This article looks past the Primary Series to the second Ashtanga sequence, traditionally called Nadi Shodhana. It describes the structure and strong backbending emphasis of the series, examines the difficult and often ego-laden question of readiness, considers the traditional language of nadi purification with care, and is candid that the series has almost no direct research of its own while placing unusually high physical demands on the practitioner.
The question most practitioners do not need to ask
Many practitioners spend years, and sometimes their entire practice lives, working primarily with the Primary Series. There is no requirement within a meaningful Ashtanga practice to keep advancing through the numbered sequences. The urge to move on to the next series is natural, and often it is exactly the urge worth examining rather than obeying. So while this article describes the Intermediate Series, it spends as much time on the harder question of whether and when to approach it at all.
The Intermediate Series is not a reward for the impatient. It is a demanding practice that asks for a settled foundation, and approached too soon it tends to teach injury rather than depth.
What the Intermediate Series is
The second Ashtanga sequence is known in Sanskrit as Nadi Shodhana, most precisely translated as purification of the nadis, or subtle channels. It is also commonly rendered within Ashtanga as nerve purification, though nadis should not be equated directly with anatomical nerves. The same name is used for a well-known alternate-nostril breathing practice; here it refers to the second posture sequence, not the pranayama technique.
Where the Primary Series gives extensive space to forward folding, the Intermediate Series places a much stronger emphasis on backbending, particularly in its first major section. Around this backbending core sits a long sequence of twists, hip work, arm balances, leg-behind-head postures, and headstand variations, all connected through vinyasa. Some of its shapes are famously demanding, none more so than Kapotasana, a backbend so deep that it can take practitioners years to approach with any ease.
Why backbends, and the language around them
The series gives unusual prominence to backbending, while the tradition associates the sequence as a whole with the purification of the nadis and the deepening of breath, bandha, and attention. They are said to maintain the suppleness of the spine and open the front of the body. Some contemporary teachers describe forward bends as confronting ego and backbends as confronting fear; this is a modern interpretive teaching rather than an established physiological principle, and many practitioners do report that deep backbending stirs something emotional, a vulnerability or agitation that is not purely physical.
That emotional dimension can feel very real to the practitioner and is worth acknowledging as experience. It has not, however, been established as a specific physiological effect of backbending, and the talk of clearing the nadis belongs, as with the purification language of the Primary Series, to the tradition's own framework rather than to measured biology. Held that way, it remains meaningful without being oversold.
Knowing when to move on
This is the heart of the article, and the most useful thing I can offer.
In traditional Mysore-style teaching, the Intermediate Series is ordinarily introduced only after a practitioner has established a stable foundation in the Primary Series. The precise threshold varies between teachers, lineages, bodies, and circumstances; there is no single research-based readiness test. Even then, it is introduced the way everything in Ashtanga is introduced, one posture at a time, added to the end of one's Primary practice by a teacher who can see that the ground is ready. Within this traditional method, a student would not ordinarily take up the complete second series independently; new postures are introduced progressively under a teacher's observation.
The reason for this caution is not gatekeeping. The Intermediate postures place real demands on the spine, hips, shoulders, and neck, and a body that has not developed the strength, mobility, and breath control of a solid Primary practice is far more likely to be hurt than helped by them. The honest signals of readiness are unglamorous: a Primary practice that feels sustainable rather than strained, breath that stays steady through the hardest parts of it, and, ideally, an experienced teacher who knows your practice and thinks you are ready. The signal to be most suspicious of is the one that comes from ego, the wish to be seen doing harder postures, or boredom mistaken for readiness.
If there is a single message here, it is that there is no prize for advancing quickly, and a great deal of quiet benefit in deepening what you already have.
The demands, and the strongest cautions yet
Everything said about the Primary Series applies here with more force. Deep backbends load the lumbar spine and can aggravate the lower back if approached without adequate preparation, strength, and guidance. Kapotasana asks for substantial spinal extension together with shoulder mobility, hip extension, strength, and coordinated breath; for many practitioners it requires a long period of carefully adapted preparation. Inversions and headstand variations load the neck. Leg-behind-head postures make heavy demands on the hips, hamstrings, and sacroiliac joint. The combination of repeated loading, large ranges of motion, deep spinal extension, leg-behind-head positions, and complex inversions leaves less room for poorly managed progression. The difficulty of a posture does not make injury inevitable, but it increases the importance of preparation, load management, recovery, and individual adaptation.
