Whether I'm at the or out in the world, when people find out I'm a yoga instructor they often ask me how often they should "do yoga". I have to admit I'm always conflicted in how to answer this question because it isn't as straightforward as one might think.
Usually when people ask, they are asking about the physical practice of yoga, called asana. However, this is just one tiny slice of the meaning of the word yoga, which includes a system of ethical behaviors, breathing techniques, meditation, and other aspects of personal development. Even within the realm of asana, there are many styles and practices, and what frequency might be advisable is dependent on an individual's physical condition and reasons for trying yoga.
The next question, after the aforementioned long, complicated, and undesired response, is usually, "Well, how often do you do yoga?" Unfortunately, I also have no idea how to answer this question! My personal practice is complicated and amorphous, making my answer range from "I teach x hours per week" to "I practice an active yoga style y times per week" to "every breath and every minute."
As an instructor, one generally doesn't count teaching time toward one's personal practice but I also can't ignore the fact I often teach around 10 classes and workshops a week, with varying degrees of activity required. There are many styles of yoga, and they range from physically passive to extremely active. In restorative yoga, students rest and recharge for 10-20 minutes in a few passive poses, supported strategically by blankets and bolsters. In the Iyengar tradition of yoga, which we call "adaptive" at the studio because it focuses on anatomical alignment and adapting the poses to suit the body using props, the student holds individual poses for a long period of time, requiring and building both strength and flexibility. In vinyasa yoga, also called flow yoga, poses are sequenced together in a flowing style with more attention to movement between poses, and the pace may be a fast, cardio-type of class or a gentle, slow dance style. Within and between each of these styles there are variations, including more gentle versions for people recovering from injury or getting back into shape, styles more concerned with spiritual or emotional goals, and more challenging levels for more experienced practitioners. Teaching time, while requiring a lot of physical and mental exertion, doesn't really count as "my yoga practice" even though it does shape it by determining my energy level and physical needs and limits. As a teacher, it is important to me that my primary focus in class be on the student and creating a practice that best meets his or her needs. As a student myself, it is important that I grow in my own study, and a personal practice outside of class is an extremely important part of that process.
In general, a personal practice refers to a period of time a person sets aside to practice yoga on his or her own, and is often a physical practice followed by breathing techniques, called pranayama, and meditation. Traditionally, one is expected to practice yoga regularly, frequently, and diligently. Often texts will suggest setting aside a few hours a day, every day, for personal practice, and strict discipline is one of the fundamental ethical principles. Now, with that being said, I certainly don't manage a 2+ hour practice every morning! Frankly, because I usually work late at night, I don't even manage to do Mornings every morning. Despite this, I would argue I practice yoga every day.
As an example, a little over a week ago I went to a concert. The show was sold out and standing room only. While I stood in the not-quite-sardine packed audience, I was consciously aware of my body. I was aware of where I was spatially in relation to others. I was aware of the sensations coming from my back, my legs, my feet. While enjoying the music I would occasionally slip into a subtle side stretch, or draw my shoulders back and down and pivot at my hip joint to slightly tilt my tailbone for a strong tadasana that released my lumbar spine, or lift my abdomen up into a backbend only my husband would notice (and tease me about later). Over the hours, while the gaps between people ebbed and flowed in that unique, standing-room-only crowd kind of way, I would ease into the newly formed space, coming into a slight tree pose, or coming up on to my toes to stretch the arches of my feet and strengthen my tired ankles, or lowering into a chair pose to strengthen my tired legs. As the energy of the crowd perked up and people started dancing, I was aware of how my active movements released tension from my hips and back. At the end of the show, I wasn't tired from hours of standing at a noisy, crowded live show-- I was invigorated from a quiet, unnoticed practice in a lively, joyful, exuberant atmosphere.
I believe the practice of yoga is more subtle than can be measured merely by how many Sun Salutations I did today. It is a part of my everyday life. People who have met me know I might come into a forward bend or twist in the middle of a conversation because that was what my body needed. I've told people about my secret to subtly practicing triangle and revolved triangle poses on a crowded BART car without 'weirding out' the other commuters. While waiting in lines, I will often stand in tadasana. When caught in bumper to bumper traffic, I practice lion, which I imagine amuses the drivers around me. When I'm stressed, I practice ujjayi or nadi shodhana (alternate nostril) breathing. I constantly evaluate my actions and perceptions in terms of the ethical precepts, including trying and sometimes failing to practice non-violence and truth in word, thought and deed. I believe there are thought patterns and perceptions that hold me back, and I attempt to be conscious of how I interact with the world and detach from those thought patterns and impressions that do not serve me. All of these activities, habits, thoughts, and behaviors constitute my yoga practice. My purpose, however, is to live my yoga as fully as I can right now. Most of my students have less lofty goals.
A lot of my clients are between the ages of 45 and 70 and just want to increase their flexibility, range of motion, and balance. Some want to lose a bit of weight or just feel better when doing physical activities. Many want to manage pain, either from injury or just day-to-day use of their body. A lot of them want techniques to manage stress in their lives because they can feel the physical impact of constant strain, pressure, irritability and impatience. Some of them like the emotional evenness or psychological focus that comes after a practice. This isn't to say they won't someday live their yoga-- after all, I only started because I needed a unit of PE in college, it sounded easy, and I already took bowling in high school.
What all of this does mean is that they are each using yoga to do what they can, with what they have, where they are right now (to borrow from one of Teddy Roosevelt's favorite quotes). Some students can only fit one class into their schedule. Some can't even find the time for a single full-length class and have to come late or leave early. There are instructors who view a late entry or early departure as a sign of disrespect, but so long as the individual is respectful of others and not disruptive, I would rather they get 15 minutes of yoga than none at all. (As a Type A Yogi myself, I am often over-committed and I usually need yoga more on those days I struggle to find time for it.) Students focused on a physical goal with a bit more time may want to do two classes a week, perhaps one really active class and one really gentle class, or to combine three such as a strengthening adaptive class, then a faster-paced, flowing vinyasa class, and then a meditative or restorative class for general conditioning. I would rather students listen to their own body and avoid the urge to push themselves past what is safe and healthy for them physically than rush into a daily, active practice that might result in injury, frustration or dejection. All of these students are finding their own way into their own practice.
At the end of the day (this isn't a cliche-- I just assume it took a whole day to read this lengthy post), I suppose I really only have one answer to the question "How often should I do yoga?": Your yoga is your yoga, however you come by it. It isn't my job to tell you what your yoga looks like; it is my job to help you decide what your yoga looks like for yourself, and to facilitate your practice in whatever ways I can.