How does yoga affect the cardiovascular system? Patients with heart failure in particular experience adverse nervous system changes affecting their heart. Yoga exercise, with its emphasis on breathing and stretching has been theorized to benefit the nervous system, and in turn result in positive autonomic nervous system changes in patients with heart failure.
To test this hypothesis, researchers examined the effects of a 12 week yoga therapy program in patients with heart failure. The outcome measures that they examined were blood pressure, heart rate, heart rate variability, and the rate pressure product (systolic blood pressure times the heart rate).
The study looked at 130 patients with heart failure. The patients were randomly divided into two groups. The first group of 65 patients underwent a 12 week yoga therapy program, in addition to standard medical therapy for their heart failure. The other group of 65 patients received only standard medical therapy and did not participate in the yoga therapy program. There were 21 patients in the yoga group who dropped out of the study, and 17 patients in the control group that dropped out of the study.
The researchers found that compared to the control group, the patients participating in the yoga program experienced a significant decrease in heart rate, blood pressure, and rate pressure product. The yoga group also experienced changes in their heart rate variability measurements suggesting a shift to parasympathetic predominance over sympathetic activity on the heart.
The authors of this research study conclude that their results suggest that a 12 week yoga therapy program has beneficial effects in heart failure patients by improving parasympathetic activity and decreasing sympathetic activity on the heart.
But is this really the case? It could very well be that any activity, not just yoga, would have similar results. After all, the researchers looked at one group that participated in supervised, group yoga program lasting 60 minutes, done three times a week. We really don't know if the benefit came from simply getting out of the house and participating in a group activity three times a week, or if the benefit came from the yoga maneuvers. Could it be that participating in bingo, three times a week for an hour, would be just as beneficial? What about weight lifting three times a week for an hour?
The problem with this study is that it doesn't have a valid control group. A better way to test their hypothesis that yoga therapy is of particular value in heart failure patients would be to design a cross-over study with a more appropriate control group. For example, the study would last 24 weeks. The first 12 weeks, group 1 would do yoga, and group 2 would do a group exercise activity lasting just as long but without yoga. During the second 12 weeks, group 1 would do a group exercise activity without yoga, and group 2 would do yoga. This research strategy would come up with more meaningful results regarding whether or not yoga, as opposed to other exercise programs, is of particular benefit to patients with heart failure.
From this research study we can only conclude that doing yoga is better than doing nothing. But we already knew that, so what's the point?
Reference: J Clin Diagn Res. 2014 Jan;8(1):14-6