So this Tara Stiles character sounds obnoxious, but yoga "purists" and "traditionalists" are just the worst, and I say this as a person who counts his daily ashtanga practice as one of the most important parts of his life. Modern posture yoga is of very recent vintage and is a thoroughly synecretic practice that owes as much to imported Western gymnastic, body-building, and gymnastics exercises as it does on mysterious, trance-delivered Vedic texts, as Mark Singleton explains in exhausting detail. (And, oh, by the way, doesn't it strike you as interesting that Tirumalai Krishnamacharya's account of his secret revelation recalls a more classically American scam.) Now, there is no reason to see synecretism as somehow damaging or discrediting; quite the opposite, in fact. Whatever style of yoga you prefer, a regular practice that involves mindfulness, good breath, and physical rigor will improve your comportment and enhance your disposition and certainly give you a well-muscled back and core. My practice changed my life, improved me mentally and physically, gave me better balance and posture, made me stronger, gave me more energy, and it is in large part because of this personal experience that I am so tickled by the authenticity patrol. I mean, shit, even David Swenson puts 15-minute routines in the back of his practice guides.