Asana is the term used to describe the physical postures of yoga, and is probably what most people think of when they hear the term yoga. In this context one of the most obvious purposes of asana is physical exercise. However, in the classical texts, the purpose of asana extends beyond a form of physical exercise. It appears that the classical texts on Hatha yoga see asana as one of the first steps on the ladder to mastery of the mind and higher states.
Asana is the third limb in the eight-fold path of Raja Yoga as given in Patanjali’s Yogasutras. It lists the eight limbs “yama-niyama-asana-pranayama-pratyahara-dharana-dhyana-samadhayah-astau-angani”. The order of listing of the eight limbs reflects a movement from the external outer world, to the subtle aspects of ourselves and our inner worlds.1,2 For example, internal distractions of the mind can be reduced by practising asana before pranayama and meditation as asana can ease physical discomfort in sitting.3
The hatha yogis used asanas as tools for higher awareness. The Hatha Yoga Pradipika (HYP) is a classical text on Hatha Yoga and refers to asana as one of the preliminary steps leading towards spiritual evolution, and the Raja yoga of the mind.4,5 The Gheranda Samhita, another classical text of Hatha yoga, alludes to how training the body is the first step to training the mind. It names 32 asanas said to “give perfection in this mortal world”.6
In the HYP, the remarkable individual benefits of certain asanas are described. Matsyendrasana “destroys all the terrible disease of the body”, Paschimottanasana “…stimulates the gastric fire, makes the loins lean and removes all the diseases of men”. It holds in particular esteem Siddhasana, and advises that it should always be practised. One who “…continually practises the Siddhasana during twelve years, obtains fulfilment” and “When the Siddhasana is mastered, of what use are the various other Asanas?”.4 Similarly, the Gheranda Samhita and Siva Samhita, another classical text, also maintain that performing asanas will lead to a variety of benefits. For example, the Gheranda Samhita says that performing Siddhasana will lead to emancipation, Padmasana will destroy all diseases, Vajrasana will lead to psychic powers and Mrtasana will “destroy fatigue, and quieten the agitation of the mind.” The Siva Samhita says that practising Siddhasana leads to freedom from sin, Padmasana leads to emancipation, Urgrasana “destroys a multitude of miseries”, and Svastikasana is health-giving.6
Although not as dramatic as those listed in some classical texts, modern science has helped us to investigate the physiological benefits of asana. There are multiple benefits which overlap different systems of the body, and just a few of these are discussed below.
Asana practice can help in the use of the body overall in a more balanced way. One of the most immediately thought of and obvious benefits of asana practice is that it improves flexibility and range of movement in different joints. A lack of flexibility can cause issues in the body, for example, tight hamstrings can cause back-pain. Increasing flexibility can help improve and prevent some of these issues.7 Practising asana can also lead to increased muscle strength and endurance.8 Balance is improved by the practice of asana balances, and improved balance can help prevent falls.
Connective tissue and facsica
Fascia is a type of connective tissue that creates the internal framework of the body by connecting, separating, attaching, stabilising and enclosing the muscles and all organs. Asanas engage and release all angles of the body, inspire movement in different directions, encourage relaxation, and effortless and easy breathing. This movement can combat poor posture and facilitate the adaptive gliding of neighbouring fascial sheaths leading to ease in movement.9
Many asanas involve weight-bearing which strengthens bones and can help prevent diseases such as osteoporosis. For example, Warrior II requires weight-bearing in the legs and Downward Facing Dog places weight on the wrists.7 Asana can facilitate healthy alignment of the skeleton by helping the muscular system come back into balance.
There are two branches of the autonomic nervous system, the sympathetic nervous system and the parasympathetic nervous system. Stress-reduction in terms of the nervous system is usually referring to changing the balance from a hypervigilant state mediated by the sympathetic nervous system, to a state of relaxation mediated by the parasympathetic nervous system.7 Gentle and slow asana practice with emphasis on breathing can help activate the parasympathetic nervous system.
The cardio-respiratory system is concerned with the heart, lungs, and blood vessels. Asana can provide moderate exercise for the heart muscle, particularly when they are continuously linked such as Sun Salutations. This makes some types asana practice aerobically challenging.8 In Savasana complete relaxation is provided. This balance of moderate work and complete rest is ideal for the heart. Some asanas help improve the flexibility of the rib area, shoulders, and back, allowing the lungs to expand more fully.
Many asanas have a direct massaging effect on the abdominal area and thus can help with digestion by moving food and waste products through the bowels. Improving posture may also lessen compression of the large intestine which interferes with the normal movement of the stool, so improving bowel function.7
When practising asana the body learns new ways to move and coordinate different actions simultaneously. Along with other practices in yoga, the variety of asana causes the brain to build new synapses, the connections between neurons. Continuing to learn new things into older age increases neuroplasticity and maintains brain function.7
Overall it can be seen that yoga is a holistic discipline so the mechanisms by which the components work are densely interwoven with others. Asanas are interconnected with other systems, so practising taps into different mechanisms that have additive and multiplicative effects. Iyengar says the real importance of asanas lies in the way they train and discipline the mind.10 This synergy may be the most important way of all that yoga heals.