According to Pāṇini, the term yoga can be derived from either of two roots, yujir yoga (to yoke) or yuj samādhau ("to concentrate"). In the context of the Yoga Sutras of Patanjali, the root yuj samādhau (to concentrate) is considered by traditional commentators as the correct etymology. In accordance with Pāṇini, Vyasa who wrote the first commentary on the Yoga Sutras, states that yoga means samādhi (concentration).
Intensive weight training causes micro-tears to the muscles being trained; this is generally known as microtrauma. These micro-tears in the muscle contribute to the soreness felt after exercise, called delayed onset muscle soreness (DOMS). It is the repair of these micro-traumas that results in muscle growth. Normally, this soreness becomes most apparent a day or two after a workout. However, as muscles become adapted to the exercises, soreness tends to decrease.
Ascetic practices, concentration and bodily postures described in the Vedas may have been precursors to yoga. According to Geoffrey Samuel, "Our best evidence to date suggests that [yogic] practices developed in the same ascetic circles as the early sramana movements (Buddhists, Jainas and Ajivikas), probably in around the sixth and fifth centuries BCE."
Yoga gurus from India later introduced yoga to the West, following the success of Swami Vivekananda in the late 19th and early 20th century with his adaptation of yoga tradition, excluding asanas. Outside India, it has developed into a posture-based physical fitness, stress-relief and relaxation technique. Yoga in Indian traditions, however, is more than physical exercise; it has a meditative and spiritual core. One of the six major orthodox schools of Hinduism is also called Yoga, which has its own epistemology and metaphysics, and is closely related to Hindu Samkhya philosophy.
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.
Some Bodybuilders often split their food intake into 5 to 7 meals of equal nutritional content and eat at regular intervals (e.g. every 2 to 3 hours). This approach serves two purposes: to limit overindulging in the cutting phase, and to allow for the consumption of large volumes of food during the bulking phase. Eating more frequently does not increase basal metabolic rate when compared to 3 meals a day. While food does have a metabolic cost to digest, absorb, and store, called the thermic effect of food, it depends on the quantity and type of food, not how the food is spread across the meals of the day. Well-controlled studies using whole-body calorimetry and doubly labeled water have demonstrated that there is no metabolic advantage to eating more frequently.
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.
In Iran, as of May 2014, according to its Yoga Association, there were approximately 200 yoga centres in the country, a quarter of them in the capital Tehran, where groups can often be seen practising in parks. This has been met by opposition among conservatives. In May 2009, Turkey's head of the Directorate of Religious Affairs, Ali Bardakoğlu, discounted personal development techniques such as reiki and yoga as commercial ventures that could lead to extremism. His comments were made in the context of reiki and yoga possibly being a form of proselytization at the expense of Islam.
An increasing number of studies and reports from different organizations and contexts examine the linkages between health and different factors, including lifestyles, environments, health care organization and health policy, one specific health policy brought into many countries in recent years was the introduction of the sugar tax. Beverage taxes came into light with increasing concerns about obesity, particularly among youth. Sugar-sweetened beverages have become a target of anti-obesity initiatives with increasing evidence of their link to obesity.– such as the 1974 Lalonde report from Canada; the Alameda County Study in California; and the series of World Health Reports of the World Health Organization, which focuses on global health issues including access to health care and improving public health outcomes, especially in developing countries.