Fitness legend Arnold Schwarzenegger has taken on bodybuilding, Hollywood, even politics. Now he's facing a bigger battle than "The Terminator" or "Predator" — how to age gracefully.

At 78, his days of death-defying stunts might be over. Schwarzenegger told Business Insider that he has accumulated more than his share of aches and injuries over time, due to skiing accidents, long hours in the gym, and intense action films.

"That's a lot of stress on a body and clearly the body was not meant to do all that," he said.

But the star is no less active in the gym and in the public eye, in part because he's kept his diet and exercise on point over the years. His recent projects incuded the release of his book "Be Useful," a hit Netflix docuseries, and the launch of his own fitness app "The Pump

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