Increasing Plasma Adrenaline Levels Through Breathing Techniques - an Explorative Study

"Subjects are asked to hyperventilate for an average of 30 breaths. Subsequently, the subjects exhaled and hold their breath for approximately 2 minutes (retention phase). The duration of breath retention will be entirely at the discretion of the subject himself. Breath retention is followed by a deep inhalation breath, that will be held for 10 s. Subsequently a new cycle of hyper/hypoventilation begins."

This exercise consists of deep inhalations and exhalations in which every inhalation and exhalation is followed by breath holding for 10 s, during which the subject tightens all his body muscles.