Purpose: Inspiratory muscle fatigue is believed to contribute to swimming fatigue (for more on this subject and to view the brief swimming review volume 1 edition 1, see here: http://www.swimmingscience.net/2013/03/brief-swimming-review-volume-1-edition-1.html). Purging allows the athlete to maximally inhale and exhale, training both the inspiratory and expiratory muscles. Directions: A strong exhalation as if you were trying to blow a toy sailboat across a pool, followed by a big but faster inhalation. Make sure you keep the body still, allowing yourself to relax.