Pump It Up
You're halfway through a vigorous 90-minute vinyasa class. As your breath comes faster, sweat pools on your mat, and your muscles quiver with effort, you can't help wondering: Does this count as "cardio"?
When we talk about cardio, we are talking about aerobic exercise—that is, sustained activity that elevates your heart rate into a range at which you're training your heart. "Cardiovascular fitness," sometimes used interchangeably with "cardiorespiratory fitness," isn't a term you hear thrown around much in yoga class. But maybe it should be. Measured by how efficiently the heart moves blood—and therefore oxygen—to the muscles, cardiovascular fitness is considered one of the surest routes to leading a long, healthy life. The heft of scientific evidence shows that fitter people are less likely to suffer from heart disease, diabetes, obesity, and certain cancers. Studies link cardio workouts with better cognitive function, sharper focus, and possible protection against the short-term memory loss that often comes with aging.
What's more, having a fit heart is a matter of overall vitality—the ability to move through your day with vigor and alertness. It's being able to play dodge ball with the kids, climb the front steps with an armload of groceries, and bust a move at your high school reunion. As a yoga practitioner, you might well wonder whether the practice that leaves you feeling so vital and energized is actually improving your fitness.
Attaining cardiovascular fitness requires balancing three components of exercise: intensity, duration, and frequency. To get an idea of whether your yoga practice qualifies as a cardio workout, ask yourself: How intense is your practice? How long are the periods of intensity? And how frequently do you practice?
The American College of Sports Medicine, the leading organization in the field of sports medicine and exercise science, offers some baseline numbers for what it takes to achieve and maintain cardiovascular fitness in healthy adults. Namely, aim for 65 to 90 percent of your maximum heart rate, stay in that range for at least 20 minutes, and do it three to five days per week. But the latest research suggests that the overall volume of exercise—and the balance of these three components—is more important than hitting a particular threshold of intensity, says Dr. Carol Garber, associate professor of movement sciences at Columbia University and co-author of the American College of Sports Medicine's latest position on the quality and quantity of exercise necessary for fitness. "There's more and more evidence that mixing high and low intensities is beneficial," she explains.
In other words, if you're working at a lower intensity, you can balance that with longer duration and greater frequency. Likewise, if you're working at a higher intensity, you can do it for shorter periods of time, or less frequently, and get benefits.
Your heart rate is your most reliable gauge of how intensely you're working. You can get a rough approximation of your maximum heart rate by subtracting your age from 220. These numbers are not accurate for everyone, but if you're 40, you can estimate that your maximum heart rate is about 180, and the window at which you're improving your fitness is between 117 and 162 beats per minute. Of course, unlike treadmills at the gym, yoga mats don't come with built-in heart rate monitors.
In the Zone
To determine whether your practice is putting you in the range at which you're getting cardiovascular benefit, first consider the style of yoga you practice. If your primary practice is restorative or characterized by long holds, it's likely not elevating your heart rate enough—and keeping it there—to qualify as training your heart. But if you have a vigorous practice characterized by continuous movement, such as Ashtanga, power flow, or some other flowing vinyasa practice, the answer is less clear.
To get cardiac benefit, the American College of Sports Medicine recommends continuous, rhythmic, aerobic activities that use large muscle groups. Plenty of yoga styles fit that description, but there isn't a consensus about their cardiac benefit, even among yoga teachers who teach similar styles. "If you take my yoga class, you don't need additional cardio, because your heart rate will reach a healthy range within the first 30 minutes of the 90-minute class," says Lisa Black, the owner of Shakti Vinyasa Yoga studios in Seattle, Bellevue, and Redmond, Washington.
Others say you should do more. "Yoga isn't enough," says Sage Rountree, a yoga teacher and triathlon coach in Chapel Hill, North Carolina, and the author of The Athlete's Guide to Yoga. "Even a fast-paced vinyasa practice won't challenge the heart in the same way as running, swimming, or even fast walking."
And while research has shown that yoga increases muscle strength and flexibility, which are other key components of overall fitness, few trials have tackled the cardiovascular question head on—or yielded conclusive results.
Our curiosity piqued, we recruited three of the fittest yogis we could find to participate in our own informal test: Chad Herst, Devorah Sacks, and Russell Case. The three are longtime Ashtanga Yoga practitioners in their middle to late 30s, and each practices an average of six days a week for 75 minutes at a time.
