Potential benefits for adults
While much of the medical community regards the results of yoga research as significant, others point to many flaws which undermine results. Much of the research on yoga has taken the form of preliminary studies or clinical trials of low methodological quality, including small sample sizes, inadequate blinding, lack of randomization, and high risk of bias. Long-term yoga users in the United States have reported musculoskeletal and mental health improvements, as well as reduced symptoms of asthma in asthmatics.There is evidence to suggest that regular yoga practice increases brain GABAlevels, and yoga has been shown to improve mood and anxiety more than some other metabolically-matched exercises, such as walking. The three main focuses of Hatha yoga (exercise, breathing, and meditation) make it beneficial to those suffering from heart disease. Overall, studies of the effects of yoga on heart disease suggest that yoga may reduce high blood-pressure, improve symptoms of heart failure, enhance cardiac rehabilitation, and lower cardiovascular risk factors. For chronic low back pain, specialist Yoga for Healthy Lower Backs has been found 30% more beneficial than usual care alone in a UK clinical trial. Other smaller studies support this finding. The Yoga for Healthy Lower Backs programme is the dominant treatment for society (both cheaper and more effective than usual care alone) due to 8.5 fewer days off work each year. A research group from Boston University School of Medicine also tested yoga’s effects on lower-back pain. Over twelve weeks, one group of volunteers practiced yoga while the control group continued with standard treatment for back pain. The reported pain for yoga participants decreased by one third, while the standard treatment group had only a five percent drop. Yoga participants also had a drop of 80% in the use of pain medication.
There has been an emergence of studies investigating yoga as a complementary intervention for cancer patients. Yoga is used for treatment of cancer patients to decrease depression, insomnia, pain, and fatigue and to increase anxiety control. Mindfulness Based Stress Reduction (MBSR) programs include yoga as a mind-body technique to reduce stress. A study found that after seven weeks the group treated with yoga reported significantly less mood disturbance and reduced stress compared to the control group. Another study found that MBSR had showed positive effects on sleep anxiety, quality of life, and spiritual growth in cancer patients.
Yoga has also been studied as a treatment for schizophrenia. Some encouraging, but inconclusive, evidence suggests that yoga as a complementary treatment may help alleviate symptoms of schizophrenia and improve health-related quality of life.
Implementation of the Kundalini Yoga Lifestyle has shown to help substance abuse addicts increase their quality of life according to psychological questionnaires like the Behavior and Symptom Identification Scale and the Quality of Recovery Index.
Yoga has been shown in a study to have some cognitive functioning (executive functioning, including inhibitory control) acute benefit.
A small percentage of yoga practitioners each year suffer physical injuries analogous to sports injuries;therefore, caution and common sense are recommended. Yoga has been criticized for being potentially dangerous and being a cause for a range of serious medical conditions including thoracic outlet syndrome, degenerative arthritis of the cervical spine, spinal stenosis, retinal tears, damage to the common fibular nerve, “Yoga foot drop,” etc. An exposé of these problems by William Broad published in January, 2012 in The New York Times Magazine resulted in controversy within the international yoga community. Broad, a science writer, yoga practitioner, and author of The Science of Yoga: The Risks and the Rewards, had suffered a back injury while performing a yoga posture.Torn muscles, knee injuries, and headaches are common ailments which may result from yoga practice.
An extensive survey of yoga practitioners in Australia showed that about 20% had suffered some physical injury while practicing yoga. In the previous 12 months 4.6% of the respondents had suffered an injury producing prolonged pain or requiring medical treatment. Headstands, shoulder stands, lotus and half lotus (seated cross-legged position), forward bends, backward bends, and handstands produced the greatest number of injuries.
Some yoga practitioners do not recommend certain yoga exercises for women during menstruation, for pregnant women, or for nursing mothers. However, meditation, breathing exercises, and certain postures which are safe and beneficial for women in these categories are encouraged.
