 And we generate heat just through our metabolism. But it's interesting that sort of 80% of the energy produced by working muscles is heat. So that has to be dissipated. And when you have temperatures outside the human body, the ambient temperature that's getting close to that, then it's really difficult to shed that extra heat. And so if we can't shed it, we store it. And as you know, when your temperature gets to about 38, you start feeling pretty ordinary.