If you walk through a gym and pay attention on what people are doing you will see some pretty weird stuff. While almost every fitness instructor have his own ideas on what is the best and why it’s not coincidence that they are doing something terribly wrong.
If you do any of these exercises stop immediately, if not, sooner.
IF you want some real exercises for Jiu Jitsu check this link with 21 Strength and Condition exercises for BJJ.
You can also check some bodyweight exercises for BJJ.