Serena Williams traded in the tennis court for the track over the weekend, competing with her sister Venus in Miami's quarter-marathon Ultimate Run. Serena served as host of the run.

Serena could be seen sporting a chic pair of black Nike micro shorts and looking fast and fit as ever. Proceeds from the charity run were directed toward the Serena Williams Fund, which provides aid and assistance to victims of violent crimes. The organization also provides funding for two schools in Kenya.

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'People love it. You can run, walk, bring your family, it's early in the morning," Williams said at the event, per the Daily Mail. "I like running the shorter distances, like 5K. You don't kill your body, but you can still feel part of the race atmosphere."

In addition to just gaining enjoyment from the run, Williams credited it as a key component of her tennis training. "It definitely helps your endurance on the court,' she said. 'You feel you can run so many miles, you can last three hours, four hours if you need to."

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After the race, the Williams sisters even cut loose with a little karaoke on the beach. You can watch footage of the inaugual Serena Williams Ultimate Run below. And head over to Daily Mail to see a host of great photographs from the event.