Check out this video on the Wim Hof breathing method. This is a whole different type of radical breathing exercise. It is very different than the (intentionally passive) mindfulness meditation. The Wim Hof Method is basically controlled hyper-ventilation and it can temporarily suppress the innate immune response as well as temporarily increase heart rate and adrenaline levels. So it’s pretty wicked (in a good way).
There are many variations of the breathing method. The basic version consists of three phases as follows:
Controlled hyperventilation: The first phase involves 30 cycles of breathing. Each cycle goes as follows: take a powerful breath in, fully filling the lungs. Breathe out by passively releasing the breath, but not actively exhaling. Repeat this cycle at a steady pace thirty times. Hof says that this form of hyperventilation may lead to tingling sensations or light-headedness.
Exhalation: After completion of the 30 cycles of controlled hyperventilation, take another deep breath in, and let it out completely. Hold the breath (with lungs empty) for as long as possible.
Breath retention: When strong urges to breathe occur, take a full deep breath in. Hold the breath for around 15 – 20 seconds and let it go. The body may experience a normal head-rush sensation.
These three phases may be repeated for three consecutive rounds.
Check out this guided meditation for your first Wim Hof session:
https://www.youtube.com/watch?v=tybOi4hjZFQ