Why not pray to a Patron saint of Athletes, St. Sebastian?
saints.sqpn.com/saint-sebastian/
I highly doubt you will find one saint SPECIFIC for gymnastics.
Btw, this might not be much relevant, but once I went to a massive veneration of Relics of saints. One of the speakers, a priest, told us that each person has a patron saint. So this is the saint that God has given us in a
special way to pray on our behalf (not that others don’t pray). When you need something, you don’t have to necessarily go looking for who the patron saint for it. You could just pray to YOUR patron saint.
How do you know this patron saint?
In the case of that specific event, he said it is someone who you would feel very deeply connected to as you venerate and read about their life. Some people get a sign like a burning when they touch the relics etc.
But in short, rather than look for a patron saint for the specific sport, it might be better for you to pray to your Patron saint as well.
