Please, please, please don't try this at home. In this clip, a Lithuanian brother-sister team, both illusionists, goes for a few breath-holding records—the significant one appears to be thirteen minutes and 42 seconds at the start. To hold your breath for a long time, you need to slow your heartbeat significantly. If your heart's not working as hard, then it's not going to burn up the limited supply of oxygen in your blood as quickly. In the same way, the less you do while holding your breath, the better. Eventually, when things start getting ugly, the heart stops sending as much oxygen to the extremities, and focuses on keeping the vital organs stocked with blood. Obviously this pair is keeping these points in mind: You can see that the twins are completely relaxed, their faces not even moving, throughout most of the video.