Among the main reasons that experts cite for causing negative effects from yoga are beginners’ competitiveness and instructors’ lack of qualification. As the demand for yoga classes grows, many people get certified to become yoga instructors, often with relatively little training. Not every newly certified instructor can evaluate the condition of every new trainee in their class and recommend refraining from doing certain poses or using appropriate props to avoid injuries. In turn, a beginning yoga student can overestimate the abilities of their body and strive to do advanced poses before their body is flexible or strong enough to perform them.
Vertebral artery dissection, a tear in the arteries in the neck which provide blood to the brain can result from rotation of the neck while the neck is extended. This can occur in a variety of contexts, but is an event which could occur in some yoga practices. This is a very serious condition which can result in astroke.
Acetabular labral tears, damage to the structure joining the femur and the hip, have been reported to have resulted from yoga practice.
It is claimed that yoga can be an excellent training for children and adolescents, both as a form of physical exercise and for breathing, focus, mindfulness, and stress relief: Many school districts have considered incorporating yoga into their P.E. programs. The Encinitas, California school district gained a San Diego Superior Court Judge’s approval to use yoga in P.E., holding against the parents who claimed the practice was intrinsically religious and hence should not be part of a state funded program.
Over time, an extended yoga physiology developed, especially within the tantric tradition and hatha yoga. It pictures humans as composed of three bodies orfive sheaths which cover the atman. The three bodies are described within theMandukya Upanishad, which adds a fourth state, turiya, while the five sheaths (pancha-kosas) are described in the Taittiriya Upanishad. They are often integrated:
- Sthula sarira, the Gross body, comprising the Annamaya Kosha
- Suksma sarira, the Subtle body, composed of;
- the Pranamaya Kosha (Vital breath or Energy),
- Manomaya Kosha (Mind)
- the Vijnanamaya Kosha(Intellect)
- Karana sarira, the Causal body, comprising the Anandamaya Kosha(Bliss)
Within the subtle body energy flows through the nadis or channels, and is concentrated within the chakras.
Yoga compared with other systems of meditation
Zen, the name of which derives from the Sanskrit “dhyaana” via the Chinese “ch’an”[note 25] is a form of Mahayana Buddhism. The Mahayana school of Buddhism is noted for its proximity with yoga. In the west, Zen is often set alongside yoga; the two schools of meditation display obvious family resemblances. This phenomenon merits special attention since yogic practices have some of their roots manifested in the Zen Buddhist school.[note 26] Certain essential elements of yoga are important both for Buddhism in general and for Zen in particular.
In the Nyingma tradition, the path of meditation practice is divided into nineyanas, or vehicles, which are said to be increasingly profound. The last six are described as “yoga yanas”: “Kriya yoga“, “Upa yoga,” “Yoga yana,” “Mahā yoga,” “Anu yoga” and the ultimate practice, “Ati yoga.” The Sarmatraditions also include Kriya, Upa (called “Charya”), and Yoga, with the Anuttara yoga class substituting for Mahayoga and Atiyoga.
Other tantra yoga practices include a system of 108 bodily postures practiced with breath and heart rhythm. The Nyingma tradition also practices Yantra yoga (Tib. “Trul khor”), a discipline that includes breath work (or pranayama), meditative contemplation and precise dynamic movements to centre the practitioner. The body postures of Tibetan ancient yogis are depicted on the walls of the Dalai Lama’s summer temple of Lukhang. A semi-popular account of Tibetan yoga by Chang (1993) refers to caṇḍalī (Tib. “tummo”), the generation of heat in one’s own body, as being “the very foundation of the whole of Tibetan yoga.” Chang also claims that Tibetan yoga involves reconciliation of apparent polarities, such as prana and mind, relating this to theoretical implications of tantrism.
Some Christians integrate yoga and other aspects of Eastern spirituality with prayer and meditation. This has been attributed to a desire to experience God in a more complete way. In 2013, Monsignor Raffaello Martinelli, servicing Congregation for the Doctrine of the Faith, having worked for over 23 years with Cardinal Joseph Ratzinger (Pope Benedict XVI), said that for hisMeditation, a Christian can learn from other religious traditions (zen, yoga, controlled respiration, Mantra): “As long as the Catholic Church rejects nothing of what is true and holy in these religions, we should not despise these indications since non-Christian. Instead, we can collect from them what is useful, provided you never lose sight of the Christian conception of prayer, its logic and requirements, since it is within this that all these fragments must be reformulated and assumed…/…”.Previously, the Roman Catholic Church, and some other Christian organizations have expressed concerns and disapproval with respect to some eastern and New Age practices that include yoga and meditation.
