Staying Healthy: Can Yoga Alone Keep Us Fit?

I took my first yoga class after a running injury left me unable to do much else. Imagine my surprise when what I thought would be an hour of light stretching left me sweaty and sore in muscles I didn’t even know I had. But I was hooked—it didn’t take long for me to fall in love and ditch running altogether. While I still do cardio regularly (it’s impossible to avoid it in a hilly city like San Francisco), I wonder if doing yoga alone is enough to keep me out of the gym. It’s a great method of strength training, since many of the asanas (poses) rely on arm and leg strength. But even though I sometimes sweat and breathe heavily through especially challenging sessions, does yoga actually qualify as cardiovascular exercise, too? Is it enough to keep us aerobically fit?

The Role of Oxygen Intake

Those unfamiliar with yoga might make the same mistake I first did: assuming that it calls for only a few gentle bends. Thanks in part to yoga’s increasing popularity, there are many different kinds. For example, Hatha yoga is slow-paced, calming, and perfect for beginners. Ashtanga involves flows (series of asanas) at a faster pace, elevating heart rate and increasing muscle endurance. Power yoga, a variation of Ashtanga, is equally rigorous but uses different flows. Obviously, Ashtanga and Power probably burn more calories than Hatha, but that doesn’t mean Hatha doesn’t have its own fitness benefits.

A 2005 study funded by the nonprofit American Council on Fitness (ACE) and conducted at the University of Wisconsin, La Crosse, divided thirty-four healthy, but inactive, women into two groups: one did fifty-five-minute Hatha yoga sessions three times a week for two months, and the other did nothing. Researchers tested the overall fitness levels of each woman before and after the two-month period. Those who did Hatha had significantly improved levels of flexibility, endurance, balance, and strength. On average, they could do six more push-ups and fourteen more curl-ups than before—and that was just after two months.

Unfortunately, researchers also found that there were barely any changes in their maximum oxygen intake, a measure of how efficiently oxygen moves through the body and is used by muscles (and one way of testing cardiovascular fitness). However, a study at the University of California, Davis, in 2001 did show that practicing yoga regularly increased maximum oxygen intake. Their results, which were published in the journal Preventative Cardiology, showed that when their ten volunteers—all aged eighteen to twenty-seven, and all yoga novices—attended eighty-five-minute Hatha yoga classes twice a week for two months, their maximum oxygen intake went up by as much as 7 percent, and researchers believed that number would have continued rising if the study had lasted longer.

Age might be a factor in the difference between these two studies’ findings, since the average age in the ACE study was thirty-three, and none of the UC Davis participants was over twenty-seven. Or perhaps it lies in the fitness levels of participants in each study: ACE used sedentary participants, whereas the participants at UC Davis were merely untrained in yoga. Either way, it’s clear that the participants in each study came away from their sessions stronger and healthier. But whether a 7 percent increase is enough to qualify Hatha as cardiovascular exercise is less clear.

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Calculating the Caloric Impact

Researchers from the ACE study would say Hatha’s definitely not enough. “You get changes in strength and muscular endurance, flexibility, balance—all those types of things—but in order to improve aerobic capacity you really have to be working in the aerobic training zone,” says John Pocari, PhD, one of the study’s researchers, in an interview with Ace FitnessMatters.

But what about the more intense types of yoga that go beyond Hatha? Pocari and his colleague actually compared the caloric and aerobic effects of doing Hatha versus Power yoga. They asked fifteen experienced practitioners to perform fifty-minute sessions of each and then compared the results. Doing Hatha burned an average of 144 calories, whereas Power burned 237, about the same amount as any other mild aerobic workout would burn. A 2003 Adelphi University study, published in Medicine & Science in Sports & Exercise, reached a similar conclusion about non-Hatha yoga. Thirteen experienced yoga enthusiasts followed a fifteen-minute video of Vinyasa, a series of movements synchronized with breathing. (You find Vinyasa flow in strenuous yoga disciplines like Ashtanga and Power.) Researchers tested their metabolic rates in the process, and the average number of calories burned was similar to that burned while walking or dancing aerobically.

There’s Power in Every Pose

For optimal physical health, experts recommend getting in at least thirty minutes of moderate aerobic exercise each day. I hoped to achieve this by way of a steady yoga practice, but based on science’s findings, that just isn’t enough to give me the kinds of benefits regular jogging, power walking, spinning, and other, more lively forms of cardio provide. We need to get our hearts pumping and our pores sweating, and while challenging forms of yoga do that sometimes, it seems our bodies still need a little more.

Then again, yoga’s not supposed to be a form of cardio anyway—it’s a way to increase mindfulness and relax. When you compromise that, you miss out on some of yoga’s best qualities. And even if it doesn’t provide you with a heart-pumping workout, all these studies have shown that endurance, muscle strength, flexibility, and balance do improve when you do yoga. So to maintain or achieve overall fitness, yoga should definitely be a part of your routine as one of the many ways in which you stay physically active. Variety is the spice of life, after all, and when it comes to exercise, it’s absolutely necessary for physical (and mental) health.