Cameron Diaz: 'I could never run a marathon'

Cameron Diaz fears she'll never be able to run a marathon because of asthma and years of smoking.

The Charlie's Angels star sprints every morning, even when she's on location for a movie, but admits she isn't fit enough to run long-distances.

The actress tells Self magazine, "I sprint seven blocks and sprint back. I'm an interval girl. I had asthma as a child, and I smoked for so long that I just don't have the lung capacity. Speed is my game."

And Diaz admits her lack of endurance ruins work-out sessions with pal Gwyneth Paltrow.

The 41 year old, who has just penned a new healthy lifestyle tome called The Body Book, adds, "I'll only last, like, half of it (session). We enjoy working out together, but she kicks my a**. I don't have her endurance. I'm in awe of her."