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You could say Chau Smith is in good shape. The 70-year-old Missouri woman recently ran seven marathons on seven continents in seven days. Dubbed the "Triple 7 Quest," the challenge saw her pound 26.2 miles a day across Australia, Singapore, Egypt, the Netherlands, the U.S., Chile, and Antarctica. Smith, who works 10 hours a day at her dry cleaning business, says she found the experience invigorating. "I live a stressful life," she says. But after a run, "I always feel better."

Smith is now planning to hike the Appalachian Trail.