They have to be 16 in the year of the olympics they perform in. So as long as they turn 16 by 11:59:59 on Dec 31 they are OK.
As for the kid in undies comment, I am not sure what advantage a kid would have over an adolescent, but the rule is there for a reason.
The rules exist for 2 reasons
1) It is for the welfare of the child
2) Younger children have a huge advantage in events like the balance beam and the uneven bars
As for the kid in undies comment, I am not sure what advantage a kid would have over an adolescent, but the rule is there for a reason.”
The younger ones are totally fearless, and they weigh considerably less, so balance is easier.
As gynmasts learn their routines, they grow “muscle memory”. As they mature, their larger breasts and wider hips can change how their routines that they have practiced for years get altered.
Muscle Memory is what gives you the ability to “always be able to ride a bike or a horse” if you ever learned as a kid. I am not saying those muscles are in great shape-—I am just saying “You never forget how to ride a bike or a horse”.