Science of yoga

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oxygen consumption in yogic practice at his Kaivalyadhama Health and Yoga Research Center, Lonavla,[1]
c. 1955

The science of yoga is the scientific basis of modern

physiology, and psychology. Yoga's effects are to some extent shared with other forms of exercise,[O 1] though it differs in the amount of stretching involved, and because of its frequent use of long holds and relaxation, in its ability to reduce stress. Yoga is here treated separately from meditation
, which has effects of its own, though yoga and meditation are combined in some schools of yoga.

Yoga has been studied scientifically since the 19th-century

Kuvalayananda
both set up institutes to study yoga systematically.

Yoga helps to maintain bone strength, joint mobility, and joint stability. It improves posture, muscle strength, coordination, and confidence, in turn reducing the risk of injury and bone fracture. As it is generally slow and conducted with awareness, it may be safer than many other sports; but some postures such as

have been reported as causes of injury.

Yoga is also used directly

as therapy, especially for psychological conditions such as post-traumatic stress disorder, but the evidence for this remains weak. Yoga has sometimes been marketed with pseudoscientific claims for specific benefits, when it may be no better than other forms of exercise in those cases;[O 1]
and some claims for its effects on particular organs, such as that forward bends eject toxins from the liver, are entirely unfounded. Reviewers have noted the need for more high-quality studies of yoga's effects.

History

, and Dr B.I. Atreya

In the 19th century, the Bengali physician N. C. Paul began the study of the physiology of yoga with his 1851 book Treatise on Yoga Philosophy, noting that yoga can raise carbon dioxide levels in the blood (hypercapnia).[2][3][4]

Early in the 20th century, two pioneers of

Haṭha yoga acceptable, seeking scientific evidence for the health benefits of yoga postures (asanas) and yoga breathing (pranayama). In 1918, Yogendra founded The Yoga Institute to carry out research on yoga, hoping that a gloss of science would make yoga more acceptable in the West.[P 1][O 2][5] Yogendra expressed his intentions in books such as his 1928 Yoga Asanas Simplified[6] and his 1931 Yoga Personal Hygiene.[7] In 1924, Kuvalayananda founded the Kaivalyadhama Health and Yoga Research Center, combining asanas with gymnastics, and like Yogendra seeking a scientific and medical basis for yogic practices.[8][9]

In 1937, the

science journalist William Broad notes that this finding contradicted the image of yoga as conferring special powers.[11][10]

In 1970 Christopher Hills, his son John, and Kevin Kingsland organized the 'World Conference on Scientific Yoga' in New Delhi, bringing 50 Western scientists together with 800 of India's leading swamis, yogis and lamas to discuss their research and establish a network for the creation of a World Yoga University.[12]

Scope

Yoga as exercise is defined by Merriam-Webster as "a system of physical postures, breathing techniques, and sometimes meditation derived from [traditional] Yoga but often practiced independently especially in Western cultures to promote physical and emotional well-being".[O 3]

The science journalist

yoga therapist, writes that "scientific principles and evidence have demystified so much of the practice" of yoga;[15] her book on the Science of Yoga is principally about the anatomy of yoga asanas,[16] with a chapter on the relationships of the body's systems (anatomy and physiology) to yoga.[17] Psychiatric researchers such as Michaela Pascoe have addressed the effect of yoga on measures of psychological stress and depression.[P 2][P 3]

Broad notes the "diffuse nature of the existing science"[14] with pieces of the metaphorical jigsaw puzzle of scientific knowledge of what yoga actually achieves held in many laboratories around the world. The picture is, Broad writes, confused by the "predatory behaviour"[18] of commercial ventures intent upon promoting themselves;[18] but is being clarified by the American National Institutes of Health, which began funding scientific research into yoga in 1998, leading to reliable reports of studies of yoga's effects on different conditions.[19]

Physical effects

Skeleton and joints

flexes, extends and rotates the vertebral column, helping to prevent or manage back pain.[P 4]

Yoga helps to keep

awareness in the moment; and it stresses doing no harm (ahimsa).[24] The American National Institutes of Health advise practising with a qualified instructor to reduce the chance of injury.[25]

Muscles

Any asana that is held for a period, like the arm-balancing Astavakrasana, builds muscle strength by isometric exercise.[26]

Yoga involves both isotonic activity, the shortening of muscles under load, and (unlike many forms of exercise) also a substantial amount of isometric activity, holding still under load, as in any asana which is held for a period. Isometric exercise builds muscle strength.[26]

One of the applications of science to yoga is the provision of detailed knowledge of the anatomy of the

skeletomuscular system, as it relates to yoga asanas, for yoga teachers and yoga therapists.[27][28][29]

Breathing

Pranayama, yoga breathing

Breathing and posture affect each other, especially through their effects on the

diaphragm.[30] Breathing also affects the autonomic nervous system; quiet breathing slows the heart and reduces blood pressure. Together, these produce a feeling of calmness and relaxation.[31] One way to do this is used in one form of yoga breathing (pranayama): the exhalation is counted to be twice as long as the inhalation, say inhale to a count of 3 and exhale to a count of 6.[32]

Breathing can equally be used to energise the body. The pranayama method of

abdominal breathing, using the diaphragm to make the abdomen move in and out.[33]

Broad notes the "myth" that yoga, and especially pranayama, increases the supply of

fainting. On the other hand, slow pranayama can raise carbon dioxide levels, and increase the uptake of oxygen by the brain.[34]

