Hatha yoga is practised all over the world, but it is mostly associated with India because it derived from the practices of the Yogis of the Natha Sampradaya tradition, in particular, the teachings of its founder, Matsyendranath. In history, Hatha yoga has texts associated with it that go back to the eleventh century. However, the modern development of Hatha yoga, one that is especially focussed on physical postures known as asanas, really started to take off in the twentieth century. It has since been popularized around the globe as a form of physical exercise which does not always take into account all of its spiritual aspects. To many people, it is a modern form of the practice and is simply referred to as 'yoga' in its generic sense. The yoga school of Tirumalai Krishnamacharya, an Indian ayurvedic healer and Hatha scholar who taught yoga from the 1920s onwards, is often considered to have been central to the rise of this form of yoga in the West.
Unlike other forms of yoga, Yin yoga is characterised by a particularly slow pace with emphasis placed on holding its various poses, known as asanas, for longer. Some experts in this form of yoga are able to maintain their chosen asana for five minutes or so. The practise gained popularity in the West from the 1970s onward, especially as it was taught in North America by pioneers like Paul Grilley and Sarah Powers to supplement other forms of yoga and exercise. According to another well-known practitioner, Paulie Zink, Yin yoga should include every aspect of the Taoist tradition, encompassing both yin and yang. In the main, it is popular because this form of yoga places limited stress on tendons and ligaments, something that means it is comparatively injury-free.