Do you want to get a zero size waist? Do not waste your time trying to do yoga watching the DVD or the TV. Study says all your efforts will go vain as in this exercise, you will not be fit nor in form.

The exercise videos by models, actors in perfect shape would want you to start the exercising right away. But beware, they can be misleading. Exercise is not limited to the body but also needs the mind to be tuned to it. But in terms of exercises performed following the instructions either from a DVD or TV, you will only concentrate on the physical part of it and your mind will be concentrating on the model performing the exercise. 

You should understand that these videos are made after many cuts and retakes. But you will be instructed to practice it at one go. So you will force your body to do whatever is shown on the screen, as a result you will lose the pace and will be stressed, just wanting to complete the asana on time. 

Yoga or any exercise should not be practiced under stress. Instead it should a stress buster. So a study has rightly said that learning through DVDs or TVs is more dangerous than being beneficial. So, take a deep breath, relax and find other ways of learning to exercise.