The vacuum hold primarily works the transversus abdominis -- a group of core muscles in your midsection -- and assists in correcting posture. It's a technique that the bodybuilders of yesteryear used in competitions. And while it's a good diversion while you're sitting at a traffic light, you can perform the vacuum hold virtually anywhere, whether you're waiting in line at the grocery store or sitting at home watching television.
To perform the vacuum hold, simply tighten your abdomen and suck in your midsection. "It doesn't relate to holding your breath; you should be able to hold it in while breathing normally," Peterson says. Start by holding the pose for 15 seconds. Over time, work your way up to a 60-second hold [source: Peterson]. You can also time it with the movements in traffic: Tense your midsection when you hit the brakes and release once you start moving again.