It's probably a bit off topic, but... My younger brother hits a racketball really hard. You do NOT want to be in the path of his kill shot.

I watched him warm up, hitting a new ball repeatedly very hard, and it broke in half, as did the next one.

He explained that in a game, they have time to cool down and rarely break, but it's easy to break one in a warmup as the heat builds. (easy provided you have the technique to hit it hard enough) The local gym had a 2 for 1 replacement policy on broken balls, so he always had free new balls.

Do piano strings get hot?

gotta go practice