In general, EEGs of beginners, who had completed their Hot yoga 40 poses first SKY course one week prior to the study, showed small pockets of synchrony, but Hot yoga 40 poses little whole-brain synchrony Fehmi & McKnight, 2001. Synchrony involves the degree of similarity in the amplitude, frequency, and phase of wave forms when comparing EEG recordings over one region of the brain with recordings over another region Robbins, 2000.
Coherence analysis of the degree of synchrony is used to assess communication between distant brain regions. During rapid breath cycles, EEG disorganization increased and synchrony decreased. During rests after each set of breath cycles, synchrony increased. In practitioners who had done SKY for at least 18 months, baseline synchrony was higher and less subject to disruption during breath practice.
In the most advanced subjects four years or more, alpha bands remained stable over central and peripheral areas with very high degrees of continuous whole-brain synchrony across all 19 channels during breath practices and rest periods see Figure 3.3.