On my birthday last year (with the help of liquid courage) I believed I could still do the splits. I also believed I could do them quickly and on concrete floor. I went down hard on my left thumb. To this day, nearly a year later, it hurts pretty good to put any pressure on it (like if I were to try to crack my knuckles, I would not try with that thumb) and it no longer moves as freely as my other thumb. Whoops!