Though the gym instructors insist you breathe from the mouth while doing the practice, actually you should only exhale. This is a fine, but an extremely important difference. Because if you inhale, in the ac-ed environs of the gym, u are likely to draw in stuff u don't want inside. I know so many uber-rich types/upper middle class types who have extreme forms of TB -- the ac duct/the box are said to have the sort of temperature that nurtures certain bacilii like the TB-- so unless u want to be infected remember not to inhale from the mouth -- and don't get bullied by the trainer -- some of them are real bullies!!