An asana is a body posture, originally a sitting pose for meditation, and later in hatha yoga and modern yoga as exercise, adding reclining, standing, inverted, twisting, and balancing poses to the meditation seats. The Yoga Sutras of Patanjali define "asana" as " Patanjali mentions the ability to sit for extended periods as one of the eight limbs of his system.Asanas are also called yoga poses or yoga postures in English.
The 10th or 11th century Goraksha Sataka and the 15th century Hatha Yoga Pradipika identify 84 asanas; the 17th century Hatha Ratnavali provides a different list of 84 asanas, describing some of them. In the 20th century, Indian nationalism favoured physical culture in response to colonialism. In that environment, pioneers such as Yogendra, Kuvalayananda, and Krishnamacharya taught a new system of asanas (incorporating systems of exercise as well as traditional hatha yoga). Among Krishnamacharya's pupils were influential Indian yoga teachers including Pattabhi Jois, founder of Ashtanga vinyasa yoga, and B.K.S. Iyengar, founder of Iyengar yoga. Together they described hundreds more asanas, revived the popularity of yoga, and brought it to the Western world. Many more asanas have been devised since Iyengar's 1966 Light on Yoga which described some 200 asanas. Hundreds more were illustrated by Dharma Mittra.
Asanas were claimed to provide both spiritual and physical benefits in medieval hatha yoga texts. More recently, studies have provided evidence that they improve flexibility, strength, and balance; to reduce stress and conditions related to it; and specifically to alleviate some diseases such as asthma and diabetes.