In the Ashtanga method, students do not practice asanas on so-called moon days. There are two principles that underlie the tradition. First, we know that the moon affects ocean tides; and second we know that our bodies are roughly 70% water. Given the effect of the moon on the ocean tides we can expect the moon will affect the tides of our physical bodies.
Matthew Sweeney, a student of Shri K. Pattabhi Jois, explains it this way:
"The days preceding the full moon cause an increase in fluid in the body, an internal tide, and generally an increase in energy. As this tends to cause over stimulation, intense practice is not recommended. The days preceding the new moon (sometimes called the dark moon) cause a decrease in fluids in the body. As a tendency there will be less energy, the joints more dry and so an increased chance of injury."
(Sweeney, Matthew. Astanga Yoga As It Is. The Yoga Temple, 2005 (p. 22)).
Tim Miller, another student of Pattabhi Jois, analogizes the phases of the moon to the breath cycle and says:
"Both the sun and moon exert a gravitational pull on the earth. Their relative positions create different energetic experiences that can be compared to the breath cycle. The full moon energy corresponds to the end of the inhalation when the force of prana is greatest. This is an expansive, upward moving force that makes us feel energetic and emotional, but not well grounded. The Upanishads state that the main prana lives in the head. During the full moon we tend to be more headstrong.
The new moon energy corresponds to the end of the exhalation when the force of apana is greatest. Apana is a contracting, downward moving force that makes us feel calm and grounded, but dense and disinclined towards physical exertion.
Practicing Ashtanga Yoga over time makes us more attuned to natural cycles. Observing moon days is one way to recognize and honor the rhythms of nature so we can live in greater harmony with it. "
(Miller, Tim. Ashtanga Yoga Center. Moon Days page at AshtangaYogaCenter.com)
As you practice and move towards a new moon, think about the waning of the moon, the fluids in your body, and the process of exhaling. Are you feeling less energetic, more dry, more grounded, calm, more prone to injury as the moon wanes to new?
As the moon begins to wax towards full, think about the fluids in your body and the process of inhaling. Do you notice an increase in the fluids in your body, an increase in energy, an increase in your emotions and perhaps a feeling of not being well-grounded?
Although the studio may be closed on the new moon and the full moon, there is still plenty of yoga to be done. The asana practice is just one of the 8 limbs of yoga that we practice. On moon days, consider reading and meditating on the yamas and niyamas. Or take one of the yamas (ahimsa, maybe) and try practicing it in your thoughts, words, and deeds throughout the next moon day. Give it the same degree of attention and dedication your give your asana practice and see what happens in your body, mind, and spirit.