I just want to add that I think parents who have small children and are into sports and such tend to seek out a sport that would meet the attributes that their child possesses, like small kids tend to do gymnastics, not basketball or volleyball. Kids who tend to be small quite possibly have delayed growth to begin with. I'm not saying that gymnastics stunts their growth, I'm saying these kids would of been delayed regardless of what they did.
My kid is a prime example of what I'm talking about. She was small and constantly being checked by doctor's to make sure there was nothing wrong with her. I am 5'3", dh is 5'6", yeah I know we just scream tall! At 5yrs old she had a bone age scan and it showed that although she was chronologically 5 yrs old, her actual bone age was that of a 3.5 yr old. So her body was 1.5 yrs behind her actual age. We continued to monitor. At 12, she had another bone age scan and at 12, her bone age was that of a 9 yr old. So, around 11-12 yrs old is when the standard growth charts start to soar up as that is when puberty hits many kids. So that is why when she fell off the charts the Primary again flipped out and we were off to the Endocrinologist (that is who does the bone age scan, not a Primary). This helps to explain a lot. So many girls are having growth spurt at the age of 11/12 and my kids till looks like a 9 yr old. No signs of puberty, but why would there be if her body is still showing signs of a 9 yr old, not 12 yr old. When my dd went off to high school, she looked like a 12 yr old her freshman year. She did do a whole transformation while in her freshman year and she finally looked like a teenager when she started her sophomore yr. Realize that my kid went through puberty from the age of 14-15.5, which again makes sense when you keep in mind the results of her last bone scan. Honestly, gymnastics wasn't stunting her growth, she was just delayed to begin with. She did get her period right before she turned 16.
She is now in college and guess what, she is small, very petite (not only in size, which by the way she is about 5'1") but she doesn't look like she is 12 anymore. She looks young for her age, but I told her she will come to love that when she is 30 years old!