Although many consider the primary series to be the easiest series of Ashtanga yoga because it is the one that students learn first, it is said that it is actually the most difficult to perfect. This is because it is in the primary series that the student, their mind and their body get used to the system of Ashtanga yoga, and to the reality of practicing yoga every day. From there, progressing on to the next series is easier, as the body is used to daily ashtanga practice. It is simply a case of integrating new postures into an established system. Many students practice the primary series for years before moving on to the next series, the intermediate series, or nadi shodana.
The sequence itself is a progression of postures which promote both strength and flexibility. It begins with forward bends before moving on to twists, hip openers and backbends. These postures and the vinyasas between them build internal heat. It is said that the practice has significant benefits on a number of levels. Mentally, the primary series builds willpower, focus and mind-body awareness. Physically, it strengthens, improves flexibility and detoxifies the organs. Energetically, the poses clear obstacles to free the flow of energy in the nadis, or energy channels of the body.
The Ashtanga yoga method of practicing the primary series is to memorize the postures, and practice them six days per week, following the rhythm and counting of the yogi's own breath, rather than a teacher. This is said to encourage introspection and focus.