Considering Yoga only as a fitness activity is like valuing a diamond as a piece of glass.
Definition of Yoga:
Yoga Chitta Nirodha
Stoppage of flickering of the mind. Yoga is to achieve equanimity in pain & pleasure, happiness & sorrow.
“ġham aur ḳhushī meñ farq na mahsūs ho jahāñ,maiñ dil ko us maqām pe laatā chalā gayā.”(Film: Hum Dono, Lyrics: Sahir Ludhianvi)
This is the true practice of Yoga. This is a 24 x 7 activity.
For those who are interested in the history of Yoga, here is an interesting film. This film depicts the Indian history of 6000 years.