In his Yoga Sutra, makes reference to the spiritual experience gained through the use of herbs as being one of the five methods of yogic accomplishment (4.1). In the same passage he mentions the concept of elixir, or sacred herbal formulations, used by yogis.
Herbs have long played a vital role in helping to reduce chronic stiffness and improve flexibility. Chronic stiffness can be traced back to an imbalance of any of the three doshas (vata, pitta, and kapha), according to traditional Ayurvedic medicine—yet vata is usually the very first suspect. Vata consists of the elements of air and ether and presents the attributes of coldness, dryness, lightness, and mobility.
Elevated vata increases both coldness and dryness, which inhibits flexibility and explains those sometimes stiff morning practices during the vata season of early autumn. Thus, by Ayurvedic definition, a balanced vata can result in improved flexibility in the skeletal muscles and joints. Certain herbs reduce vata either by warming the muscles and joints or by calming nervous system tissues. This, in effect, reduces tension, smoothes muscle contraction, and allows greater control and range of mobility.