For the volumetric adjustment procedure, the
participants were asked to wear a nose clip and
breathe in and out 7 times through a mouthpiece
attached to an 800-ml plastic bag, filling and
emptying the bag completely with each breath. This
procedure was conducted in the sitting and standing
posture after appropriate pauses, twice for each
posture, and repeated if participants did not adhere
to instructions, until it was successfully performed.