None that I am aware of. I am BF DD and go to the gym twice a week, they are high intensity classes. I went back to the gym when she was 8wks.
I make sure she is fed before I squeeze myself into my sports bra and take it off as soon as I get home.
As clover mentioned...just as long as you keep up your fluids and are eating enough which you should do anyway when excercising then it's fine.
Enjoy, it's such a great release when you are feeling a little blahhhhh