Take a Breath
Read David Swenson's reply:
There are dangers in prematurely introducing intense pPranayama techniques, such as rapid breathing and prolonged breath retention techniques like Kapalabhati and Bashrika. There is a belief that too much pranayama too soon can overwhelm the nervous system, potentially causing mental or emotional imbalance. The student's nervous system needs to be ready for the immense energy that pranayama can produce.
Practitioners should first strengthen the nervous system through a regulated and consistent asana practice and Ujjayi breathing, with slow introduction of additional pranayama techniques. Students will need to understand the bandhas before they try more advanced pranayama methods. In general, pranayama should be given to the student with care, under the supervision of a teacher qualified to oversee their students' safety and smooth progress.
Kapalabhati is an advanced pranayama technique. Personally, I wouldn't introduce it to a beginner. Instead I would begin with a simple technique such as Ujjayi breathing. By listening to the sound of the breath and becoming intimately aware of the texture and quality of controlled breathing, the student will gain valuable insights. Ujjayi is a safe and effective method that will bring a wonderful awareness to the quality and essence of yogic breathing. The applications of Ujjayi are broad—you can apply it during asana practice or during targeted pranayama.
Pranayama is a powerful and important yogic tool and should be an integral part of a holistic yoga practice—eventually. Begin with more basic methods, and then slowly build toward Kapalabhati and the other more intricate and refined breathing techniques.
David Swenson made his first trip to Mysore in 1977, learning the full Ashtanga system as originally taught by Sri K. Pattabhi Jois. He is one of the world's foremost instructors of Ashtanga Yoga and has produced numerous videos and DVDs. He is the author of the book Ashtanga Yoga: The Practice Manual.