We all know that yoga, including Ashtanga yoga, is good for us. But how good?
As it turns out, not sooo good. Physiologically at least, asana practice provides only “mild to moderate” physiological benefits. What do you think, Ashtangis?
For me, I’d agree. Here are the results from a study I conducted during a recent Mysore-style class:
- My heart rate averaged 104 beats per minute and I was in my heart rate zone for only 14 minutes in a 75 minute practice (through Navasana). I burned 104 calories.
- During my traditional exercise program of 45 minutes cardiovascular training and 15 minutes exercising, my average heart rate is 135 and I burn 300 calories.
Sally E. Blank from Washington State University Spokane conducted a real scientific study (of Iyengar yogis – I know what you’re thinking) recently and categorized yoga as “mild to moderate intensity exercise without evidence of a sustained cardiopulmonary stimulus“.
The study is one of the few I’ve seen that actually quantifies the physiological benefits of any form of yoga, and I think it’s pretty interesting. Some of its findings include:
- In a 90-minute practice, the participants burned 100-200 calories.
- Participants were in a fitness heart range for 11-60 minutes in a 90-minute practice (or 55-85% of maximum heart rate).
- Standing asana, inversions and back bends (pushing up to back bends) resulted in the larger physiological response than seated or supine asana.
- Backbend and Warrior postures resulted in the highest heart rates.
- Alignment affected the participants’ ability to maintain backbend with perfect alignment resulting in holding backbend for 90-120 seconds while malaligned backbenders only held the posture for 60 seconds.
- Poor alignment raised blood pressure in many postures, but especially in backbend.
Some of the conclusions of the study were:
- “The general cardiorespiratory responses to asanas were similar to changes observed in subjects who perform weight lifting circuit exercise.”
- “This volume of exercise meets the current public health recommendations for physical activity that provides substantial benefits for reduced risk of cardiovascular disease and improved cardiovascular fitness for sedentary adults.”
- “Steady state heart rate was not sustained for a minimum of 10 minutes during the yoga practice.”
- “Moderate to strenuous yoga vinyasa and jumpings would be expected to promote cardiovascular endurance if the practice was sufficiently long. To achieve optimal cardiorespiratory benefits, the American College of Sports Medicine recommends that exercise include 20-60 minutes of large muscle rhythmic and dynamic activity with a minimum of 10 minutes of activity per session.”
- “Based on this evidence, yoga asanas can be fully integrated into western approaches to exercise prescription for healthy, rehabilitating, and diseased populations. “
The participants in the study were all women, aged 36-49 with a weekly practice of 4-9 hours per week and had practiced Iyengar for 2-16 years. In the study, the yoginis held poses for up to 5 minutes (with no vinyasa between poses). The yoginis did 24 postures over about 1-1/2 hours and were considered “intermediate” level practitioners.
The study also noted that at least 16.5 million people in the United States practice yoga and 77.1% are women.
Physiological Responses To Iyengar Yoga Performed By Trained Practitioners by Sally E. Blank at Washington State University Spokane was published in the February 2006 issue of the Journal of Exercise Physiology.
Thank you to Kelly McGonigal, a yoga therapist in the San Francisco Bay Area, for her exhaustive list of studies on the benefit of yoga.
And to SeaOfClouds for the heart photos.
And, Ashtangis, don’t forget to get your cardio in!