Yoga is an internal practice. The rest is just a circus.
Yoga is for internal cleansing, not external exercising. Yoga means true self-knowledge.
Anyone can practice. Young man can practice. Old man can practice. Very old man can practice. Man who is sick, he can practice. Man who doesn't have strength can practice. Except lazy people; lazy people can't practice Ashtanga yoga.
Yoga is 99% practice and 1% theory.
Body is not stiff, mind is stiff.
Yoga is your mind control capacity.