Close your eyes. Inhale. Exhale. Ahh. Can you feel your autonomic nervous system modulating itself?

It probably sounds like a weird question. But according to researchers like Harvard Medical School professor Sat Bir S. Khalsa, yoga and meditation practices might actually produce measurable changes in the activity of the autonomic nervous system--the bodily system that regulates, among other things, respiration, pulse rate, and digestion--as well as in brain activity and even gene expression. Researchers like Khalsa believe that these physiological effects, collectively dubbed the "relaxation response," lie at the root of yoga's touted health benefits, and that understanding the relaxation response may prove invaluable in the quest to develop new and improved treatments for sleep disturbances, anxiety disorders, and even some learning difficulties.

A yoga class
A yoga class. Via the Wikimedia Commons, Creative Commons Attribution-ShareAlike 2.0.

Of course, if you're a self-described Type A personality like me, it's easy to view this type of on-demand relaxation as little more than a yogic pipe dream. But curious about how the other half lives, on March 2nd, 2011, I decided to attend a presentation by Khalsa at the Harvard Graduate School of Education entitled Yoga: Practice and Research. I had seen advertisements for the talk plastered around the school, where I am currently studying educational neuroscience, and I was intrigued. Khalsa's evidence-based approach seemed like the perfect way for this high-strung science nerd to enter into the elusive world of yoga and meditation. The promise of attending an actual yoga class following Khalsa's lecture was an added perk. Would I bear witness as my fellow students soared to higher planes of consciousness? Would I finally experience, firsthand, relaxation in its purest form? Only time would tell.

Khalsa began his talk by briefly discussing yoga's history. My fellow attendees and I learned that artifactual evidence suggests that yoga originated in India as many as 5000 years ago. In its traditional form, yoga encompasses rhythmic breathing patterns, physical exercise--including the characteristic, sometimes pretzel-like poses known as "asanas"--and a range of mental activities which, according to Khalsa, lead to a state of "relaxed, focused attention." Although historically yoga has been practiced as a kind of mysticism, with the ultimate goal of reaching a state of "enlightment," in recent years increasing attention has been paid by researchers and the media to yoga's therapeutic potential, both medical and psychological. This positive attention may help to explain yoga's meteoric rise to popularity far beyond the Indian subcontinent. As of 2008, nearly 16 million Americans actively participated in yoga, with a majority of novice practitioners citing wellness or "stress management" as their main motivation for taking up the practice.

As a dyed-in-the-wool data-lover, I found these statistics compelling, but not convincing. Popularity aside, I wondered about the scientific evidence supporting yoga's espoused health benefits. I thus listened with eager ears as Khalsa proceeded to discuss some research findings related to yoga's effects on the body. Surprisingly, I quickly discovered that yoga research is nothing new. A number of landmark studies dating back to the 1930s have looked at the effects of yoga and, relatedly, meditation, on everything from heart rates to brain waves.

While some of these studies yielded conflicting results--it appears that even expert yogis cannot, alas, temporarily stop their own hearts from beating--others provide strong evidence for the existence of the relaxation response. As early as the 1950s, scientists had discovered that yoga and meditation reliably produce a cascade of physiological effects, including decreased oxygen consumption, slowed breathing, increased blood flow to the limbs, and changes in patterns of brain activity associated with attention. Described in a 1971 article as reflecting a "wakeful hypometabolic physiologic state," these effects appear to account for the feelings of subjective calmness and well being reported by yoga and meditation practitioners.

More recently, studies have shown that yoga might actually be as effective as some established forms of psychotherapy for stress-reduction, may have clinical efficacy in the treatment of chronic insomnia and other sleep disorders, may improve some aspects of school performance, and may benefit the treatment of anxiety disorders ranging from performance anxiety in musicians to post-traumatic stress disorder in military veterans. Researchers have also found evidence that yoga and meditation may produce measurable changes in brain regions associated with memory, learning, and mood, and might even lead to changes in the expression of certain genes involved in the body's response to stress.

My confidence in the science behind yoga bolstered, I felt increasingly relaxed (although I can't vouch for my metabolic state) as the lecture ended and Khalsa prepared to lead the group in a short yoga practice. Upon arriving at the talk, I had been immediately struck not only by the number of students who had trekked out on a cold Wednesday night to hear a scientific lecture, but by the number who had arrived dressed in full yoga attire, many carrying their own rolled-up mats. Unlike me, these clearly weren't novices! Slightly intimidated by this amassed expertise, I chose to play the role of reporter and observe the session from the safe confines of a nearby desk. I watched, pen poised, as the lights were dimmed and my peers took their places on the floor.

Lit by the bluish glow of an overhead projector screen, Khalsa began by leading the group in slow chanting, accompanied by a series of "cow" and "cat" poses performed on all fours, backs arched upward. Flipping to the supine position, the group proceeded to raise and lower their legs rapidly, then retract their knees to their chests many times in a row. Khalsa explained that lifting ones legs to different angles is believed by yogis to produce different effects on one's physiological state. Rising from the floor, participants engaged in a set of rapid, frenetic bows, raising their arms in the air and then extending them toward the ground. Afterward, the group again moved to lie on their backs, arms by their sides, in what is known as "corpse pose." Here, Khalsa instructed attendees to focus their attention on different parts of their body, in succession from toes to head. He explained that the goal was to avoid ruminations or intrusive thoughts without "fighting" these thoughts. After several minutes, the group was told to rub their hands and feet briskly, and then hold their knees to their chests and rock rhythmically on their spines. Finally, participants again lay silently in corpse pose for several minutes, then rose to sit cross-legged, hands clasped. The practice ended in traditional fashion, with Khalsa softly calling "namaste" (or "I bow to you") to the group and the group members replying in turn.

Upon returning home and skimming through my notes, I realized that my overall impression of Khalsa's presentation was one of having found both sought-after answers and new questions. The scientific evidence in favor of yoga effectiveness as a relatively low-risk, complementary clinical treatment--or as a means of improving one's overall physical and mental health--appears to be relatively strong. I was also pleasantly surprised to learn that there is a well-understood biological mechanism (the relaxation response) through which these positive effects apparently unfold. However, not having participated in the yoga session myself, I still cannot attest to the practice's touted mellowing side effects. And in the interest of full disclosure, I must report that yoga-by-osmosis did little, if anything, to change my own rumination-prone ways. Nonetheless, attending Khalsa's talk has certainly piqued my curiosity, and I like to think that by the time my next opportunity to try out yoga or meditation rolls around, I will have finally managed to stop worrying and learned to love the "om."

Holly Arthur is a research intern with NOVA. She is currently completing her master's degree in Mind, Brain, and Education at the Harvard Graduate School of Education, where her coursework has focused on the cognitive and affective factors that shape science learning.

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