In yoga it is known that we use body & breath to improve our state of being .
Yes there are movements explorations and postures where we can increase our strenght and flexibility, find relief for back pain , reduce our stress level.. and all matters where research and yoga go well together.
However yoga should not be limited to this.
I think yoga gives us a different view of the world than that cultivated on our left brain and materialistic approach to life.
Both are needed for a fullfilled existence : Matter & Spirit .