Classical yoga incorporates epistemology, metaphysics, ethical practices, systematic exercises and self-development techniques for body, mind and spirit. Its epistemology (pramana) and metaphysics is similar to that of the Sāṅkhya school. The metaphysics of Classical Yoga, like Sāṅkhya, is mainly dualistic, positing that there are two distinct realities. These are prakriti (nature), which is the eternal and active unconscious source of the material world and is composed of three gunas, and the puruṣas (persons), the plural consciousnesses which are the intelligent principles of the world, and are multiple, inactive and eternal witnesses. Each person has a individual puruṣa, which is their true self, the witness and the enjoyer, and that which is liberated. This metaphysical system holds that puruṣas undergo cycles of reincarnation through its interaction and identification with prakirti. Liberation, the goal of this system, results from the isolation (kaivalya) of puruṣa from prakirti, and is achieved through a meditation which detaches oneself from the different forms (tattvas) of prakirti. This is done by stilling one's thought waves (citta vritti) and resting in pure awareness of puruṣa.
Organized interventions to improve health based on the principles and procedures developed through the health sciences are provided by practitioners trained in medicine, nursing, nutrition, pharmacy, social work, psychology, occupational therapy, physical therapy and other health care professions. Clinical practitioners focus mainly on the health of individuals, while public health practitioners consider the overall health of communities and populations. Workplace wellness programs are increasingly adopted by companies for their value in improving the health and well-being of their employees, as are school health services in order to improve the health and well-being of children.
Since the late 1970s, the federal Healthy People Initiative has been a visible component of the United States’ approach to improving population health. In each decade, a new version of Healthy People is issued, featuring updated goals and identifying topic areas and quantifiable objectives for health improvement during the succeeding ten years, with assessment at that point of progress or lack thereof. Progress has been limited to many objectives, leading to concerns about the effectiveness of Healthy People in shaping outcomes in the context of a decentralized and uncoordinated US health system. Healthy People 2020 gives more prominence to health promotion and preventive approaches and adds a substantive focus on the importance of addressing social determinants of health. A new expanded digital interface facilitates use and dissemination rather than bulky printed books as produced in the past. The impact of these changes to Healthy People will be determined in the coming years.
Modern yoga 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 Rigveda, however, does not describe yoga, and there is little evidence as to what the practices were. Early references to practices that later became part of yoga, are made in Brihadaranyaka Upanishad, the earliest Hindu Upanishad. For example, the practice of pranayama (consciously regulating breath) is mentioned in hymn 1.5.23 of Brihadaranyaka Upanishad (c. 900 BCE), and the practice of pratyahara (concentrating all of one's senses on self) is mentioned in hymn 8.15 of Chandogya Upanishad (c. 800–700 BCE).[note 8] The Jaiminiya Upanishad Brahmana teaches mantra repetition and control of the breath.