it is indeed possible.

there are some sleep laboratories which train sportsmen to get a better condition - the results are awesome.

some time ago they mentionend in the television an athlete who trained in his dream - he was a jumper.
in his dream he always jumped higher and further and the more he trained his skills in his dreams the better he became in the real world

here is a page about the whole stuff concerning sports and LDīs
www.klartraum.de (German site)