In eight yoga instructors, we examined changes in brain rhythms and natural killer cell activity (NK activity) during yoga exercises. We found that the practice of all three exercises studied resulted in increased alpha activity. There were no apparent changes in NK activity after a series of postural (asana) and meditative (mantra) exercises. During respiratory exercises (pranayama), however, changes in NK activity were observed in the eight subjects, positively correlating to increases in alpha frequencies (r = 0.83, p &lt
0.02). Copyright © 2001 John Wiley &amp
Sons, Ltd.