DEFFUZZ, that's a common concern, but fortunately, it's not one you have to worry about. You are female, therefore you are simply not likely to bulk up! This article explains the difference between toning and bulking up, and why you do NOT need to be afraid of weight lifting, and lifting heavy at that. In addition to being female, you can't gain muscle because you are eating at a calorie deficit! www.sparkpeople.com/resource/fitness_artic
Yoga has many benefits, among them all that you've listed, but it is not not an adequate substitute for strength training. It's flexibility and stress-reducing, improves balance, and can provide some strength benefits in the early parts of your training, but does not challenge your body the way true strength training does. Increasing strength and increasing muscle mass are not the same thing. In order to "bulk up", you need to lift like a body builder, and eat like one, too: at a calorie surplus. While eating at a deficit, the most you can hope for is to preserve the muscle you do have. Like Jen, I'm not certain that yoga is strenuous enough for you to even manage that.
Yoga will not develop "long, lean" muscles as they claim; it can't really help with that, and there's no way to lengthen muscles, anyway! It's very beneficial, and as a fellow practitioner myself, I strongly recommend it to anyone who will listen. But I still lift weights, and will always lift weights. They serve two different, entirely compatible, goals.
Here's another article that will help: www.sparkpeople.com/resource/fitness_artic
Edited by: DRAGONCHILDE at: 2/5/2013 (17:06)