Sleep is an essential component to maintaining health. In children, sleep is also vital for growth and development. Ongoing sleep deprivation has been linked to an increased risk for some chronic health problems. In addition, sleep deprivation has been shown to correlate with both increased susceptibility to illness and slower recovery times from illness.[48] In one study, people with chronic insufficient sleep, set as six hours of sleep a night or less, were found to be four times more likely to catch a cold compared to those who reported sleeping for seven hours or more a night.[49] Due to the role of sleep in regulating metabolism, insufficient sleep may also play a role in weight gain or, conversely, in impeding weight loss.[50] Additionally, in 2007, the International Agency for Research on Cancer, which is the cancer research agency for the World Health Organization, declared that "shiftwork that involves circadian disruption is probably carcinogenic to humans," speaking to the dangers of long-term nighttime work due to its intrusion on sleep.[51] In 2015, the National Sleep Foundation released updated recommendations for sleep duration requirements based on age and concluded that "Individuals who habitually sleep outside the normal range may be exhibiting signs or symptoms of serious health problems or, if done volitionally, may be compromising their health and well-being."[52]
The Bhagavad Gita ('Song of the Lord') is part of the Mahabharata and also contains extensive teachings on Yoga. According to According to Mallinson and Singleton, the Gita "seeks to appropriate yoga from the renunciate milieu in which it originated, teaching that it is compatible with worldly activity carried out according to one's caste and life stage; it is only the fruits of one's actions that are to be renounced."[109] In addition to an entire chapter (ch. 6) dedicated to traditional yoga practice, including meditation,[113] it introduces three prominent types of yoga:[114]

The environment is often cited as an important factor influencing the health status of individuals. This includes characteristics of the natural environment, the built environment and the social environment. Factors such as clean water and air, adequate housing, and safe communities and roads all have been found to contribute to good health, especially to the health of infants and children.[18][29] Some studies have shown that a lack of neighborhood recreational spaces including natural environment leads to lower levels of personal satisfaction and higher levels of obesity, linked to lower overall health and well being.[30] It has been demonstrated that increased time spent in natural environments is associated with improved self-reported health [31], suggesting that the positive health benefits of natural space in urban neighborhoods should be taken into account in public policy and land use.
Later developments in the various Buddhist traditions led to new innovations in yogic practices. The Theravada school, while remaining relatively conservative, still developed new ideas on meditation and yogic phenomenology in their later works, the most influential of which is the Visuddhimagga. The Indic meditation teachings of Mahayana Buddhism can be seen in influential texts like the Yogācārabhūmi-Śāstra (compiled c. 4th century). Mahayana meditation practices also developed and adopted new yogic methods, such as the use of mantra and dharani, pure land practices which aimed at rebirth in a pure land or buddhafield, and visualization methods. Chinese Buddhism developed its own methods, such as the Chan practice of Koan introspection and Hua Tou. Likewise, Tantric Buddhism (also Mantrayana, Vajrayana) developed and adopted tantric methods, which remain the basis of the Tibetan Buddhist yogic systems, including the Six yogas of Naropa, Kalacakra, Mahamudra and Dzogchen.[251]
^ James Mallinson, "Sāktism and Hathayoga," 6 March 2012. PDF file Archived 16 June 2013 at the Wayback Machine [accessed 10 June 2012] pp. 20–21 "The Buddha himself is said to have tried both pressing his tongue to the back of his mouth, in a manner similar to that of the hathayogic khecarīmudrā, and ukkutikappadhāna, a squatting posture which may be related to hathayogic techniques such as mahāmudrā, mahābandha, mahāvedha, mūlabandha, and vajrāsana in which pressure is put on the perineum with the heel, in order to force upwards the breath or Kundalinī."
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.[107] Onesicritus claims those Indian yogins (Mandanis ) practiced aloofness and "different postures – standing or sitting or lying naked – and motionless".[108]
According to Pāṇini, the term yoga can be derived from either of two roots, yujir yoga (to yoke) or yuj samādhau ("to concentrate").[27] In the context of the Yoga Sutras of Patanjali, the root yuj samādhau (to concentrate) is considered by traditional commentators as the correct etymology.[28] In accordance with Pāṇini, Vyasa who wrote the first commentary on the Yoga Sutras,[29] states that yoga means samādhi (concentration).[30]
Genetics, or inherited traits from parents, also play a role in determining the health status of individuals and populations. This can encompass both the predisposition to certain diseases and health conditions, as well as the habits and behaviors individuals develop through the lifestyle of their families. For example, genetics may play a role in the manner in which people cope with stress, either mental, emotional or physical. For example, obesity is a significant problem in the United States that contributes to bad mental health and causes stress in the lives of great numbers of people.[32] (One difficulty is the issue raised by the debate over the relative strengths of genetics and other factors; interactions between genetics and environment may be of particular importance.)
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.[107] Onesicritus claims those Indian yogins (Mandanis ) practiced aloofness and "different postures – standing or sitting or lying naked – and motionless".[108]
Tantra is a range of esoteric traditions that began to arise in India no later than the 5th century CE.[181][note 17] George Samuel states, "Tantra" is a contested term, but may be considered as a school whose practices appeared in mostly complete form in Buddhist and Hindu texts by about 10th century CE.[183] Tantric yoga developed complex visualizations which included meditation on the body as a microcosm of the cosmos. They included also the use of mantras, pranayama, and the manipulation of the subtle body, including its nadis and cakras. These teachings on cakras and Kundalini would become central to later forms of Indian Yoga.[184]
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.[22]
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