Yoga is thought to reduce stress; however, few studies have quantified plasma levels of stress hormones. Yoga includes physical postures, meditation, and pranayama (controlled breathing) therefore it is difficult to determine which dose and combination of these components is most beneficial. We hypothesized that a single 15 min bout of 6 breaths per minute would be sufficient to cause a reduction in stress hormones. Ten young healthy males (age 18–35, n=10) were instrumented with brachial arterial catheter for blood draws and respiration was monitored continuously using a double pneumobelt. Blood draws were taken after 15 min of supine rest with baseline ventilation and again after 15 min of slow paced breathing. Average baseline supine respiratory rate was 12.1 ± 0.5 breaths/min and during slow breathing it was 5.5 ± 0.4 breaths/min (p<0.05). After 15 min of slow breathing in the supine position there was a significant reduction in arterial norepinephrine (173.9 ± 15.5 vs 135.6 ± 42.9, p=0.002), cortisol (8.2 ± 0.7 vs 7.3 ± 0.59, p=0.002), and adrenocorticotrophic hormone (ACTH, 15.5 ± 2.4 vs 13.4 ± 2.2, p=0.009). As well, there was a trend for reduction in arterial epinephrine (82 ±28.2 vs 42.7 ± 9.7, p=0.15). These changes are consistent with a reduction in sympathetic nerve activity and a blunting of cortisol. In summary, acute yogic breathing significantly reduces stress hormones.
Wehrwein, E. A., Johnson, C. P., Charkoudian, N., Wallin, B. G., & Joyner, M. J. (2012). A single, acute bout of yogic breathing reduces arterial catecholamines and cortisol. The FASEB Journal, 26(1 Supplement), 893-16.