How do you put your hair up for exercise?

Hello curly gurls. After a decade of straightening my hair, I am embracing my natural hair texture and returning to the curly life. A lot of things are very new for me.

My question is, how do you put up your hair for things like the gym? I usually brush it (!) into a bun. This will obviously break up the curls and ruin them. But my hair is too heavy and hot to work out without putting it up. What do?