What is the name of this bowing technique for strings?

Butterfly technique is all about balance. A lot of propulsion is generated from undulation but too much undulation means you will spend most your energy going up and down. 🚨Use the breath to generate forward momentum🚨 Here you can see how @noeponti breathes super low. His chin is skating across the surface and it probably reminds you of the iconic pictures of @m_phelps00 swimming butterfly. This requires incredible flexibility and timing of your kick, pull and breath. It’s easy to over emphasi