The 8 Limbs of Yoga
“Modern yoga” takes place in a class with 10 to 30 others where you will perform a callisthenics and mobility fitness program with a nice nap at the end. I am not saying this is not yoga, it is, but it’s just one part of a much bigger system. What most people call “yoga” is technically just one piece of it: the physical postures, known as asana. Traditionally, yoga was made up of eight parts altogether, not just one.
These eight parts (called the eight “limbs”) were first written down as a complete system in an ancient text called the Yoga Sutras. They build on each other, roughly like this:
- Yamas – how you treat others (honesty, not causing harm, and so on)
- Niyamas – how you treat yourself (self-discipline, contentment)
- Asana – the physical postures
- Pranayama – breathing exercises
- Pratyahara – switching off from outside distractions
- Dharana – focusing your attention
- Dhyana – meditation
- Samadhi – a deep, still state of mind
Originally, the postures weren’t the goal, they were preparation. The old texts describe a good pose simply as one that’s steady and comfortable, nothing more athletic than that. The actual aim of the whole system was training the mind to be calm and focused, and a strong, comfortable body was just what you needed so you could sit still long enough to meditate without your back or your knees interrupting you. A later, more physically detailed text called the Hatha Yoga Pradipika expands on this: it treats the postures, breathing, and cleansing routines as tools for building a healthy, capable body specifically so the mind can do the harder work of meditating. In both texts, the body work exists to serve the mind, not the other way round.
That’s a useful thing to know, because modern science backs up roughly the same idea: the physical and breathing practices measurably calm the nervous system and prepare it for the mental benefits (which we’ll get into below), so the “body first, mind second” structure the ancient texts describe isn’t just philosophy, it shows up in the research too.
Most modern yoga classes only really include two of these eight parts: the postures and, often, some breathing work. That’s not a lesser version of yoga, it’s just one entry point into a much bigger system. “Hatha yoga” specifically refers to that physical side of the practice: postures, breathing, and traditional cleansing routines, all originally intended to prepare the body for meditation.
Asana (the postures)
Asana is what most people picture when they think “yoga,” and it also happens to be the most scientifically studied part. The strongest evidence is for physical, muscle-and-joint benefits, especially with chronic lower back pain. A review of multiple studies found yoga postures produced a meaningful reduction in both pain and disability compared to doing nothing (Cramer et al., 2013). The Cochrane Collaboration, generally considered the gold standard for reviewing medical evidence, reached a similarly positive conclusion (Wieland et al., 2022), and a larger analysis of 18 studies found the pain-reducing effect held up for six to seven months, though it faded after a year (Zhu et al., 2020).
There’s also evidence that regular practice, especially combined with breathing exercises and meditation, lowers the stress hormone cortisol and improves a marker called heart rate variability, essentially a sign that your nervous system is calmer and more resilient (Pascoe, Thompson & Ski, 2017).
Pranayama (breathwork)
Just like yoga asana, pranayama isn’t one single technique, it’s a whole family of specific breathing exercises: slow belly breathing, alternate-nostril breathing, a humming breath called bhramari, and faster, more energising techniques like kapalabhati and bhastrika. Importantly, these don’t all do the same thing to your body.
Slow, controlled breathing has the best evidence behind it. It’s consistently linked to a lower heart rate, lower blood pressure, and improved heart rate variability (Sharpe et al., 2025), all signs your body has shifted into a calmer, “rest and recover” state. Next to this, one study using brain scans found that just four weeks of a specific breathing technique (bhastrika) significantly reduced anxiety, alongside measurable changes in the parts of the brain that process emotion (Novaes et al., 2020).
Kriya (cleansing techniques)
This is the part of Hatha Yoga most in the west never encounter in a studio, a set of traditional cleansing routines described in old yogic texts, intended to physically purify the body before deeper breathing and meditation work. The best known is probably nasal rinsing with saltwater, using a small vessel called a neti pot.
The modern research here is limited but real. That saltwater nasal rinse specifically has decent support: several reviews found it genuinely helps with sinus infections and nasal allergies, working on essentially the same principle as the saline nasal rinses recommended in conventional medicine (Meera et al., 2018). A cleansing technique involving the digestive tract has a small amount of supporting research too, though reviewers are clear that more, better-quality studies are still needed (Swathi, Raghavendra & Saoji, 2021). The rest of these traditional techniques haven’t been rigorously studied by modern science yet, that doesn’t mean they don’t work, just that we don’t have solid evidence either way.
