Your tank top may look modest when you're standing up, but it becomes X-rated as soon as you bend over to do push-ups. To avoid flashing everyone at the gym, check your top view from a variety of different angles before leaving home. Bend forward, reach and lean sideways and do jumping jacks to assess the bounce factor. Even non-impact activities require support, says Taj Harris, a certified personal trainer and group fitness instructor at Crunch gyms in New York City. "I had a woman in one of my spin classes who was rather busty," she says. "Her sports bra didn't fit, and riding the bike was causing her breasts to spill out all over the place. It was very distracting to everyone in the class—including me!" Cleavage-proof tanks have a higher neckline that stylishly limits indecent exposure. For those who require extra support, Bounce offers an option for DDD athletes.