Traditionally both the full and new moon days are observed as rest days in Ashtanga Yoga. When Pattabhi Jois was asked why we should not practice on moon days he was often quoted as saying:
“Two planets [grahas] one place, very dangerous.”
Let me explain this a little more…..
As human beings we are composed of 70% water and are thus influenced by the moon cycle, much like the ebb and flow of the ocean. The phases of the moon are caused by the relative position of the moon to the Sun, both of which exert their gravitational pull upon the Earth. When the moon and the Sun are in opposition, full moons occur. When the moon and the Sun are in conjunction, new moons occur.
Different energetic experiences are thus caused by the relative positions of the Sun and the moon. These energetic experiences can be compared to the breath cycle. Prana is greatest at the end of the inhalation and corresponds to the energy of the full moon. The upward moving expansiveness of Prana heightens our energy and our emotions but as the Upanishads attest, the main prana resides in the head so we tend to be headstrong at this time but ungrounded. This increases our propensity for overexertion and increases the likelihood of injury. Injuries sustain on a moon day are also thought to last longer than those sustained on other days. In contrast, Apana is greatest at the end of the exhalation and corresponds to the energy of the new moon. The downward moving contraction of Apana calms and grounds us but makes us feel dense and less drawn to physical practice.
When we practice Ashtanga over time we learn to recognise, become attuned with and honour the natural rhythms of nature so we can live much more harmoniously with it. When Äsana practice is done six days a week, rest days are essential for rejuvenation, restoration, healing, and growth.