Dhyana (meditation)
Meditation is essentially what’s now studied in the West as “mindfulness,” and it’s one of the most well-researched wellness practices that exists. A large review covering 47 separate studies and over 3,500 people found solid evidence that meditation improves anxiety and depression, and that the benefits were still measurable three to six months later (Goyal et al., 2014). When meditation is combined with yoga postures specifically, a review of nine studies found a meaningful reduction in depression symptoms among people already diagnosed with depression (Miao et al., 2023).
In short
The postures have the strongest evidence for physical benefits, especially back pain. Breathing exercises and meditation have the strongest evidence for calming the nervous system and supporting mental health, arguably the two most worthwhile pieces of the whole system if you’re going by evidence alone. The cleansing techniques are a mixed bag: nasal rinsing has real support, most of the rest simply hasn’t been studied properly yet. And the ethical and personal-conduct parts of yoga aren’t the kind of thing you can test in a lab, they’re the philosophical foundation everything else was originally built on top of.
References
Cramer, H., Lauche, R., Haller, H., & Dobos, G. (2013). A systematic review and meta-analysis of yoga for low back pain. Clinical Journal of Pain, 29(5), 450–460. https://www.journals.lww.com/clinicalpain/abstract/2013/05000/a_systematic_review_and_meta_analysis_of_yoga_for.10.aspx
Goyal, M., Singh, S., Sibinga, E. M. S., et al. (2014). Meditation programs for psychological stress and well-being: A systematic review and meta-analysis. JAMA Internal Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC4142584/
Meera, S., Rani, M. M., Sreedhar, C., & Robin, D. T. (2018). A review on the therapeutic effects of Neti Kriya with special reference to Jala Neti. Journal of Ayurveda and Integrative Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC7329727/
Miao, C., Gao, Y., Li, X., Zhou, Y., Chung, J. W., & Smith, G. D. (2023). The effectiveness of mindfulness yoga on patients with major depressive disorder: A systematic review and meta-analysis of randomized controlled trials. BMC Complementary Medicine and Therapies, 23(1), 313. https://pmc.ncbi.nlm.nih.gov/articles/PMC10492419/
Novaes, M. M., et al. (2020). Effects of yoga respiratory practice (Bhastrika pranayama) on anxiety, affect, and brain functional connectivity and activity: A randomized controlled trial. Frontiers in Psychiatry. https://www.frontiersin.org/journals/psychiatry/articles/10.3389/fpsyt.2020.00467/full
Pascoe, M. C., Thompson, D. R., & Ski, C. F. (2017). Yoga, mindfulness-based stress reduction and stress-related physiological measures: A meta-analysis. Psychoneuroendocrinology, 86, 152–168. https://pubmed.ncbi.nlm.nih.gov/28963884/
Sharpe, E., Lacombe, A., Sadowski, A., et al. (2025). Effectiveness of pranayama for mental disorders: A systematic review and meta-analysis of randomized controlled trials. Frontiers in Psychiatry. https://www.frontiersin.org/journals/psychiatry/articles/10.3389/fpsyt.2025.1616996/full
Swathi, P. S., Raghavendra, B. R., & Saoji, A. A. (2021). Health and therapeutic benefits of Shatkarma: A narrative review of scientific studies. Journal of Ayurveda and Integrative Medicine. https://pmc.ncbi.nlm.nih.gov/articles/PMC8039332/
Wieland, L. S., Skoetz, N., Pilkington, K., Harbin, S., Vempati, R., & Berman, B. M. (2022). Yoga for chronic non-specific low back pain. Cochrane Database of Systematic Reviews, Issue 11. https://www.cochranelibrary.com/cdsr/doi/10.1002/14651858.CD010671.pub3/full
Zhu, F., Zhang, M., Wang, D., Hong, Q., Zeng, C., & Chen, W. (2020). Yoga compared to non-exercise or physical therapy exercise on pain, disability, and quality of life for patients with chronic low back pain: A systematic review and meta-analysis of randomized controlled trials. PLOS ONE. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7462307/
