Yoga breathing exercises are called pranayama techiniques.

This word can be broken down into two parts:
Prana means life force -Yama means control.

Pranayama breathing exercises are the link between the physical and mental disciplines of yoga.
Because the breath, body and mind are so closely linked, a change in one immediately affects the other two.

By developing the control of your breath you can bring about beneficial changes in your body and mind.
The breath unifies mind and body and helps in relaxing into the various poses of yoga.
The more relaxed you become, the more flexible you will become.