Holding the high 19s as they are called helps to clear the bustline, waistline and back. It also alleviates coughing. Hold the high 19s if you are a singer or if you need to use your voice.
I wish I would have known about the high 19s when I worked in radio. I would have an early morning shift and my voice would be croaky – had I held my high 19s, my voice would have been smooth as silk! Great for singers.