Yoga came to the attention of an educated Western public in the mid-19th century along with other topics of Indian philosophy. In the context of this budding interest, N. C. Paul published his treatise on Yoga Philosophy in 1851.
The first Hindu teacher to actively advocate and disseminate aspects of yoga to a western audience, Swami Vivekananda, toured Europe and the United States in the 1890s. The reception which Swami Vivekananda received built on the active interest of intellectuals, in particular the New England Transcendentalists, among them Ralph Waldo Emerson (1803–1882), who drew on German Romanticism and the interest of philosophers and scholars like G. W. F. Hegel (1770–1831), the brothers August Wilhelm Schlegel (1767–1845) and Karl Wilhelm Friedrich Schlegel (1772–1829), Max Mueller (1823–1900), Arthur Schopenhauer (1788–1860), and others who had (to varying degrees) interests in things Indian.
Theosophists also had a large influence on the American public's view of yoga. Esoteric views current at the end of the 19th century provided a further basis for the reception of Vedanta and of yoga with its theory and practice of correspondence between the spiritual and the physical. The reception of yoga and of Vedanta thus entwined with each other and with the (mostly Neoplatonism-based) currents of religious and philosophical reform and transformation throughout the 19th and early 20th centuries. M. Eliade, himself rooted in the Romanian currents of these traditions, brought a new element into the reception of yoga with the strong emphasis on Tantric Yoga in his seminal book: Yoga: Immortality and Freedom. With the introduction of the Tantra traditions and philosophy of yoga, the concept of the "transcendent" to be attained by Yogic practice shifted from experiencing the "transcendent" ("Atman-Brahman" in Advaitic theory) in the mind, to the body itself.
The American-born yogi, Pierre Arnold Bernard, after his travels through the lands of Kashmir and Bengal, founded the Tantrik Order of America in 1905, after his travels. His teachings gave many westerners their first glimpse into the practices of yoga and tantra.
The modern scientific study of yoga began with the works of N. C. Paul and Major D. Basu in the late 19th century, and then continued into the 20th century with Sri Yogendra (1897–1989) and Swami Kuvalayananda. From 1928, Western medical researchers came to Swami Kuvalayananda's Kaivalyadhama Health and Yoga Research Center to study yoga as a science.
Outside of Buddhist, Hindu and Jain traditions in Asia, the term "yoga" has usually been synonymous with its asanas (postures) or as a form of exercise. In the first half of the 20th century, this aspect of yoga was adopted as a cultural trend in Europe and North America starting . There were periods of criticism and paranoia against yoga as well. By the 1960s, Western interest in Hindu spirituality reached its peak, giving rise to a great number of Neo-Hindu schools specifically advocated to a Western public. During this period, most of the influential Indian teachers of yoga came from two lineages, those of Sivananda Saraswati (1887–1963) and of Tirumalai Krishnamacharya (1888–1989). Teachers of Hatha Yoga who were active in the west in this period included B.K.S. Iyengar (1918–2014), K. Pattabhi Jois (1915–2009), Swami Vishnu-devananda (1927–1993), and Swami Satchidananda (1914–2002). Yogi Bhajan brought Kundalini Yoga to the United States in 1969. Comprehensive, classical teachings of Ashtanga Yoga, Samkhya, the subtle body theory, Fitness Asanas, and tantric elements were included in the yoga teachers training by Baba Hari Dass (1923–), in the United States and Canada.
A second "yoga boom" followed in the 1980s, as Dean Ornish, a follower of Swami Satchidananda, connected yoga to heart health, legitimizing yoga as a purely physical system of health exercises outside of counter-culture or esotericism circles, and unconnected to any religious denomination. Numerous asanas seemed modern in origin, and strongly overlapped with 19th and early-20th century Western exercise traditions.
Since 2001, the popularity of yoga in the USA has expanded. The number of people who practice some form of yoga grew from 4 million (in 2001) to 20 million (in 2011). It has drawn support from world leaders such as Barack Obama who stated, "Yoga has become a universal language of spiritual exercise in the United States, crossing many lines of religion and cultures.
"Every day, millions of people practice yoga to improve their health and overall well-being. That's why we're encouraging everyone to take part in PALA (Presidential Active Lifestyle Award), so show your support for yoga and answer the challenge".
The American College of Sports Medicine supports the integration of yoga into the exercise regimens of healthy individuals as long as properly-trained professionals deliver instruction. The College cites yoga's promotion of "profound mental, physical and spiritual awareness" and its benefits as a form of stretching, and as an enhancer of breath control and of core strength.
Text courtesy of Wikipaedia: https://en.wikipedia.org/wiki/Yoga