Breathing

Large pearls of sweat were rolling down Foster's forehead and bare chest. He had taken off his shirt and the jacket of his gi, since his whole body was sort of heating up as he was in the middle of this. Or well, at least part of his body was. Right now, Foster only managed to get started on the flow of mana within his arms and legs. And it was only a one-directional flow, even then. He was just moving the mana out of his limbs the way that the book told him to. But just that was enough for his body to feel like he was sitting in a sauna.

According to the book, that was just a normal side effect of setting up an incomplete flow of mana. Luckily, that also meant that he would have a direct way of knowing when he managed to establish the intended flow.