The available injury literature offers context but not a direct measure of risk for the Intermediate Series. One survey of Ashtanga Vinyasa practitioners reported injuries most often around the hamstrings, knees, and lower back, but it did not separate practitioners by series or compare Ashtanga with another activity. Imaging studies and published case reports confirm that yoga-related musculoskeletal injuries can occur, yet these sources cannot establish how common they are or whether a particular Ashtanga series is more dangerous than another. The practical case for caution therefore comes primarily from the mechanical demands of the sequence, supported by general injury evidence rather than direct studies of the Intermediate Series. Learn it only with an experienced teacher, never from video alone, and if you have any history of back, neck, shoulder, hip, or sacroiliac trouble, treat entry into this series as a decision to make with both a teacher and, where relevant, a health professional.
What the research says
Here candour is simple: the Intermediate Series has essentially no research of its own.
I could not identify controlled trials that evaluate the complete Ashtanga Intermediate Series as an intervention. Most research on yoga examines far gentler, shorter, or clinically adapted practices, so its findings cannot simply be transferred to this sequence. The general points from earlier articles still hold, that dynamic yoga can support flexibility and fitness, and that yoga more broadly may help mood, but these come from research on far gentler practices and cannot be stretched to cover a sequence of extreme backbends.
So the only honest position is a humble one. Whatever the Intermediate Series offers, and practitioners who love it describe a great deal, those benefits rest on tradition and personal experience rather than on scientific evidence. Its possible harms are at least visible in broader survey, imaging, and case-report literature, while its series-specific benefits have not been measured directly. This does not prove that the practice is more harmful than beneficial; it means that scientific certainty is presently unavailable on either side. That is not a reason to avoid it, but it is a strong reason to approach it slowly, under guidance, and only when the foundation is truly there.
Closing
The Intermediate Series can become hazardous when ambition outruns preparation, but for a suitably prepared practitioner under careful guidance it may represent a meaningful deepening of the method. If you take one thing from this article, let it be that the question is not how to advance, but whether you need to, and that the answer for many practitioners, much of the time, is to keep deepening the practice they already have. In the next article we turn from the sequences themselves to the way Ashtanga is traditionally practised day to day: the Mysore method and the discipline of a regular, self-led practice.
Before then, ask yourself honestly what draws you toward the next series, and whether that same energy could instead go into the practice already under your feet.
References
Selected sources consulted:
Mikkonen, J., Pedersen, P., & McCarthy, P. W. (2008). A survey of musculoskeletal injury among Ashtanga Vinyasa yoga practitioners. International Journal of Yoga Therapy, 18(1), 59–64. https://doi.org/10.17761/ijyt.18.1.l0748p25k2558v77
Le Corroller, T., Vertinsky, A. T., Hargunani, R., et al. (2012). Musculoskeletal injuries related to yoga: Imaging observations. American Journal of Roentgenology, 199(2), 413–418. https://doi.org/10.2214/AJR.11.7440
Cramer, H., Krucoff, C., & Dobos, G. (2013). Adverse events associated with yoga: A systematic review of published case reports and case series. PLOS ONE, 8(10), e75515. https://doi.org/10.1371/journal.pone.0075515
Ashtanga Yoga: Nadi Shodhana, the Intermediate Series. AshtangaYoga.info. (Traditional structure, posture order, and terminology of the second series.) https://www.ashtangayoga.info/ashtanga-yoga/intermediate-series-nadi-shodhana/
Note: No controlled studies specifically examining the complete Ashtanga Intermediate Series were identified during the preparation of this article. The available injury literature is general rather than series-specific and cannot compare the risk of one Ashtanga series with another. The traditional language of nadi purification belongs to the method's own framework rather than to a measured physiological mechanism. These summaries reflect sources available at the time of writing.