Eight yoga claims, examined.Yoga has been touted as a cure-all, promising a slimmer, leaner body, improved cardiovascular health and a hotter sex life. But are popular claims about yoga's endless benefits stretching the truth?
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In the new book "The Science of Yoga: The Risks and the Rewards," William J. Broad, a senior writer for the New York Times and himself a devoted yoga lover, looked at the available science to help establish precisely what yoga can and can't do. "There's a mystique that rolls out of India and all things Eastern, which can get mixed up and produce a powerful image that can be dangerous to the extent that it can be misleading," Broad explains. "The science can be a wonderful tonic and helps clarify what's real and what isn't, what's good and what's bad."
Broad says the ancient form of exercise can do far more good for you than bad, but it's still important to separate fact from fiction. Here are eight common beliefs about yoga-and the study-backed verdicts on which ones are true and which are false.
1. The claim: Yoga is a good cardiovascular workout.
The science is clear: Even vigorous yoga doesn't appreciably strengthen the heart and lungs. Take a 2005 Texas State University study Broad describes in his book. Researchers monitored 26 women as they took a 30-minute hatha yoga class similar to many health club yoga classes. During sun salutations the women reached nearly 35 percent of their maximum oxygen uptake reserve-the difference between how much oxygen they used at the peak level of exercise and how much they used at rest-but only averaged about 15 percent of maximum reserve overall. To put it in context: That's less than the 45 percent of maximum reserve they achieved while walking briskly on a treadmill and well below the recommended 50 to 85 percent recommended by the American College of Sports Medicine to achieve the benefits of aerobic conditioning.
2. The claim: Yoga boosts metabolism.
Actually, the opposite is true. Yoga decreases metabolism. By a lot. One Indian study reported that regular yoga practice cuts basal metabolic rate-how many calories your body burns without doing anything except its basic duties, such as keeping your heart, liver and kidney functioning-by eight percent in men and a full 18 percent in women. All things being equal, this means devoted yogis must eat fewer calories to avoid gaining weight. However, Broad believes it's misleading to focus on metabolism alone for weight control. "Yoga instills discipline and the relaxing aspect can help break stress eating cycles, so often times it can help you lose weight," he explains. "But it does so despite what it's doing to you metabolically-not because of it."
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3. The claim: Yoga floods your body with oxygen.
Nope-this one doesn't hold up under scrutiny either. According to Broad, relaxed breathing increases the body's level of carbon dioxide as fresh air mixes with stale air in the lungs, resulting in less than 10 percent of oxygen being replenished. Fast breathing when done to the point of hyperventilation robs the brain of oxygen by causing blood vessels leading into the brain to constrict and cutting oxygen levels by as much as half. Symptoms such as dizziness, lightheadedness and headaches can result and in extreme cases, can cause hallucinations and fainting, particularly among inexperienced yoga takers.
4. The claim: Yoga doesn't cause injuries.
The truth is that Downward Dogs and Warrior poses cause more than their fair share of aches and pains. Although the data is sparse, the U.S. Consumer Product Safety Commission recorded more than 7,369 yoga-related injuries treated in doctors' offices, clinics and emergency rooms in 2010. That number probably vastly underestimates the number of aching knees, tender backs and sore hips that result in the pursuit of relaxation and enlightenment. While most yoga injuries aren't usually a big deal, Broad warns about one major exception: "There is a lot of big neck flexing that goes on in yoga and this is associated with strokes," he says. His advice? Avoid moves such as shoulder stands and the Plow which place excessive pressure on the neck, and make sure your instructor is experienced enough to adapt the poses to you rather than force you to fit the poses.
5. The claim: Yoga is good for flexibility and balance.
Absolutely! Broad points out that some of the most obvious benefits of yoga such as improved flexibility and balance have been supported by solid science for decades. What may not be so obvious is why these traits are so important, he notes. Poor balance and flexibility contribute to the risk of falling and fracturing a bone, the leading cause of injury death among seniors according to the Centers of Disease Control and Prevention. Most people don't concern themselves with flexibility and balance when they're young, but both fall under the category of "use it or lose it." Yoga is one of the best methods for perfecting and preserving these skills.
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6. The claim: Yoga improves mood.
Yoga can uplift mood and emotions in a profound way by increasing levels of the brain chemical gamma-aminobutyric acid or GABA for short. Low levels of GABA have been associated with mood disorders such as depression and anxiety. In 2007, an elite team of researchers from Harvard Medical School's Mclean Hospital and Boston University Medical School found that hour-long yoga sessions elevated GABA levels by an impressive 27 percent on average-with one subject enjoying an 80 percent increase in the mood-related brain chemical. Yoga is a promising treatment for depression and anxiety, according to Broad.
7. The claim: Yoga is good for your brain.
When thirties screen siren Greta Garbo declared "I vant to be alone," she may have really been craving some private time for yoga. She, along with many other creative types, understood the power of the practice to sharpen the mind. Emerging evidence indicates that yoga lights up the right hemisphere of the brain-the grey matter most associated with inspired thinking, focus and a host of other cognitive rewards. It also seems to quiet the mind so bold thoughts can burst forth. Studies on the subject tend to be small yet intriguing. For example, researchers at the University of Pennsylvania Medical Center in Philadelphia scanned the brains of four inexperienced yogis who practiced Iyengar yoga for about an hour a day and discovered greater activation in the right side of the brain than the left, especially areas associated with setting and achieving goals.
8. The claim: Yoga improves your sex life.
"Yoga is sexually arousing," says Broad. "People who do yoga know this, but they don't talk about it." Although the science is still a little fuzzy on why yoga might get your juices flowing, there's some evidence that it increases circulation in the pubic area, which houses our sexual equipment and where many of our erogenous hormones are produced. Also, certain poses and breathing techniques also seem to prime the body's most important sensual organ-the brain-to pump out hormones associated with arousal and orgasm.
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