Science of yoga
The science of yoga is the study of modern yoga as physical exercise and yoga breathing (pranayama) in human sciences such as anatomy, physiology, and psychology. Yoga's effects are to some extent shared with other forms of exercise, 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 physiology experiments of N. C. Paul. The early 20th-century pioneers Yogendra and Kuvalayananda both set up institutes to study yoga systematically.
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; 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.