The instruction given was "breathe in through your nose, aim at getting the air to the lower part of your lungs; allow the air to go under here [investigator's hand over the subject's epigastric/subcostal region] and breathe out by gently blowing against your loosely closed lips, as if you are blowing a candle flame so that it bends but doesn't blow out.

Breathe in when squeezing the muscle; breathe out on the release.