Its a very demanding job, but a means to earn money still.
There are some tricks like in sports of course, too.
If this is your question better open another thread, which you probably already did.
More interesting here indeed is OP along the lines: Porn is entertainment industry of course. LP films are shot and cut to look good. Where do will still feel its difficult and demanding acts for these girls to perform? Any footage of obvious fear of those big dicks, double penetrations in the same orifice, piss and other things thrown at them on set? Please post scenes!