Tennis superstars Venus and Serena Williams are showing off their tight abs on the cover of New York Times Magazine.

Both sisters have been known to cause plenty of controversy on the tennis court.

Serena tells the mag:

    "Every year at the Open something happens. Like last year I got a point penalty because of a grunt. Meanwhile, I can name five girls who grunt way louder than I do, and the umpire didn’t even give them a warning. And then I had the ball called out that was this far in. It’s always something.”

Sounds like the Williams sisters are not to be messed with!