People have been practicing yoga for millennia to improve their strength, serenity and wellness, but its roots in ancient Indian philosophy have kept the exercise discipline firmly within the realm of alternative medicine.
However, a growing body of scientific evidence is building the case that the spiritual balance created by yoga provides proven health benefits.
Research has found that yoga can help people who are dealing with health problems as wide-ranging as back pain, chronic headaches, sleeplessness, obesity, neck aches, upset stomach, anxiety, depression and high blood pressure, said Sat Bir Singh Khalsa, an assistant professor of medicine at Harvard Medical School and an associate neuroscientist in the Division of Sleep Medicine at Brigham and Women's Hospital in Boston.
The health benefits mainly stem from yoga's focus on the connection between mind and body, Khalsa said.
"The best evidence really shows that yoga is good at reducing stress and helping people cope with the stress they have," he said. "It improves management of stress both psychologically and physiologically."
The benefits of yoga
According to the US National Institutes of Health, proper yoga practise combines:
Physical postures that participants flow into and then hold, before proceeding to the next posture.
A focus on breathing techniques that make participants more aware of their bodies.
Deep meditation and relaxation, allowing participants to focus on their spirituality.
All of those elements must be in place for people to get the best results for their health and well-being, said Karen Sherman, an affiliate associate professor of epidemiology with the Center for Health Studies in the School of Public Health at the University of Washington.
Indeed, the elements are interlaced, she said. For example, the physical postures can help people become stronger and more flexible, but a yoga practice focusing solely on postures misses out on the original intent.
"Postures were intended to make the body strong enough to be able to sit for hours in meditation, to support the spiritual aspirations," Sherman said.
What yoga can do for you
Yoga can help people deal with body aches and pains, she said, by making them stronger, showing them how to move in a less-painful way and improving their ability to cope with pain and relax.
The relaxation, meditation and breathing of yoga has been shown to improve a person's sense of well-being and can be a good treatment for anxiety and depression, Khalsa said.
Yoga may also help bolster the immune system by lowering stress. "When you reduce stress, you make the body healthier," he said. "When the body is healthy, it is able to use its own defences better."
Khalsa's research has shown that yoga can be very helpful to people undergoing cancer treatment.
"They are under stress because it is a life-threatening disease and because everything related to cancer is stressful," he said. But relieving that stress through yoga can improve someone's quality of life and help the person deal with the rigours of chemotherapy and radiation therapy.
Yoga helps battle obesity
Yoga's focus on awareness of the body also has been shown to help people battle obesity. Researchers at the Seattle-based Fred Hutchinson Cancer Research Center found that people who practise yoga are better able to manage their body weight and have a lower average body mass index than people who don't practise yoga.
But yoga has not been proven a cure-all. Khalsa said that some health claims made about yoga have not yet been borne out by medical research, particularly claims that yoga can help improve the function of specific organs, such as the pancreas or liver.
"That may be true. We don't know," he said. "That's going to take some research."
People interested in improving their health through yoga need to find an experienced teacher who combines the three main elements of yoga, Sherman and Khalsa said.
"Everyone should get an instructor who is experienced and has the traditional yogic principles," Sherman said. "You should be learning how to tune into your body. Yoga is about moving with awareness. That's a skill many of us have to develop."
Different types of yoga
Many different styles of yoga exist. Those suitable for beginners include kundalini, viniyoga and Iyengar, Sherman and Khalsa said.
Be wary of teachers who focus on postures without also emphasising breathing and meditation, particularly if they press students to take on extreme postures, they said. Yoga can cause injury if people push themselves too hard, and such contortions have little to do with the mind-body link that students of yoga are trying to attain.
For this reason, the experts say, people might do better to start their yoga practise at a traditional yoga studio rather than taking yoga through a gym or health club.
"If practising extreme postures and being able to bend yourself into a pretzel were the signs of a good yogi, then the people at Barnum & Bailey Circus would be the best yogis in the world," Khalsa said.
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