No not really. I wouldn't recommend it.
When your computer degrags, it moves everything on your hard drive to the right place and such.. then if you run anything else.. that program is attempting to read information that is going to or is currently being read/moved by Defrag and thus, slowing both the programs down.
It will just take a longer time and after that, you can possibly still have fragmented files or it'll interrupt and you might have to restart a defrag all over again.