Physiological effects

Fitness

Yoga can be

Surya Namaskar (the 12-asana Salute to the Sun sequence) ranged from light to vigorous exercise, depending on how it was performed.[c] The average for a session of yoga practice without Surya Namaskar was light or moderate exercise.[d][P 6][P 7]

Cardiovascular health

A 2012 survey of yoga in Australia notes that there is "good evidence"

cardiovascular health, but that there was "little apparent uptake of yoga to address [existing] cardiovascular conditions and risk factors".[P 8] Yoga was cited by respondents as a cause of these lifestyle changes; the survey notes that the relative importance of the various factors had not been assessed.[P 8]

Stress relief

Supta Baddha Konasana. There is evidence that yoga relieves stress by multiple mechanisms.[P 10]

Yoga sessions often end (and sometimes also begin) with a period of relaxation in corpse pose, Shavasana. The activity levels of all the body's muscles, and the motor neurons (nerve cells) that activate them, is reduced as relaxation is practised, except for the diaphragm which is used in breathing; and the breathing rate reduces also.[35]

Yoga has other measurable effects that may be beneficial; for example, it reduces the level of the stress hormone cortisol.[36]

As therapy

There is strong scientific evidence that yoga is a safe and effective additional therapy for people with low back pain.[P 4] On its own, yoga is about as effective as other active treatments for back pain, and more effective at reducing pain and improving function than non-exercise treatments.[37]

Yoga is useful to some extent for

stress and depression,[P 2][P 3] but despite repeated attempts, little or no evidence for benefit for other specific medical conditions. Much of the research on the therapeutic use of yoga, including for depression, has been in the form of preliminary studies or clinical trials of low methodological quality, suffering from small sample sizes, inadequate control and blinding, lack of randomization, and high risk of bias.[P 11][P 12] For example, study of trauma-sensitive yoga has been hampered by weak methodology.[P 13]

Pseudoscience

The

emotional stress accumulates in the lower back muscles. Novella states that "None of those specific claims is based in reality."[O 1]

Notes

  1. ^ The LiveScience website similarly states "Modern-day science confirms that the practice also has tangible physical benefits to overall health benefits".[O 4]
  2. ^ Measured at 3.3 ± 1.6 METs.[P 6]
  3. ^ Larson-Meyer and Enette found a range of 2.9 (light exercise) to 7.4 (vigorous) METs. Curious about the wide range of METs in Surya Namaskar, repeated the study (Mody) which gave the highest value; using "transition jumps, and full pushups", he obtained "agreement" with 6.4 METs.[P 6]
  4. ^ Asanas performed individually provide on average 2.2 ± 0.7 METs; pranayama types performed individually provide just 1.3 ± 0.3 METs; a combined class provided 2.9 ± 0.8 METs.[P 6]

References

Book

  1. ^ Alter 2004, pp. 81–100.
  2. ^ Broad 2012, pp. 20ff.
  3. ^ Singleton 2010, p. 52.
  4. ^ Paul 1882.
  5. ^ Shearer 2020, p. 251.
  6. ^ Yogendra 1928.
  7. ^ Singleton 2010, pp. 116–117.
  8. ^ Alter 2004, p. 31.
  9. ^ Goldberg 2016, pp. 100–141.
  10. ^ a b Broad 2012, pp. 83–85.
  11. ^ Behanan 2002.
  12. ^ "World Yoga Conference". The Times of India. 30 November 1970.
  13. ^ Broad 2012, p. 54.
  14. ^ a b c Broad 2012, p. 217.
  15. ^ Swanson 2019, pp. 6–7.
  16. ^ Swanson 2019, pp. 42–173.
  17. ^ Swanson 2019, pp. 10–41.
  18. ^ a b Broad 2012, p. 218.
  19. ^ Broad 2012, p. 219.
  20. ^ Swanson 2019, p. 12.
  21. ^ Swanson 2019, p. 118.
  22. ^ Powers 2008, pp. 25, 176.
  23. ^ Swanson 2019, p. 63.
  24. ^ Swanson 2019, p. 202.
  25. ^ "Yoga: What You Need To Know". National Institutes of Health. May 2019.
  26. ^ a b Coulter 2007, Chapter 1. Movement: Isotonic and Isometric Activity.
  27. ^ Kaminoff & Matthews 2012.
  28. ^ Long & Macivor 2009.
  29. ^ Swanson 2019.
  30. ^ Coulter 2007, Chapter 2. Breathing. How Breathing Affects Posture.
  31. ^ Coulter 2007, Chapter 2. Breathing. How Breathing Affects The Autonomic Nervous System.
  32. ^ Coulter 2007, Chapter 2. Breathing. 2:1 Breathing.
  33. ^ Coulter 2007, Chapter 2. Breathing. The Bellows Breath and Kapalabhati.
  34. ^ Broad 2012, pp. 85–89.
  35. ^ Coulter 2007, Chapter 10. Relaxation and Meditation. The Corpse Posture.
  36. ^ Swanson 2019, p. 27.
  37. S2CID 236516996
    .

Scientific papers

Other

  1. ^ a b c d e Novella, Steven (31 July 2013). "Yoga Woo". Science-Based Medicine.
  2. Indian Express
    . Mumbai.
  3. ^ "Yoga". Merriam-Webster. Retrieved 25 April 2019.
  4. ^ Salamon, Maureen (30 May 2013). "The Science of Yoga and Why It Works". LiveScience.
  5. ^ Rankin-Box, Denise (18 June 2015). "The science of yoga — what research reveals". Elsevier.
  6. ^ Brody, Jane E. (21 December 2015). "12 Minutes of Yoga for Bone Health". The New York Times.

Book sources


External links