There's no doubt that exercising can get things moving, and it's especially bad news if you ate a bean burrito before hitting the gym.
If you're worried about passing gas in front of your trainer, be sure to eat something easily digestible at least an hour, or even two, before working out. If you feel rumbling in your tummy, don't be afraid to excuse yourself for a trip to the ladies' room to relieve yourself. And if an accident happens, say "excuse me," make a little joke if it seems appropriate, and move on. We're all human, and although embarrassing, you're probably not the first person who's tooted in front of them.