We asked Tim Fleming, a trainer at Endurance Performance Training Center in Mill Valley, California, to measure the three practitioners' cardiovascular fitness and to help us determine whether their practices meet the guidelines for achieving and maintaining a healthy level of cardiovascular fitness. Although we knew our results wouldn't constitute a conclusive scientific study, we were curious about what the numbers would show.
We gave Herst, Sacks, and Case heart rate monitors and asked them to wear them as they did their regular practice at home. The devices collected the data from a week's worth of home practice sessions, and we sent it to Fleming to analyze. After running the numbers, Fleming determined that the three yoga practitioners averaged sufficient intensity, duration, and frequency in their practice to achieve cardio benefit. While the heart rates they recorded showed that they averaged 57 percent of their maximum heart rates, Fleming explained that "this is overcome by the long duration and high frequency of each session and the high volume each week overall."
Next, we headed to Mill Valley, where Herst, Sacks, and Case each hopped on a treadmill at Endurance Performance Training Center to measure their aerobic power, or VO2 max. The VO2 max test, which measures the volume (V) of peak oxygen (O2) uptake, is the gold standard for determining cardiorespiratory fitness. The results indicate how efficiently oxygen enters your lungs, moves into your bloodstream, and is used by your muscles. The fitter you become, the more efficiently your body transports and uses oxygen, which ups your overall VO2 max. When the results were in, our three subjects scored in the 70th to 80th percentile, meaning that they easily meet the ACSM's definition of fitness. Though these aren't the numbers you'd expect to see from an elite runner, cyclist, or cross-country skier—sports that recruit large muscle groups for substantial periods of time, thus putting greater stress on the cardiovascular system and resulting in a higher level of fitness—Fleming declared our three subjects' fitness levels to be "well above average" by the ACSM's standards and concluded their practices are sufficient to meet the guidelines for maintaining a healthy heart.
If you frequent a vigorous flow class, you've probably noticed that the practice gets easier the more frequently you do it. The first time you go to a power flow class, your heart rate might inch up to 175 beats per minute, but if you go to that same class three times a week for six months, your heart rate might rise to only 160 beats per minute. That's a good thing. It means that your heart muscle is getting stronger in response to the training you're giving it. "Your heart meets the demand as your muscles develop," says Fleming. "These adaptations mean that the heart doesn't have to work as hard anymore." In a nutshell, that's what being cardiovascularly fit is all about.
So does yoga "count" as cardio? The best answer is: It can. "Yoga not only gets your heart pumping, but it also quiets the mind and body, honing an ability to experience a greater sense of well-being," says Dean Ornish, clinical professor of medicine at the University of California, San Francisco, and the founder and president of the nonprofit Preventive Medicine Research Institute in Sausalito, California. "And if you find an exercise you enjoy, the more you'll do it, and the more fit you'll become."
In short, your intuition is probably right: A regular, vigorous practice is likely contributing to your cardiovascular fitness. "If you get your heart rate up and keep it up, you'll get fit," says Fleming. And you don't have to hit the mat six days a week for more than an hour a day, the way our test subjects do. "If you do a variation of their schedule, you too can get the benefits," he says.
To get a cardiac benefit from your own practice, weave 20 minutes of Sun Salutations or other vigorous, flowing practices into your routine at least three days a week. Remember, the definition of cardio exercise is "continuous and rhythmic"; in order to elevate your heart rate, you need to be moving continuously at a pace that feels somewhere between moderate and hard, but sustainable. If you're not sure when you reach your target window, wearing a simple heart rate monitor while you practice, either at home or in class, can give you a sense of how hard you're working. And if you're not getting a cardio benefit from your yoga practice, consider supplementing it with one of the activities on page 97, which will not only give your heart a workout, but might just breathe new life into your time on the mat.
Just take care that your fitness goals don't overshadow the myriad other benefits offered by all types of yoga. While their Ashtanga practice has made them undeniably fit, Case, Herst, and Sacks say that fitness is not the primary reason they do yoga. "You can't deny the physicality of the practice," says Sacks. "But if fitness is your only motivator, you won't get far."
Getting a Read
Whether you choose a heart rate monitor with bells and whistles or with just the basics, wearing one while you practice (or do other activities) will help you gauge how hard you're working—and whether or not you're getting fit.