We examined changes in brain waves and blood levels of serum cortisol during yoga exercise in 7 yoga instructors and found that alpha waves increased and serum cortisol decreased. These two measures were negatively correlated (r = -.83). Comparison with a control group of nonpractitioners is desirable.
Kamei T, Toriumi Y, Kimura H, Ohno S, Kumano H, Kimura K. Decrease in serum cortisol during yoga exercise is correlated with alpha wave activation. Percept Mot Skills. 2000 Jun;90(3 Pt 1):1027-32. doi: 10.2466/pms.2000.90.3.1027. PMID: 10883793.