As for the usefulness of Yoga, there are no longer any doubts; a brief reflection.
Yoga is a practice of psychophysical hygiene of great importance for the conquest and maintenance of health. It is the oldest method of personal growth that involves: body, mind and spirit. Modern medicine has had to surrender to what the ancient oriental masters asserted; it has been demonstrated over and over again by serious research, that Yoga has obvious repercussions on the mind and the body; some of the most important:
It improves the function of the digestive system.
It improves the functionality of the circulatory system.
Improves pulmonary elasticity (diaphragmatic breathing).
Improves the functioning of the endocrine glands.
Improves the elasticity of the muscular system.
It has a marked beneficial influence on the nervous system and the mind.
…from: “Yoga – How to Stay Fit”, by Dr. Aldo Saponaro. Edizioni Della Specola.
Recent discoveries have shown that during Yoga exercises, the brain releases powerful chemical agents: endorphins, morphin-like substances, associated with well-being and therefore anxiolytic. It also helps to “empty” the mind from the usual overload of stimuli. It has a marked beneficial influence on the nervous system and the mind. It is quite evident that mental rebalancing will also have an effect on other body functions, promoting a more balanced metabolism.
As for the aids, I recommend these two excellent texts: “My Yoha exercises” and “Perfection of Yoga” by André Van Lysebeth of Mursia.
Here is the Yoga practice under the eye of experts: