The Stimulating Breath (also called the Bellows Breath).
The Stimulating Breath is adapted from a yogic breathing technique. Its aim is to raise vital energy and increase alertness.
Inhale and exhale rapidly through your nose, keeping your mouth closed but relaxed. Your breaths in and out should be equal in duration, but as short as possible. This is a noisy breathing exercise.
Try for three in-and-out breath cycles per second. This produces a quick movement of the diaphragm, suggesting a bellows. Breathe normally after each cycle.
Do not do for more than 15 seconds on your first try. Each time you practice the Stimulating Breath, you can increase your time by five seconds or so, until you reach a full minute.
Source of Image: Irene Muller