While there are several pranayama practices, they fall into one of two categories. The first is samavritti pranayama–it’s when the inhalation, exhalation, and retention of breath are for the same length. The second is visamavritti pranayama–when the four phases of breath are held for different lengths, normally with an extended exhale. Choosing the appropriate breathing ratio for the task is based on two things: what is possible and what are your goals.