yes they can, your manual will give you specific instructions. You may want to check for excessive wear first. If the bars have been worn excessive or damaged you may want to replace them.
The bars should be installed in alternating directions when new. Then when worn on one side, turn them all the other way still in an alternating patern.
when you reverse bars, use new bolts, remove belts on cylinder, make sure all crap is off off cylinder, spin cylinder when you are done switching bars, spin cylinder, cylinder if in balance should stop in any spot if in balance, if cylinder rotates to top, you will need to add some weight to that bar, its trial and error