What are the yellow sparks that appear under certain Pokemon?

Question

In Black/White, when certain Pokemon are sent into battle some yellow sparks come out from underneath their feet. It seems like it's mostly large and heavy Pokemon and the sparks appear as they land.

I have seen it on Boldore/Gigalith, Scolipede, Golurk, Emboar and possible some of the dragons. I think it may only be trainer battles, not those in the wild.

Do they mean anything in particular?

Answer 1

They mean that the pokemon is on the heavy side.
light pokemon don't do it,
mid-weights just shake the screen,
and heavy-weights make sparks, or dust as I call it.

Comments

It also is so you can judge the effectiveness of moves like grass knot.