Yoga

Health benefits ascribed to (Yoga) yogasana practice
See also: Yoga (alternative medicine)
Different asanas are recommended by practitioners to cure or prevent problems ranging from constipation to cancer. It is known to reduce stress and other mental worries.

Yoga In the West
Main article: Yoga as exercise
The 2005 "Yoga in America" survey, conducted by Yoga Journal, shows that the number of practitioners in the US increased to 16.5 million with the 18-24 age group, showing a 46% increase in one year.[4

Yoga Pranayama (breathing)
Pranayama
The words prana (life-force) and ayama (to lengthen or regulate) make up pranayama. Pranayama seeks to lengthen, control and regulate the breath. In one variation, the rechak (exhaled air), poorak (inhalation) and kumbhak (retention during normal inhaling and exhaling) are the three parts of the breath that are regulated. Pranayama is practiced to develop mental, physical and spiritual strength. Though the beginner's pranayama is relatively harmless, safely progressing to more advanced practices requires the guidance of a knowledgeable teacher.

Hatha yoga (Sanskrit hayoga, IPA:), also called hatha vidya , is a system of yoga introduced by Yogi Swatmarama, a Hindu sage of 15th century India, and compiler of the Hatha Yoga Pradipika.
The Sanskrit word ha?ha, means "force, violence". ha?hayoga consequently is the term for a forceful, violent style of meditation based on asceticism and self-torture.
Swatmarama introduces his system as preparatory stage of physical purification that the body practices for higher meditation or Yoga. It is based on asanas (postures) and pranayama (breathing techniques, also known as shatkarma). Hatha Yoga became popular in the west beginning in the second half of the 20th century, and is often referred to simply as "Yoga" in the context of health and physical exercise.

Yoga Origins
Siddha Siddhanta Paddhati
The Siddha Siddhanta Paddhati is a very early extant Hatha Yoga Sanskrit text attributed to Gorakshanath by the indigenous tradition which contains much content on the avadhuta, as Feuerstein (1991: p.105) relates:
"One of the earliest hatha yoga scriptures, the Siddha Siddhanta Paddhati, contains many verses that describe the avadhuta. One stanza (VI.20) in particular refers to his chameleon-like capacity to animate any character or role. At times, it is said, he behaves like a worldling or even a king, at other times like an ascetic or naked renunciant."
Detail
The most comprehensive text of hatha yoga is the Hatha Yoga Pradipika by Yogi Swatmarama. This work is nonetheless derived from older Sanskrit texts on yoga besides Yogi Swatmarama's own yogic experiences. It includes information about shatkarma (purification), asana (postures), pranayama (subtle energy control), chakras (centers of energy), kundalini (instinct), bandhas (muscle force), kriyas (techniques; manifestations of kundalini), shakti (sacred force), nadis (channels), and mudras (symbolic gestures) among other topics.
Traditionally, Lord Shiva  is credited with propounding hatha yoga. It is said that on a lonely island, assuming nobody else would hear him, he gave the knowledge of hatha yoga to Goddess Parvati, but a fish heard the entire discourse, remaining still throughout. Lord Shiva took mercy on the fish (Matsya) and made him a siddha, who came to be known as Matsyendranaatha. Matsyendranaatha taught hatha yoga to Chaurangi, a limbless man who was given hands and feet by Matsyendranaatha just by looking at him. Hatha Yoga Pradipika mentions Adi Natha, Matsyendranath, Gorakshanathand many other yogis who became famous hatha yogis.
Many modern schools of hatha yoga derive from the school of Sri Tirumalai Krishnamacharya, who taught from 1924 until his death in 1989. Among his students prominent in popularizing yoga in the West were Sri K. Pattabhi Jois, famous for popularizing the vigorous Ashtanga Vinyasa Yoga style, B.K.S. Iyengar who emphasizes alignment and the use of props, Indra Devi and Krishnamacharya's son T.K.V. Desikachar who developed the Viniyoga style. Desikachar founded the Krishnamacharya Yoga Mandiram in Chennai, with the aim of making available the heritage of yoga as taught by Krishnamacharya.
Another major stream of influence was Swami Sivananda of Rishikesh (1887-1963) and his many disciples including, among others, Swami Vishnu-devananda - founder of International Sivananda Yoga Vedanta Centres; Swami Satyananda - of the Bihar School of Yoga; and Swami Satchidananda - of Integral Yoga.
Concept

Traditional hatha yoga is a holistic yogic path, including disciplines, physical postures (asana), purification procedures (shatkriya), poses (mudra), breathing (pranayama), and meditation. The hatha yoga predominantly practiced in the West consists of mostly asanas understood as physical exercises. It is also recognized as a stress-reducing practice.
Hatha yoga is one of the two branches of yoga that focuses on the physical culture, the other one being raja yoga. Both of these are commonly referred to as sadanga yoga, i.e., yoga of six parts ('sad' meaning six and 'anga' meaning limbs). The six limbs are described below in detail. Svatmarama emphasizes many times in his Hathapradipika text that there is no raja yoga without hatha yoga and no hatha yoga without raja yoga. The main difference is that raja yoga uses asanas mainly to get the body ready for prolonged meditation, and hence focuses more on the meditative asana poses: Lotus Posture (padmasana), Accomplished Posture (siddhasana), Easy Posture (sukhasana) and Pelvic Posture (vajrasana). Hatha yoga utilizes not only meditative postures but also cultural postures. Similarly, raja yoga's use of pranayama is also devoid of extensive locks (bandha).
Hatha represents opposing energies: hot and cold (fire and water, following similar concept as yin-yang), male and female, positive and negative. Hatha yoga attempts to balance mind and body via physical postures or "asanas", purification practices, controlled breathing, and the calming of the mind through relaxation and meditation. Asanas teach poise, balance and strength and are practiced to improve the body's physical health and clear the mind in preparation for meditation. However if an individual has too much phlegm or fat then purification procedures are a necessity before undertaking pranayama.
Ashtanga is the yoga of Patanjali, the compiler of the Yoga Sutras. It is composed of eight limbs: yama and niyama, which are ethical observations; asana; pranayama, which is breath control; pratyahara, which is sense withdrawal; dharana, which is concentration; dhyana, which is meditation; and samadhi, which is a high state of concentration, mastery of the mind. The eight limbs are more precisely viewed as eight levels of progress, each level providing benefits in and of itself and also laying the foundation for the higher levels. Frequently ashtanga yoga of Patanjali is being confused with raja yoga, Patanjali nowhere in his sutras uses the term raja yoga.
Hatha yoga consists of six limbs focused on attaining samadhi. In this scheme, the six limbs of hatha yoga are defined as asana, pranayama, pratyahara, dharana, dhyana and samadhi. The basic text of hatha yoga is Hathapradipika by Swatmarama, a grand disciple of Sahajananda (from the lineage of Sopana, the younger brother of Jnaneshwar Maharaj of Alandi near Pune). An important part of hatha practices is awakening of Kundalini. The signs of success in hatha yoga are slenderness of the body, cheerful face, hearing mystical sound, bright eyes, sense of well-being, control over the bindu, increase in gastric fire and purification of the nadis.