/67_love_tip
.Html
if you have any questions, feel free to
ask.
Justin