IIRC, many thought that many of the Chinese gymnastic females were underage.
I thought it strange that others would be claiming that, since the Chinese were beating them at most gymnastic competitions.
Younger female gymnists have an advantage because the flexibility of youth is more important than strength in many of their events (not so even for male gymnists esp. on the rings). The international rules making body for gymnastics set a minimum age for international competitions. I don't know of any other event where you would hit your peak at such a young age, but there are many sports where you can get more wins and attention from being the only fifteen year old on a twelve year old team thus the incentive to cheat by claiming a young age.
I did something like that in Little League. All the 9-12 year olds were in one pool with the best in the "major" league and the worst (or youngest) in the "minor" league. I started orginized baseball late (age 12), so I was automatically put in the minor league since it was my first year. I looked like a freak out there with a bunch of 9 and 10 year olds. When I moved up the the 13-15 year group the next year, I learned I wasn't the hottest thing on the field.