If the bands press against your fistula don't use them. However, if you fistula surgery has healed you can lift weights that don't press against the fistula. People are worried that if you press your fistula closed it will clot off. That has happened to some people.
Go to fistulafirst.org for more (and maybe better) info.
You can see the vein used for upper arm fistulas on the biceps of most body builders. There is a body builder on dialysis. He was in the DaVita or NxStage newsletter a year or two ago. A picture of him, Don Long, is at the NxStage Users Forum website.
http://nxstageusers.com/images/galleryout/images/DonLong.jpg