The title should actually read:
"Grunting in tennis diminishes your opponents game"
You don't get better, your opponent gets worse.

The paper that this article links to makes all sorts of claims about extra-terrestrial origins for these cells. However, a simple wikipedia search for the red rain in question reveals that, whilst people were initially confounded about the origins of the red rain, it has been since confirmed that the red 'cells' in the rain are actually spores from moss and lichen.

Seems to me like some biologists wanted to sexy-up a piece of otherwise boring research in order to get some press.