I like the one on cafe press for parents, "I'm driving like a nut right now because I have to get my daughter to gymnastics"
I also enjoy:
"I heart conditioning"
"Life is like gymnastics. It's better if you're flexible."
"Jump off the beam, flip off the bars, follow your dreams, and reach for the stars."
Front-"after a day of football, a gymnast would be bruised..." Back-"After a day of gymnastics a football player would be dead."
"Have you hugged a gymnast lately?"
"No time outs, no halftime, no overtime"
"Don't cha...wish your girlfriend was a gymnast like me?"