This is a very interesting topic. I have 3 kids all involved in sports - irish dancing, GAA football, hurling, swimming and gymnastics.
My DD aged 10 and DS aged 7 are really good irish dancers. Their teacher said they both have a natural talent for it, DD does this flick with her ankle in hard shoe dancing that her teacher says you either have or don't, its too hard to teach it. They both have a talent for musical timing but this is something I think that can be taught easier.
She told me that there are a couple of dances with very tricky timing that takes most kids ages to learn. DD and only one or two other kids were able to get this timing immediately. That being said DD doesn't practise and doesn't have that drive and kids who are not as naturally talented are much better than her because they put hours of practise into it.
DS2 is naturally very good at all sports, he is performing really well in all the sports he does and is moving through the levels much quicker than his siblings, but he loves to practise!
DS1 is very academic but not talented in sports. He is clumsy, he has no 3d vision so struggles to catch a ball (twofishfingers I am definitely going to get him to try juggling!). He is not overweight at all but is broad and big boned unlike the other two who are very slim. He wont take direction, if I try to give him advice he will argue with me all day long. When he puts his mind to something he achieves so much and I know if he put more effort into the work he would be much better. He loves sports and I do think that at some point it will all click for him.
It is heartening to hear the stories about kids who started out not being good but ended up much better. It definitely shows that practise does pay off.