Hey
This is the reason for me getting involved in lucid dreaming. I'm a musician (classical) and I am certain that it is possible to practise your instrument in your sleep. Its more about creating neural connections than having physical "ability". I think one way of proving this is: go to a piano (it doesn't matter if you cant play) and in your left hand only, invent a melody that is difficult for you to play. do this a few times, speed it up until it is of a much higher standard than when you first played. now try to play it in your right hand. You'll probably play it perfectly, or at least of a much higher standard than your original left handed attempt.
Its not a huge stretch of imagination to apply this concept to sports, or even studying for exams etc.
I hope this is of use
on an unrelated note... i had my first lucid dream last night, but got too excited and woke up within 30 seconds... just felt like saying it haha