Peak experiences sometimes referred to as flow (e.g., Mihaly Csikszentmihalyi) or by others as being in the zone, have been associated with physiological changes in the body. These may include the release of adrenalin and endorphins, changes in metabolic rates, alteration in patterns of breathing and heart rate, an increase in alpha wave activity, increased energy, and so on. It comes about through a sense of doing something that feels perfectly natural. Aviator Wilbur Wright described it as a sensation of perfect peace mingled with an excitement that strains every nerve to the utmost. (Robinson, Ken, PhD. The Element. p 90-96. NY: Penguin Books, 2009.)