Wim Hof - breathing and meditation

[Quan]

I was looking for some methods for helping me to warm my body. I came across tummo breathing and visualisation and Wim Hof method. What bothers me is his breathing technique because he uses forced hyperventilation. This enables divers to hold breath for a longer time but it's also very dangerous, that's why WH warns about doing exercises before swimming, diving ... The effect of such breathing is supposed to be similar to anaesthetic. I don't know if this is the real cause for increased oxygen and heat.

The Wim Hof Method is similar to Tummo (inner heat) Meditation and Pranayama (yogic breathing). Yet it is something else entirely. While Wim has studied yoga and meditation for many years, this technique primordially comes from what he terms ‘cold hard nature’. By subjecting himself to the bitter conditions of nature, he learned to withstand the extreme forces of cold, heat and fear. If you learn this method or technique correctly, it will empower you do to the same.
(highexistence.com)

Swimming and diving he has a different method, in one documenataries he shows it when going underneath an ice sheet in board shorts ... Instead you do the opposite blow out as much air as possible, then breathe in only a little bit and keep repeating.. That way empties all oxygen out then you take a very deep breathe and in this manner can stay under water for a longer time than normal.   However i am not sure what he does before that ..     Ive done the normal technique and also tummo, prana breathing and understand however be better to read from more experienced person can explain a lot better than me, eg him or monks in himalaya and safer too!!  Learn then experiment see what works for you. As he did he learnt tummo then found his own technique that worked for him.