Asanas are not immutable. They have evolved throughout history. Up until the 20th century, 84 was accepted as the total number of asanas. Specifically described asanas grew from 8 in Yoga Yajnavalkya to 15 in Hatha Yoga Pradipika to 36 in Gheranda Samhita (see Hatha Yoga Pradipika page). Krishnamacharya approached the 84 figure in the 1930s, describing 70+ asanas in Yoga Makaranda, and in 1941 blew through the magic number with 120+ asanas in Yogasanagulu. By 1966 Iyengar had described and illustrated 200 asanas in Light on Yoga.
Yoga masters of all generations developed their own asanas. Sometimes the asanas were brand new, sometimes they drew from other exercise programs and were adapted to yoga purposes. In my personal practice I use scissors leg lifts as a modification of the standard yoga pose urdhva prasarita padasana. I invented an asana, and if I knew the Sanskrit word for scissors, I could give it an official yoga-sounding name.
Asanas are unique per person: design, selection, sequencing, performing, intensity, duration/repetitions. The asanas to do and ways to do them are unique to each person. Developing an asana practice is as unique as developing a regimen of food and medicines -- it is based on known facts, but selection, dosage, preparation (for taste, nutrition, aesthetics) are unique for an individual.
Body and mind are a vast 3-D network of nodes that makes each of us as a different person. The nodes are bones, muscles, joints, and all organs (including the brain). The nodes are surrounded by tissue and interconnected by communication and logistics systems, including the nervous, respiratory, cardiovascular and lymphatic systems. Data and instructions are transmitted through biochemical and electrical means, including serotonin, endorphins, dopamine, adrenaline, and so forth – basically neurotransmitters, hormones and other key chemicals such as enzymes and minerals. In addition, if you believe in this sort of thing, life energy (qi or prana) flows through channels in the body and is sometimes stored within the body (in chakras, for instance).
Keeping the network functioning effectively is the objective of body and mental health programs, including hatha yoga and countless others. Learn about them, choose one that works for you, and modify it as necessary to satisfy your needs.
