Ashtanga yoga involves poses that flow from one to the next.
However, what sets Ashtanga apart is that you perform the same poses, or asanas, in the same order, for the same breath count, every time you practice. Vinyasa yoga, by comparison, is more flexible involving different poses in various orders.
The full routine, called the primary series, lasts around 90 minutes. Every movement you make has a corresponding inhale and exhale as well as a visual focal point called a Drishti.
