There are some Yoga positions (sorry, forgot the names and I loaned the book they are listed in to my friend) that are not good for you to practice. Um, basically any stretch that is not stretching the muscles is bad. So in other words, trying to stretch out lengthen the tendons or anything else is not going to benefit you at all.
But I guess this doesn't help much without the names of the Yoga positions. If I ever get my book back I'll let you know
IronFist
"If you like metal you're my friend" -- Manowar
"I am the cosmic storms, I am the tiny worms" -- Dimmu Borgir
<BombScare> i beat the internet
<BombScare> the end guy is hard.