Now here’s another simple pro-tip to work on those abdominal muscles. The ones that are not visible but can give you a flat tummy. In our bodies, transverse abdominals are directly under the rectus abdominals—the six-pack muscle. If you work on this, it will help to flatten your waistline. Use the concept of vacuum to do this i.e. pull your belly button in towards the spine. Hold this movement for about ten seconds and begin breathing normally. Repeat 5 times. In the Indian Yoga system, the Kapaal Bharti also has a similar impact (in addition to other benefits).