According to Crangle, some researchers have favoured a linear theory, which attempts "to interpret the origin and early development of Indian contemplative practices as a sequential growth from an Aryan genesis",[note 4] just like traditional Hinduism regards the Vedas to be the ultimate source of all spiritual knowledge.[note 5] Thomas McEvilley favors a composite model where pre-Aryan yoga prototype existed in the pre-Vedic period and its refinement began in the Vedic period.
Muscle growth is more difficult to achieve in older adults than younger adults because of biological aging, which leads to many metabolic changes detrimental to muscle growth; for instance, by diminishing growth hormone and testosterone levels. Some recent clinical studies have shown that low-dose HGH treatment for adults with HGH deficiency changes the body composition by increasing muscle mass, decreasing fat mass, increasing bone density and muscle strength, improves cardiovascular parameters, and affects the quality of life without significant side effects.[unreliable medical source?]
The number of asanas used in yoga as exercise has increased rapidly from a nominal 84 in 1830, as illustrated in Joga Pradipika, to some 200 in Light on Yoga and over 900 performed by Dharma Mittra by 1984. At the same time, the goals of Haṭha yoga, namely spiritual liberation (moksha) through the raising of kundalini energy, were largely replaced by the goals of fitness and relaxation, while many of Haṭha yoga's components like the shatkarmas (purifications), mudras (seals or gestures including the bandhas, locks to restrain the prana or vital principle), and pranayama were much reduced or removed entirely. The term "hatha yoga" is also in use with a different meaning, a gentle unbranded yoga practice, independent of the major schools, sometimes mainly for women.
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 by Darul Uloom Deoband, a Deobandi Islamic 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.
Yoga as exercise was created in what has been called the Modern Yoga Renaissance by the blending of Western styles of gymnastics with postures from Haṭha yoga in India in the 20th century, pioneered by Shri Yogendra and Swami Kuvalayananda. Before 1900 there were few standing poses in Haṭha yoga. The flowing sequences of salute to the Sun, Surya Namaskar, were pioneered by the Rajah of Aundh, Bhawanrao Shrinivasrao Pant Pratinidhi, in the 1920s. Many standing poses used in gymnastics were incorporated into yoga by Krishnamacharya in Mysore from the 1930s to the 1950s. Several of his students went on to found influential schools of yoga: Pattabhi Jois created Ashtanga Vinyasa Yoga, which in turn led to Power Yoga; B. K. S. Iyengar created Iyengar Yoga, and systematised the canon of asanas in his 1966 book Light on Yoga; Indra Devi taught yoga to many film stars in Hollywood; and Krishnamacharya's son T. K. V. Desikachar founded the Krishnamacharya Yoga Mandalam in Chennai. Other major schools founded in the 20th century include Bikram Choudhury's Bikram Yoga and Swami Sivananda of Rishikesh's Sivananda Vedanta Schools of Yoga. Modern yoga spread across America and Europe, and then the rest of the world.
The earliest references to hatha yoga are in Buddhist works dating from the eighth century. The earliest definition of hatha yoga is found in the 11th century Buddhist text Vimalaprabha, which defines it in relation to the center channel, bindu etc. Hatha yoga synthesizes elements of Patanjali's Yoga Sutras with posture and breathing exercises. It marks the development of asanas (plural) into the full body 'postures' now in popular usage and, along with its many modern variations, is the style that many people associate with the word yoga today.
Alexander the Great reached India in the 4th century BCE. Along with his army, he took Greek academics with him who later wrote memoirs about geography, people and customs they saw. One of Alexander's companion was Onesicritus, quoted in Book 15, Sections 63–65 by Strabo, who describes yogins of India. Onesicritus claims those Indian yogins (Mandanis ) practiced aloofness and "different postures – standing or sitting or lying naked – and motionless".
Health, as defined by the World Health Organization (WHO), is "a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity." This definition has been subject to controversy, as it may have limited value for implementation. Health may be defined as the ability to adapt and manage physical, mental and social challenges throughout life.