In 1989 and 2003, the Vatican issued two documents: Aspects of Christian meditation and “A Christian reflection on the New Age,” that were mostly critical of eastern and New Age practices. The 2003 document was published as a 90-page handbook detailing the Vatican’s position. The Vatican warned that concentration on the physical aspects of meditation “can degenerate into a cult of the body” and that equating bodily states with mysticism “could also lead to psychic disturbance and, at times, to moral deviations.” Such has been compared to the early days of Christianity, when the church opposed the gnostics’ belief that salvation came not through faith but through a mystical inner knowledge. The letter also says, “one can see if and how [prayer] might be enriched by meditation methods developed in other religions and cultures” but maintains the idea that “there must be some fit between the nature of [other approaches to] prayer and Christian beliefs about ultimate reality.” Some fundamentalistChristian organizations consider yoga to be incompatible with their religious background, considering it a part of theNew Age movement inconsistent with Christianity.
Another view holds that Christian meditation can lead to religious pluralism. This is held by an interdenominational association of Christians that practice it. “The ritual simultaneously operates as an anchor that maintains, enhances, and promotes denominational activity and a sail that allows institutional boundaries to be crossed.” 
In early 11th century, the Persian scholarAl Biruni visited India, lived with Hindus for 16 years, and with their help translated several significant Sanskrit works into Arabic and Persian languages. One of these was Patanjali’s Yogasutras. Al Biruni’s translation preserved many of the core themes of Patañjali ‘s Yoga philosophy, but certain sutras and analytical commentaries were restated making it more consistent with Islamic monotheistic theology. Al Biruni’s version of Yoga Sutras reached Persia and Arabian peninsula by about 1050 AD. Later, in the 16th century, the hath yoga text Amritakunda was translated into Arabic and then Persian. Yoga was, however, not accepted by mainstream Sunni and Shia Islam. Minority Islamic sects such as the mystic Sufi movement, particularly in South Asia, adopted Indian yoga practises, including postures and breath control. Muhammad Ghawth, a Shattari Sufi and one of the translators of yoga text in 16th century, drew controversy for his interest in yoga and was persecuted for his Sufi beliefs.
Malaysia’s top Islamic body in 2008 passed a fatwa, prohibiting Muslimsfrom practicing yoga, saying it had elements of Hinduism and that its practice was blasphemy, thereforeharaam. Some Muslims in Malaysia who had been practicing yoga for years, criticized the decision as “insulting.”Sisters in Islam, a women’s rights group in Malaysia, also expressed disappointment and said yoga was just a form of exercise. This fatwa is legally enforceable. However, Malaysia’s prime minister clarified that yoga as physical exercise is permissible, but the chanting of religious mantras is prohibited.
In 2009, the Council of Ulemas, an Islamic body in Indonesia, passed a fatwa banning yoga on the grounds that it contains Hindu elements. These fatwas have, in turn, been criticized byDarul Uloom Deoband, a DeobandiIslamic seminary in India. Similar fatwas banning yoga, for its link to Hinduism, were issued by the Grand Mufti Ali Gomaa in Egypt in 2004, and by Islamic clerics in Singapore earlier.
In Iran, as of May 2014, according to its Yoga Association, there were approximately 200 yoga centres in the country, a quarter of them in the capitalTehran, where groups can often be seen practising in parks. This has been met by opposition among conservatives.In May 2009, Turkey’s head of theDirectorate of Religious Affairs, Ali Bardakoğlu, discounted personal development techniques such as reiki and yoga as commercial ventures that could lead to extremism. His comments were made in the context of reiki and yoga possibly being a form of proselytization at the expense of Islam.
International Yoga Day
On December 11, 2014, The 193-member U.N. General Assembly approved by consensus, a resolution establishing June 21 as ‘International Day of Yoga‘.