—Part 2—

We opened the the first installment by asking,

Does science have anything it can teach yoga?

Does yoga need “validated” by science in order to be embraced by more people in the West? Or is it somehow the opposite?

For the answers, we turned to Dr. Hagins who is leading a study on yoga’s effectiveness in combating hypertension that would include an Ashtanga-based yoga program designed by Eddie Stern. Below is the conclusion of the interview.

Another question that’s been raised by people I’ve talked to is bias—of several varieties. Is Western science or medicine biased against findings that might validate yogic practices? How do you ensure against your own biases creeping in? What about any bias among the participants?

There is more genuine threat of bias in the scientific study of yoga than you might imagine—but it is pro-yoga, not anti-yoga.

The vast majority of people investigating yoga from a scientific perspective are yogis who are also scientists. They love something about yoga and want to show that it works using the scientific lens they believe in and have been trained in. For most of them, the long term goal is encouraging individuals to practice yoga and increasing the number of politicians and policy makers who support yoga in our schools, communities and workplaces.

Few people are driven to study something just in order to prove it is not true. And there are practical realities at work for scientists that promote the pro-yoga bias. For example, you are unlikely to obtain ongoing grant funding by showing in an early trial that yoga doesn’t work. No significant change with yoga? Too bad. Study something else. So yes, there is a bias—but if anything it is pro-yoga.

As for bias, good scientific study design is explicitly about eliminating bias to the degree possible. Minimizing bias is reinforced by the process of getting a study published or getting money for a grant.

The scientist allows his/her work to be judged by other scientists as to the degree of bias in the methods. Less than 10% of National Institute of Health grant proposals get funded. The smartest scientists in the country review these applications eliminating studies that have methods allowing the potential for bias. We tried in our study, described above, to eliminate as much bias as possible.

We explicitly measured and can therefore rule out, or control, bias in many of the variables that may impact on the outcome of interest (in this case blood pressure), like diet and level of physical activity.  But there may be variables that impact on blood pressure that differ across the groups that we don’t know about. That is why subjects are randomized.

Whatever those variables are, they are most likely to be even in both groups with randomization and consequently any effects they exert they exert equally on both groups—so no net effect for or against yoga. There are other variables, as you mention, like expectation of the participants, that might bias the outcomes.  So, you measure that. In our study, after the first yoga and conventional exercise class we give the participants a survey which measures what they feel and believe about the intervention’s ability to help their blood pressure. Additionally, we control for the amount of time each group attends class and receives attention from the teachers. We control for the amount of home exercise practice each group does. We control for the level of energy used (calories burned) within each class. You cannot eliminate bias, but good science is all about minimizing it.

I’m not sure you can do this briefly, but can you also give us a sense of where the science is on yoga’s impact on the human body (bodies is perhaps the better word choice)? Is there a general, growing consensus of the benefits—and have you seen that get stronger and do you expect it to continue?