• Hatha Yoga – probably the main form known in the West.  Sometimes it may seem that it comprises only vigorous bendy asanas.  I've even had people say worriedly to me that they can't possibly do yoga as they are too stiff.  Fortunately I can usually offer an alternative view. 

"In The Yoga Upanishads hatha yoga is described as a means of attaining physical and mental purification and balance.  Although hatha yoga is the most commonly known yoga, there is a great misconception about its meaning. Hatha is generally translated as "force" whereas in the yogic literature the word hatha is a combination of two mantras, ham and tham, which correspond to pingala and ida nadis repectively.  So the term hatha yoga means the yoga through which these two forces are balanced.  Ida nadi is one of the three major pranic (energetic) channels within the body and represents the mental force.  Pingala nadi represents the solar, vital energy which manifests in the physical body.  According to this description, hatha yoga is the yoga of channellling the pranas in the body."

Swami Niranjanananda Saraswati  - from "Yoga Darshan - Vision of the Yoga Upanishads".

"Hatha yoga concerns two important and vital systems in the physical body – the solar and lunar forces.  In tantra and in hatha yoga these are known as ida and pingala, representing the mental force and the pranic force.  In the body these forces interact with one another, respectively controlling, guiding and directing the senses of action and of knowledge (shakti and shiva)”.

Swami Satyananda Saraswati

 In Western physiology could it be that pingala nadi represents the sympathetic (fight or flight) nervous system;  and ida nadi corresponds to the parasympathetic system or relaxation response?  Most busy and/or stressed  people have an excess of adrenaline.  So the yoga through which these two these two forces are balanced does seem very relevant here and an excellent introduction to yoga practices.